title:
Inclusive transverse momentum distributions of charged particles in
  diffractive and non--diffractive photoproduction at HERA

abstract:
  Inclusive transverse momentum spectra of charged particles in photoproduction
events in the laboratory pseudorapidity range $-1.2<\eta<1.4$ have been
measured up to $p_{T}=8\GeV $ using the ZEUS detector. Diffractive and
non--diffractive reactions have been selected with an average $\gamma p$ centre
of mass (c.m.) energy of $\langle W \rangle = 180\GeV$. For diffractive
reactions, the $p_{T}$ spectra of the photon dissociation events have been
measured in two intervals of the dissociated photon mass with mean values
$\langle M_{X} \rangle = 5$ GeV and $10$ GeV. The inclusive transverse momentum
spectra fall exponentially in the low $p_{T}$ region. The non--diffractive data
show a pronounced high $p_{T}$ tail departing from the exponential shape. The
$p_{T}$ distributions are compared to lower energy photoproduction data and to
hadron--hadron collisions at a similar c.m. energy. The data are also compared
to the results of a next--to--leading order QCD calculation.


title:
Measurement of the Cross Section for the Reaction $\gamma p \to \jpsi~p$
  with the ZEUS Detector at HERA

abstract:
  This paper reports the cross section measurements for the process ep
$\rightarrow$ e~\jpsi~p for $Q^2 < 4$ GeV$^2$ at $\sqrt s = 296$ GeV, based on
an integrated luminosity of about 0.5~pb$^{-1}$, using the ZEUS detector. The
\jpsi~was detected in its $\rm e^{+}e^{-}$ and $\rm \mu^{+}\mu^{-}$ decay
modes. The photoproduction cross section was measured to be $52^{ \
+7}_{-12}\pm 10$~nb at an average $\gamma$p centre of mass energy of 67 GeV and
$71^{+13}_{-20}\pm 12$~nb at 114 GeV. The significant rise of the cross section
compared to lower energy measurements is not in agreement with VDM models, but
can be described by QCD inspired models if a rise in the gluon momentum density
at low $x$ in the proton is assumed.


title:
Measurement of Charged and Neutral Current $e^-p$ Deep Inelastic
  Scattering Cross Sections at High $Q^2$

abstract:
  Deep inelastic $e^-p$ scattering has been studied in both the charged-current
(CC) and neutral-current (NC) reactions at momentum transfers squared, $Q^2$,
between 400 GeV$^2$ and the kinematic limit of 87500 GeV$^2$ using the ZEUS
detector at the HERA $ep$ collider. The CC and NC total cross sections, the NC
to CC cross section ratio, and the differential cross sections, $ d\sigma/dQ^2
$, are presented. For $Q^2 \simeq M_W^2$, where $M_W$ is the mass of the $W$
boson, the CC and NC cross sections have comparable magnitudes, demonstrating
the equal strengths of the weak and electromagnetic interactions at high $Q^2$.
The $Q^2$ dependence of the CC cross section determines the mass term in the CC
propagator to be $M_{W} = 76 \pm 16 \pm 13$~GeV.


title: First Results from the BELLE DIRC Prototype

abstract:
  The DIRC (Detection of Internally Reflected Cerenkov light) is a new type of
ring imaging Cerenkov detector, which detects images from Cerenkov light
produced in precisely machined quartz bars. The Cerenkov images are transported
along several meters of bar to the edge of the detector where they are
proximity focussed unto an array of conventional photomultiplier tubes. Results
from a prototype device comprising a 2 x 4 x 240 cm**3 quartz bar read by an
array of 480 PMT's are presented. Sample images, which are the first observed
in this type of detector, are shown. Measurements of the light yield
(approximately 20 photoelectrons per image) and the angular resolution are in
good agreement with Monte Carlo predictions.


title: The Structure Function Ratios F2(Li)/F2(D) and F2(C)/F2(D) at small x

abstract:
  We present the structure function ratios F2(Li)/F2(D) and F2(C)/F2(D)
measured in deep inelastic muon-nucleus scattering at a nominal incident muon
energy of 200 GeV. The kinematic range 0.0001 < x < 0.7 and 0.01< Q^2 < 70
GeV^2 is covered. For values of $x$ less than $0.002$ both ratios indicate
saturation of shadowing at values compatible with photoabsorption results.


title: Observation of the beam-size effect at HERA

abstract:
  A precise measurement of the spectrum of the photons from $ep$ bremsstrahlung
with the ZEUS luminosity monitor at HERA is reported. The measurement shows a
reduced rate compared to the Bethe-Heitler spectrum for photon energies below
5~GeV. This suppression, called the beam-size effect, is explained by the
finite transverse size of the beam overlap relative to the typical impact
parameter in the process of $ep$ bremsstrahlung at HERA energies.


title: Inclusive Parton Cross Sections in Photoproduction and Photon Structure

abstract:
  Photoproduction of 2-jet events is studied with the H1 detector at HERA.
Parton cross sections are extracted from the data by an unfolding method using
leading order parton-jet correlations of a QCD generator. The gluon
distribution in the photon is derived in the fractional momentum range $0.04\le
x_\gamma \le 1$ at the average factorization scale $75$ GeV$^2$.


title: A Measurement of the Branching Ratio and Form Factor of K_L->mu mu gamma

abstract:
  We report on a measurement of the decay $K_L\rightarrow\mu^+\mu^-\gamma$ from
Fermilab experiment E799. We observe $207$ candidate signal events with an
estimated background of $10.5 \pm 4.0$ events and establish
$B(K_L\rightarrow\mu^+\mu^-\gamma) = (3.23\pm 0.23(stat) \pm 0.19(sys))\times
10^{-7}$. This provides the first measurement of the $K\gamma\gamma^*$ form
factor in the muonic Dalitz decay mode of the $K_L$.


title:
WOPPER, Version 1.3: A Monte Carlo Event Generator for e+ e- -> W+ W- ->
  4f + n gamma at LEP2 and beyond

abstract:
  We describe the Monte Carlo event generator WOPPER for four fermion
production through W-pairs including resummed leading logarithmic QED radiative
corrections.


title: hepawk, Version 1.6: A Language for Scanning High Energy Physics Events

abstract:
  This manual describes version 1.6 of the programming language hepawk,
designed for convenient scanning of data structures arising in the simulation
of high energy physics events. The interpreter for this language has been
implemented in FORTRAN77, therefore hepawk runs on any machine with a FORTRAN77
compiler.


title:
Leptoquarks and Compositeness Scales from a Contact Interaction Analysis
  of Deep Inelastic $e^\pm \, p$ Scattering at HERA

abstract:
  A contact interaction analysis is presented to search for new phenomena
beyond the Standard Model in deep inelastic $e^\pm p \rightarrow e^\pm \,
hadrons$ scattering. The data are collected with the H1 detector at HERA and
correspond to integrated luminosities of $0.909 \ {\rm pb}^{-1}$ and $2.947 \
{\rm pb}^{-1}$ for electron and positron beams, respectively. The differential
cross sections $d\sigma / dQ^2$ are measured in the $Q^2$ range bet\-ween $160
\ \GeV^2$ and $20,000 \ \GeV^2$. The absence of any significant deviation from
the Standard Model prediction is used to constrain the couplings and masses of
new leptoquarks and to set limits on electron--quark compositeness scales and
on the radius of light quarks.


title: Results from the LSND Neutrino Oscillation Search

abstract:
  The Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos Meson
Physics Facility sets bounds on neutrino oscillations in the appearance channel
nu_mu_bar --> nu_e_bar by searching for the signature of the reaction nu_e_bar
p --> e^+ n: an e$^+$ followed by a 2.2MeV gamma ray from neutron capture. Five
e^{+/-} -- gamma coincidences are observed in time with the LAMPF beam, with an
estimated background of 6.2 events. The 90\% confidence limits obtained are:
  Delta (m^2) < 0.07eV^2 for sin^2 (2theta) = 1, and sin^2(2theta) < 6 10^{-3}
for Delta (m^2) > 20 eV^2.


title: A liquid-helium cooled large-area silicon PIN photodiode x-ray detector

abstract:
  An x-ray detector using a liquid-helium cooled large-area silicon PIN
photodiode has been developed along with a tailor-made charge sensitive
preamplifier whose first-stage JFET has been cooled. The operating temperature
of the JFET has been varied separately and optimized. The x- and $\gamma$-ray
energy spectra for an \nuc{241}{Am} source have been measured with the
photodiode operated at 13 K. An energy resolution of 1.60 keV (FWHM) has been
obtained for 60-keV $\gamma$ rays and 1.30 keV (FWHM) for the pulser. The
energy threshold could be set as low as 3 keV. It has been shown that a silicon
PIN photodiode serves as a low-cost excellent x-ray detector which covers large
area at 13 K.


title: Study of the photon remnant in resolved photoproduction at HERA

abstract:
  Photoproduction at HERA is studied in $ep$ collisions, with the ZEUS
detector, for $\gamma p$ centre-of-mass energies ranging from 130-270 GeV. A
sample of events with two high-$p_T$ jets ($p_T > 6$ GeV, $\eta <1.6$) and a
third cluster in the approximate direction of the electron beam is isolated
using a clustering algorithm. These events are mostly due to resolved
photoproduction. The third cluster is identified as the photon remnant. Its
properties, such as the transverse and longitudinal energy flows around the
axis of the cluster, are consistent with those commonly attributed to jets, and
in particular with those found for the two jets in these events. The mean value
of the photon remnant $p_T$ with respect to the beam axis is measured to be
$2.1 \pm 0.2$ GeV, which demonstrates substantial mean transverse momenta for
the photon remnant.


title: An Ultrahigh-Statistics Charm Experiment for the Year $\sim2000$

abstract:
  After reviewing the motivation for high-statistics charm studies, we describe
a fixed-target experiment capable of reconstructing $>10^8$ charm decays. Such
an experiment can test the Standard Model and probe non-Standard physics
through sensitive searches for such phenomena as D0 mixing, CP violation, and
FCNC decays.


title: A Study of the Fragmentation of Quarks in $e^-p$ Collisions at HERA

abstract:
  Deep inelastic scattering (DIS) events, selected from 1993 data taken by the
H1 experiment at HERA, are studied in the Breit frame of reference. The
fragmentation function of the quark is compared with those of \ee data. It is
shown that certain aspects of the quarks emerging from within the proton in \ep
interactions are essentially the same as those of quarks pair-created from the
vacuum in \ee annihilation. The measured area, peak position and widthof the
fragmentation function show that the kinematic evolution variable, equivalent
to the \ee squared centre of mass energy, is in the Breit frame the invariant
square of the four-momentum transfer. We comment on the extent to which we have
evidence for coherence effects in parton showers.


title: Neural Network based Electron Identification in the ZEUS Calorimeter

abstract:
  We present an electron identification algorithm based on a neural network
approach applied to the ZEUS uranium calorimeter. The study is motivated by the
need to select deep inelastic, neutral current, electron proton interactions
characterized by the presence of a scattered electron in the final state. The
performance of the algorithm is compared to an electron identification method
based on a classical probabilistic approach. By means of a principle component
analysis the improvement in the performance is traced back to the number of
variables used in the neural network approach.


title:
Momentum Correlations of Charmed Pairs Produced in $\pi^{-}-Cu$
  Interactions at 230 GeV/c

abstract:
  We study the production characteristics of 557 pairs of charmed hadrons
produced in $\pi^{-}-Cu$\ interactions at 230~GeV/c using a momentum estimator
for charmed hadrons with missing decay products. We find, the mean value of the
transverse momentum squared of the charmed pairs is $<$\pts$>=(1.98\pm 0.11\pm
0.09)\;$ GeV$^2$/c$^2$, the mean rapidity difference is $<|$\yd$|>=0.54\pm
0.02\pm 0.24$, and the mean effective mass is $<$\mef$>=(4.45\pm 0.03\pm
0.13)\;$ GeV/c$^2$. Comparing these results with the next-to-leading order QCD
predictions we find an agreement for the \yd\ and \mef, whilst the measured
mean value of \pts\ is significantly larger than the predicted value.


title:
Shadowing in Inelastic Scattering of Muons on Carbon, Calcium and Lead
  at Low XBj

abstract:
  Nuclear shadowing is observed in the per-nucleon cross-sections of positive
muons on carbon, calcium and lead as compared to deuterium. The data were taken
by Fermilab experiment E665 using inelastically scattered muons of mean
incident momentum 470 GeV/c. Cross-section ratios are presented in the
kinematic region 0.0001 < XBj <0.56 and 0.1 < Q**2 < 80 GeVc. The data are
consistent with no significant nu or Q**2 dependence at fixed XBj. As XBj
decreases, the size of the shadowing effect, as well as its A dependence, are
found to approach the corresponding measurements in photoproduction.


title:
Measurement of the $WW\gamma$ gauge boson couplings in $p\bar{p}$
  Collisions at $\sqrt{s}=1.8$ TeV

abstract:
  The $WW\gamma$ gauge boson couplings were measured using $p\bar{p}\to
\ell\nu\gamma+X$ ($\ell=e,\mu$) events at $\sqrt{s}=1.8$ TeV observed with the
{D\O} detector at the Fermilab Tevatron Collider. The signal, obtained from the
data corresponding to an integrated luminosity of $13.8 {\rm pb}^{-1}$, agrees
well with the Standard Model prediction. A fit to the photon transverse energy
spectrum yields limits at the 95% confidence level on the CP--conserving
anomalous coupling parameters of $-1.6<\Delta\kappa<1.8$ ($\lambda$ = 0) and
$-0.6<\lambda<0.6$ ($\Delta\kappa$ = 0).


title: $W\gamma$ and $Z\gamma$ Production at Tevatron

abstract:
  We present results from CDF and D\O\ on $W\gamma$ and $Z\gamma$ productions
in $p\bar{p}$ collisions at $\sqrt{s}=1.8~{\rm TeV}.$ The goal of the analyses
is to test the non-abelian self-couplings of the $W$, $Z$ and photon, one of
the most direct consequences of the $SU(2)_L\otimes U(1)_Y$ gauge symmetry. We
present direct measurements of $WW\gamma$ couplings and limits on $ZZ\gamma$
and $Z\gamma\gamma$ couplings, based on $p\bar{p}\rightarrow \ell\nu\gamma + X$
and $p\bar{p}\rightarrow \ell\ell\gamma+X$ events, respectively, observed
during the 1992--1993 run of the Fermilab Tevatron Collider.


title: Charm and Beauty Results from CDF and D0

abstract:
  Reporting, for the CDF and D0 collaborations, results from the 1992-93
Fermilab Tevatron Collider run concerning charm and beauty quark production and
beauty meson decay properties.


title:
Measurement of the diffractive structure function in deep inelastic
  scattering at HERA

abstract:
  This paper presents an analysis of the inclusive properties of diffractive
deep inelastic scattering events produced in $ep$ interactions at HERA. The
events are characterised by a rapidity gap between the outgoing proton system
and the remaining hadronic system. Inclusive distributions are presented and
compared with Monte Carlo models for diffractive processes. The data are
consistent with models where the pomeron structure function has a hard and a
soft contribution. The diffractive structure function is measured as a function
of $\xpom$, the momentum fraction lost by the proton, of $\beta$, the momentum
fraction of the struck quark with respect to $\xpom$, and of $Q^2$. The $\xpom$
dependence is consistent with the form \xpoma where
$a~=~1.30~\pm~0.08~(stat)~^{+~0.08}_{-~0.14}~(sys)$ in all bins of $\beta$ and
$Q^2$. In the measured $Q^2$ range, the diffractive structure function
approximately scales with $Q^2$ at fixed $\beta$. In an Ingelman-Schlein type
model, where commonly used pomeron flux factor normalisations are assumed, it
is found that the quarks within the pomeron do not saturate the momentum sum
rule.


title: Neutral strange particle production in deep inelastic scattering at HERA

abstract:
  This paper presents measurements of \k\ and \lam\ production in neutral
current, deep inelastic scattering of 26.7 GeV electrons and 820 GeV protons in
the kinematic range $ 10 < Q^{2} < 640 $ GeV$^2$, $0.0003 < x < 0.01$, and $y >
0.04$. Average multiplicities for \k\ and \lam\ production are determined for
transverse momenta \ \ptr\ $> 0.5 $ GeV and pseudorapidities $\left| \eta
\right| < 1.3$. The multiplicities favour a stronger strange to light quark
suppression in the fragmentation chain than found in $e^+ e^-$ experiments. The
production properties of \k's in events with and without a large rapidity gap
with respect to the proton direction are compared. The ratio of neutral \k's to
charged particles per event in the measured kinematic range is, within the
present statistics, the same in both samples.


title:
A Study of Hadronic Backgrounds to Isolated Hard Photon Production with
  L3

abstract:
  I describe two methods for studying hadronic backgrounds to prompt photon
production with L3, and compare the observed background rates with Monte Carlo
predictions. I find that the Monte Carlo models JETSET and HERWIG underestimate
the production of isolated neutral hadrons in hadronic Z decays at LEP. By
extrapolating results obtained with L3, I estimate that the rate of
prompt-photon + jet background to a H -> gamma gamma search at the LHC will be
larger than Monte Carlo predictions by a factor of 1.5-2.5.


title: W and Z Boson Production in PbarP Collisions at Sqrt(s)=1.8 TeV

abstract:
  The inclusive cross sections times leptonic branching ratios for W and Z
boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the
D0 detector at the Fermilab Tevatron collider:
  Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb,
  Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb,
  Sigma_Z*B(Z-> e, e) = 0.218 +/- 0.011 +/- 0.012 nb,
  Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb.
  The first error is the combined statistical and systematic uncertainty, and
the second reflects the uncertainty in the luminosity. For the combined
electron and muon analyses we find:
  [Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49.
  Assuming Standard Model couplings, this result is used to determine the width
of the W boson:
  Gamma(W) = 2.044 +/- 0.093 GeV.


title: A Direct Determination of the Gluon Density in the Proton at Low x

abstract:
  A leading order determination of the gluon density in the proton has been
performed in the fractional momentum range $1.9 \cdot 10^{-3} < x_{g/p} < 0.18$
by measuring multi-jet events from boson-gluon fusion in deep-inelastic
scattering with the H1 detector at the electron-proton collider HERA. This
direct determination of the gluon density was performed in a kinematic region
previously not accessible. The data show a considerable increase of the gluon
density with decreasing fractional momenta of the gluons.


title: The Gluon Density of the Proton at Low $x$ from a QCD Analysis of $F_2$

abstract:
  We present a QCD analysis of the proton structure function $F_2$ measured by
the H1 experiment at HERA, combined with data from previous fixed target
experiments. The gluon density is extracted from the scaling violations of
$F_2$ in the range $2\cdot 10^{-4}<x<3\cdot 10^{-2}$ and compared with an
approximate solution of the QCD evolution equations. The gluon density is found
to rise steeply with decreasing $x$.


title:
Measurement of the $e^+$ and $e^-$ induced charged current cross
  sections at HERA

abstract:
  The cross sections for the charged current processes
${e^{-}p}\rightarrow{\nu_e+hadrons}$ and, for the first time,
${e^{+}p}\rightarrow{\overline{\nu}_e+hadrons}$ are measured at HERA for
transverse momenta larger than 25 GeV.


title: CDF Results on $B$ Decays

abstract:
  We present recent CDF results on $B$ lifetimes, $B$ meson mass measurements,
ratios of branching ratios, and rare decays. In addition, we present the first
measurement of time-dependent $B_d$ mixing at CDF. Several results have been
updated and a few new ones included since the workshop.


title: Measurement of the Tau Lifetime at SLD

abstract:
  A measurement of the lifetime of the tau lepton has been made using a sample
of 1671 $Z^0\rightarrow\tau^+\tau^-$ decays collected by the SLD detector at
SLC. The measurement benefits from the small and stable collision region at SLC
and the precision vertex detector of SLD. Three analysis techniques have been
used: decay length, impact parameter, and impact parameter difference methods.
The combined result is $\tau_\tau = 297\pm 9(stat.)\pm 5(syst.)$ fs.


title:
Jet production in $\gamma\gamma$ collisions at TRISTAN with the TOPAZ
  detector

abstract:
  Jet production in $\gamma \gamma$ collisions have been studied with a
jet-cone algorithm using a 233 $pb^{-1}$ data taken by the TOPAZ detector at
the TRISTAN $e^+e^-$ collider. The transverse momentum dependence of the
jet-cross section as well as accompanying activities in the small-angle region
show the direct evidence for the resolved photon processes. We also present
some properties of the two-jet sample with the emphasis on their correlation
with the remnant-jet activity.


title:
Study of ttbar Production in ppbar Collisions Using Total Transverse
  Energy

abstract:
  We analyze a sample of W + jet events collected with the Collider Detector at
Fermilab (CDF) in ppbar collisions at sqrt(s) = 1.8 TeV to study ttbar
production. We employ a simple kinematical variable "H", defined as the scalar
sum of the transverse energies of the lepton, neutrino and jets. For events
with a W boson and four or more jets, the shape of the "H" distribution
deviates by 3.8 standard deviations from that expected from known backgrounds
to ttbar production. However this distribution agrees well with a linear
combination of background and ttbar events, the agreement being best for a top
mass of 180 GeV/c^2.


title:
Limits on $\nu_\mu(\bar{\nu}_\mu)\to\nu_\tau(\bar{\nu}_\tau)$ and
  $\nu_\mu(\bar{\nu}_\mu)\to\nu_e(\bar{\nu}_e)$ Oscillations from a Precision
  Measurement of Neutrino-Nucleon Neutral Current Interactions

abstract:
  We present limits on $\nu_\mu(\bar{\nu}_\mu)\to\nu_\tau(\bar{\nu}_\tau)$ and
$\nu_\mu(\bar{\nu}_\mu)\to\nu_e(\bar{\nu}_e)$ oscillations based on a study of
inclusive $\nu N$ interactions performed using the CCFR massive coarse grained
detector in the FNAL Tevatron Quadrupole Triplet neutrino beam. The sensitivity
to oscillations is from the difference in the longitudinal energy deposition
pattern of $\nu_\mu N$ versus $\nu_\tau N$ or $\nu_e N$ charged current
interactions. The $\nu_\mu$ energies ranged from 30 to 500 GeV with a mean of
140 GeV. The minimum and maximum $\nu_\mu$ flight lengths are 0.9 km and 1.4 km
respectively. For $\nu_\mu\to\nu_\tau$ oscillations, the lowest 90% confidence
upper limit in $\sin^22\alpha$ of $2.7\times 10^{-3}$ is obtained at $\Delta
m^2\sim50$~eV$^2$. This result is the most stringent limit to date for
$25<\Delta m^2<90$ eV$^2$. For $\nu_\mu\to\nu_e$ oscillations, the lowest 90%
confidence upper limit in $\sin^22\alpha$ of $1.9\times 10^{-3}$ is obtained at
$\Delta m^2\sim350$~eV$^2$. This result is the most stringent limit to date for
$250<\Delta m^2<450$ eV$^2$, and also excludes at 90% confidence much of the
high $\Delta m^2$ region favored by the recent LSND observation.


title:
Search for New Particles Decaying to Dijets, Bottom Quarks, and Top
  Quarks at CDF

abstract:
  We present three searches for new particles at CDF. First, using 70 pb^-1 of
data we search the dijet mass spectrum for resonances. There is an upward
fluctuation near 550 GeV (2.6 sigma) with an angular distribution that is
adequately described by either QCD alone or QCD plus 5% signal. There is
insufficient evidence to claim a signal, but we set the most stringent mass
limits on the hadronic decays of axigluons, excited quarks, technirhos, W', Z',
and E6 diquarks. Second, using 19 pb^-1 of data we search the b-tagged dijet
mass spectrum for b anti-b resonances. Again, an upward fluctuation near 600
GeV (2 sigma) is not significant enough to claim a signal, so we set the first
mass limits on topcolor bosons. Finally, using 67 pb^-1 of data we search the
top quark sample for t anti-t resonances like a topcolor Z'. Other than an
insignificant shoulder of 6 events on a background of 2.4 in the mass region
475-550 GeV, there is no evidence for new particle production. Mass limits,
currently in progress, should be sensitive to a topcolor Z' near 600 GeV. In
all three searches there is insufficient evidence to claim new particle
production, yet there is an exciting possibility that the upward fluctuations
are the first signs of new physics beyond the standard model.


title:
Diffractive Hard Photoproduction at HERA and Evidence for the Gluon
  Content of the Pomeron

abstract:
  Inclusive jet cross sections for events with a large rapidity gap with
respect to the proton direction from the reaction $ep \rightarrow jet \; + \;
X$ with quasi-real photons have been measured with the ZEUS detector. The cross
sections refer to jets with transverse energies $E_T^{jet}>8$~GeV. The data
show the characteristics of a diffractive process mediated by pomeron exchange.
Assuming that the events are due to the exchange of a pomeron with partonic
structure, the quark and gluon content of the pomeron is probed at a scale
$\sim (E_T^{jet})^2$. A comparison of the measurements with model predictions
based on QCD plus Regge phenomenology requires a contribution of partons with a
hard momentum density in the pomeron. A combined analysis of the jet cross
sections and recent ZEUS measurements of the diffractive structure function in
deep inelastic scattering gives the first experimental evidence for the gluon
content of the pomeron in diffractive hard scattering processes. The data
indicate that between 30\% and 80\% of the momentum of the pomeron carried by
partons is due to hard gluons.


title:
A Measurement of $\alpha_s(M_Z^2)$ from the Gross Llewellyn Smith Sum
  Rule

abstract:
  The Gross Llewellyn Smith sum rule has been measured at different values of
four-momentum transfer squared ($Q^{2}$) by combining the precise CCFR neutrino
data with data from other deep-inelastic scattering experiments at lower values
of $Q^{2}$. A comparison with the ${\cal O}(\alpha^{3}_{s})$ predictions of
perturbative QCD yields a determination of $\alpha_{s}$ and its dependence on
$Q^{2}$ in the range $1\,GeV^2 < Q^{2} < 20 \,GeV^{2}$. Low \qsq\ tests have
greater sensitivity to \alfs(\mztwo) than high \qsq\ tests, since at low $Q^2$,
$\alpha_s$ is large and changing rapidly.


title:
Measurement of the Proton Structure Function $F_2$ and the Extraction of
  the Gluon Density at Small $x$

abstract:
  In the following article we describe our measurement of the proton structure
function $F_2$ and of the gluon momentum density $xg$ in $ep$ collisions with
the ZEUS detector at HERA in 1993. The results for $F_2$ confirm our
measurement from the previous year but with much higher statistics and show a
strong rise towards small $x$. The gluon momentum density $xg$ is measured for
the first time in a range from $ 4 \cdot 10^{-4} < x < 10^{-2}$ at a value of
$Q^2 = 20$~GeV$^2$.


title:
Transverse Energy and Forward Jet Production in the Low $x$ Regime at
  HERA

abstract:
  The production of transverse energy in deep inelastic scattering is measured
as a function of the kinematic variables $x$ and $Q^2$ using the H1 detector at
the ep collider HERA. The results are compared to the different predictions
based upon two alternative QCD evolution equations, namely the
Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and the
Balitsky-Fadin-Kuraev-Lipatov (BFKL) equations. In a pseudorapidity interval
which is central in the hadronic centre of mass system between the current and
the proton remnant fragmentation region the produced transverse energy
increases with decreasing $x$ for constant $Q^2$. Such a behaviour can be
explained with a QCD calculation based upon the BFKL ansatz. The rate of
forward jets, proposed as a signature for BFKL dynamics, has been measured.


title: A new algorithm for automatic photopeak searches

abstract:
  A new, "quantum mechanical" algorithm is proposed for automatic photopeak
location in gamma-ray spectra from semiconductor and scintillator detectors.


title: Proton-Antiproton Collider Physics

abstract:
  Summary of the 10th Topical Workshop on Proton-Antiproton Collider Physics,
Fermilab, May 9-13, 1995.


title: Are Antiprotons Forever?

abstract:
  Up to one million antiprotons from a single LEAR spill have been captured in
a large Penning trap. Surprisingly, when the antiprotons are cooled to energies
significantly below 1 eV, the annihilation rate falls below background. Thus,
very long storage times for antiprotons have been demonstrated in the trap,
even at the compromised vacuum conditions imposed by the experimental set up.
The significance for future ultra-low energy experiments, including portable
antiproton traps, is discussed.


title:
Exclusive $\rho^0$ production in deep inelastic electron-proton
  scattering at HERA

abstract:
  The exclusive production of $\rho^0$ mesons in deep inelastic electron-proton
scattering has been studied using the ZEUS detector. Cross sections have been
measured in the range $7 < Q^2 < 25$ GeV$^2$ for $\gamma^*p$ centre of mass
(c.m.) energies from 40 to 130 GeV. The $\gamma^*p \to \rho^0 p$ cross section
exhibits a $Q^{-(4.2 \pm 0.8 ^{+1.4}_{-0.5})}$ dependence and both
longitudinally and transversely polarised $\rho^0$'s are observed. The
$\gamma^*p \to \rho^0 p$ cross section rises strongly with increasing c.m.
energy, when compared with NMC data at lower energy, which cannot be explained
by production through soft pomeron exchange. The data are compared with
perturbative QCD calculations where the rise in the cross section reflects the
increase in the gluon density at low $x$. the gluon density at low $x$.


title:
Second Generation Leptoquark Search in p\bar{p} Collisions at $\sqrt{s}$
  = 1.8 TeV

abstract:
  We report on a search for second generation leptoquarks with the D\O\
detector at the Fermilab Tevatron $p\bar{p}$ collider at $\sqrt{s}$ = 1.8 TeV.
This search is based on 12.7 pb$^{-1}$ of data. Second generation leptoquarks
are assumed to be produced in pairs and to decay into a muon and quark with
branching ratio $\beta$ or to neutrino and quark with branching ratio
$(1-\beta)$. We obtain cross section times branching ratio limits as a function
of leptoquark mass and set a lower limit on the leptoquark mass of 111
GeV/c$^{2}$ for $\beta = 1 $ and 89 GeV/c$^{2}$ for $\beta = 0.5 $ at the 95%\
confidence level.


title:
Search for the Flavor-Changing Neutral-Current Decays $D^+\to \pi^+
  \mu^+ \mu^-$ and $D^+\to \pi^+ e^+ e^-$

abstract:
  We report the results of a search for the flavor-changing neutral-current
decays $D^+\rightarrow \pi^+ \mu^+ \mu^-$ and $D^+\rightarrow \pi^+ e^+ e^-$ in
data from Fermilab charm hadroproduction experiment E791. No signal above
background is found, and we obtain upper limits on branching fractions,
$B(D^+\rightarrow \pi^+ \mu^+ \mu^-) < 1.8 \times 10^{-5}$ and
$B(D^+\rightarrow \pi^+ e^+ e^-) < 6.6 \times 10^{-5}$, at the 90\% confidence
level.


title: Measurement of the Omega_c Lifetime

abstract:
  We present the measurement of the lifetime of the Omega_c we have performed
using three independent data samples from two different decay modes. Using a
Sigma- beam of 340 GeV/c we have obtained clean signals for the Omega_c
decaying into Xi- K- pi+ pi+ and Omega- pi+ pi- pi+, avoiding topological cuts
normally used in charm analysis. The short but measurable lifetime of the
Omega_c is demonstrated by a clear enhancement of the signals at short but
finite decay lengths. Using a continuous maximum likelihood method we
determined the lifetime to be tau(Omega_c) = 55 +13-11(stat) +18-23(syst) fs.
This makes the Omega_c the shortest living weakly decaying particle observed so
far. The short value of the lifetime confirms the predicted pattern of the
charmed baryon lifetimes and demonstrates that the strong interaction plays a
vital role in the lifetimes of charmed hadrons.


title:
A Measurement of the Form Factors of Light Pseudoscalar Mesons at a
  Large Momentum Transfer

abstract:
  Using the CLEO-II detector, we have studied the exclusive two-photon
production of the light pseudoscalar mesons in a single tagged mode. We report
on a preliminary measurement of the $\pi^0$, $\eta$ and $\eta^{\prime}$
electromagnetic form factors in the $Q^2$ region from 2 ${\rm (GeV/c)}^2$ to 20
${\rm (GeV/c)}^2$.}


title:
Measurements of the Two-Photon Widths of the Charmonium States
  ${\eta_c}$, $\chi_{c{\large{0}}}$ and $\chi_{c{\large{2}}}$

abstract:
  Using the CLEO-II detector at the CESR $e^+e^-$ storage ring running at the
center-of-mass energy around 10.6 GeV, we have studied exclusive production of
charmonium states in two-photon collisions. Employing a dataset comprising 3.0
${\rm fb}^{-1}$ we have searched for decays of the $\eta_c$, $\chi_{c0}$ and
$\chi_{c2}$ mesons resulting in four charged hadrons. We report on the
measurements of the cross sections and two-photon widths of these charmonium
states.


title: Search for the Top Quark at D0 using Multivariate Methods

abstract:
  We report on the search for the top quark in proton-antiproton collisions at
the Fermilab Tevatron in the di-lepton and lepton+jets channels using
multivariate methods. An H-matrix analysis of the e-mu data corresponding to an
integrated luminosity of about 13.5 pb-1 yields one event with a likelihood to
be a top event (assuming top mass of 180 GeV/c**2) that is 10 times more than
WW and 18 times more than Z -> tau tau. A neural network analysis of e+jets
channel with about 48 pb-1 of data shows an excess of events in the signal
region and yields a cross-section for top-antitop production of 6.7 +/-
2.3(stat.) pb, assuming a top mass of 200 GeV/c**2. A PDE analysis of e+jets
data gives results consistent with the above.


title:
Measurables of $CP$ Violation in $B_d\to D^0_{CP}K_S$ at a $B$-meson
  Factory

abstract:
  In the context of the standard electroweak model, we emphasize that
$B_d\rightarrow D^0_{CP}K_S$ ($D^0_{CP}$ denotes a $CP$ eigenstate of $D^0$ or
$\bar{D}^0$) can compete with $B_d\rightarrow \pi^+\pi^-$ in studying $CP$
violation and probing the Cabibbo-Kobayashi-Maskawa unitarity triangle. We
discuss the measurables of direct and indirect $CP$ asymmetries in $B^0_d$ vs
$\bar{B}^0_d\rightarrow D^0_{CP}K_S$ under the circumstance of an asymmetric
$B$-meson factory running on the $\Upsilon(4S)$ resonance, and show that both
the weak and strong phases are experimentally determinable even in the presence
of unknown final-state interactions.


title: Production of Eta-Mesons in 200 AGeV/c S+S and S+Au Reactions

abstract:
  Minimum Bias production cross sections of $\eta$ mesons have been measured in
200 AGeV/c S+Au and S+S collisions at the CERN SPS by reconstructing the $\eta
\to \gamma\gamma$ decay. The measurements have been made over the rapidity
range $2.1 \leq y \leq 2.9$ using the leadglass spectrometer of WA80. Within
the statistical and systematical uncertainties the spectral shapes of $\pi^0$
and $\eta$ mesons yields are identical when their invariant differential cross
section is plotted as a function of the transverse mass. The relative
normalization of the $\eta$ to $\pi^0$ transverse mass spectra is found to be
$0.53 \pm 0.07$ for S+Au and $0.43 \pm 0.15$ for S+S reactions. Extrapolation
to full phase space leads to an integrated cross section ratio of $\eta$ to
$\pi^0$ mesons of $0.147 \pm 0.017 {\rm (stat.)} \pm 0.015 {\rm (syst.)}$, and
$0.120 \pm 0.034 {\rm (stat.)} \pm 0.022 {\rm (syst.)}$ for S+Au and S+S
collisions, respectively.


title:
Measurements of $\alpha_s$ From Scaling Violations and From $R_\tau$ at
  LEP

abstract:
  The results of two methods to extract the strong coupling constant,
$\alpha_s$, are reviewed for the LEP experiments. In the first, scaling
violations in the scaled momentum distributions of charged particles at LEP and
at lower energy experiments are employed. In the second, QCD corrections to
$R_\tau$, the ratio of hadronic to leptonic decay rates of the tau lepton,
determine $\alpha_s$ and, using moments of the invariant mass distribution in
hadronic tau decays, the non-perturbative corrections to $R_\tau$.


title: Measurement of Elastic $\rho^0$ Photoproduction at HERA

abstract:
  Elastic $\rho^0$ photoproduction has been measured using the ZEUS detector at
HERA. Untagged photoproduction events from $ep$ interactions were used to
measure the reaction $\gamma p \rightarrow \rho^0 p$ ($\rho^0 \rightarrow \pi^+
\pi^-$) at photon-proton centre-of-mass energies between 60 and 80~GeV and
$|t|<0.5$~GeV$^2$, where $t$ is the square of the four-momentum transferred at
the proton vertex. The differential cross section $d\sigma/dM_{\pi\pi}$, where
$M_{\pi\pi}$ is the invariant mass of the two pions, and the integrated cross
section, $\sigma_{\gamma p\rightarrow \rho^0 p}$, are presented; the latter was
measured to be $14.7\pm 0.4~(\mbox{stat.})~\pm2.4~(\mbox{syst.})~\mu\mbox{b}$.
The differential cross section $d\sigma/dt$ has an approximately exponential
shape; a fit of the type $A^{\prime}_{t} \exp{(-b^{\prime}_{t}|t| +
c^{\prime}_{t} t^2)}$ yields a $t$-slope $b^{\prime}_{t}=
9.9~\pm~1.2~(\mbox{stat.})~\pm 1.4~(\mbox{syst.})~\mu\mbox{b}$. The results,
when compared to low energy data, show a weak energy dependence of both
$\sigma_{\gamma p\rightarrow \rho^0 p}$ and of the $t$-slope. The $\rho^0$ is
produced predominantly with transverse polarisation, demonstrating that
$s$-channel helicity conservation holds at these energies.


title:
Measurements of the W and Z Inclusive Cross Sections and Determination
  of the W Decay Width

abstract:
  Recent results on the production of $W$ and $Z$ gauge bosons in $p\bar{p}$
collisions at $\sqrt{s}=1.8$~TeV at the Fermilab Tevatron Collider from the \D0
and CDF experiments are reviewed. Measurements of the inclusive cross sections
times leptonic branching ratios in both the electron and muon decay channels
are summarized and compared to QCD predictions. Using the ratio $R = {\sigma_W
\cdot B(W\rightarrow l\nu)}/ {\sigma_Z \cdot B(Z\rightarrow ll)}$ and assuming
standard model couplings, an indirect determination of the W decay width is
obtained. By comparing this measured value with the predicted value for the $W$
width, a limit on the deviation from the standard model is obtained.


title:
An Investigation into the Radiation Damage of the Silicon Detectors of
  the H1-PLUG Calorimeter within the HERA environment

abstract:
  The silicon detectors used in the H1-PLUG calorimeter have shown increasing
aging effects during the '94 run period of the electron proton storage ring
HERA. These effects were particularly manifest as degradation of the signal to
noise level and the calibration stability. The reasons for this behaviour have
been found to be correlated with radiation damage to the silicon oxide
passivation edges of the detectors in strong and fluctuating increases of the
leakage currents and in severe changes of the flat band voltages. Depletion
voltages however are found to be stable and therefore bulk damage of the
silicon can be excluded. A comparison with measurements made by
thermoluminescence dosimeters as well as related laboratory experiments suggest
that the aging is due to very low energetic electrons and photons.


title: Search for Anomalous $WW$ and $WZ$ production at {D\O}

abstract:
  We present a preliminary result from a search for anomalous $WW$ and $WZ$
production in $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV using
$p\bar{p}\rightarrow e\nu jj$ events observed during the 1992--1993 run of the
Fermilab Tevatron collider. A fit to the $p_T$ spectrum of $W(e\nu)$ yields
direct limits on the CP--conserving anomalous $WW\gamma$ and $WWZ$ coupling
parameters of $-0.89<\Delta\kappa<1.07~~(\lambda=0)$ and
$-0.66<\lambda<0.67~~(\Delta\kappa=0)$ at the $95\ \%$ confidence level,
assuming that the $WWZ$ coupling parameters are equal to the $WW\gamma$
coupling parameters, and a form factor scale $\Lambda=1.5$~TeV.


title: Observation of the Isospin-Violating Decay $D_s^{*+}\to D_s^+\pi^0$

abstract:
  Using data collected with the CLEO~II detector, we have observed the
isospin-violating decay $D_s^{*+}\to D_s^+\pi^0$. The decay rate for this mode,
relative to the dominant radiative decay, is found to be $\Gamma(D_s^{*+}\to
D_s^+\pi^0)/\Gamma(D_s^{*+}\to D_s^+\gamma)= 0.062^{+0.020}_{-0.018}\pm0.022$.


title: Tests of QCD in W and Z Production at Tevatron

abstract:
  We present measurements of the production cross sections times leptonic
branching fractions and the transverse momentum distributions of $W$ and $Z$
bosons in $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV using data collected with
the D{\O}detector at the Fermilab Tevatron $p\bar{p}$ collider. A preliminary
measurement of the $W$ charge asymmetry is also presented.


title: Search for Magnetic Monopoles Trapped in Matter

abstract:
  There have been many searches for magnetic monopoles in flight, but few for
monopoles in matter. We have searched for magnetic monopoles in meteorites,
schists, ferromanganese nodules, iron ores and other materials. The detector
was a superconducting induction coil connected to a SQUID (Superconducting
Quantum Interference Device) with a room temperature bore 15 cm in diameter. We
tested a total of more than 331 kg of material including 112 kg of meteorites.
We found no monopole and conclude the overall monopole/nucleon ratio in the
samples is $<1.2 \times 10^{-29}$ with a 90\% confidence level.


title: Search for Exclusive Charmless Hadronic B Decays

abstract:
  We have searched for two-body charmless hadronic decays of $B$ mesons. Final
states include $\pi\pi$, $K \pi$, and $KK$ with both charged and neutral kaons
and pions; $\pi\rho$, $K \rho$, and $K^*\pi$; and $K\phi$, $ K^*\phi$, and
$\phi\phi$. The data used in this analysis consist of 2.6~million
$B\bar{B}$~pairs produced at the $\Upsilon(4S)$ taken with the CLEO-II detector
at the Cornell Electron Storage Ring (CESR). We measure the branching fraction
of the sum of $B^0 \rightarrow \pi^+\pi^-$ and $B^0 \rightarrow K^+\pi^-$ to be
$(1.8^{+0.6+0.2}_{-0.5-0.3}\pm0.2) \times 10^{-5}$. In addition, we place upper
limits on individual branching fractions in the range from $10^{-4}$ to
$10^{-6}$.


title: Observation of the Cabibbo Suppressed Charmed Baryon Decay

abstract:
  We report the observation of the Cabibbo-suppressed decays \lcpkk\ and
\lcpphi\ using data collected with the CLEO II detector at CESR. The latter
mode, observed for the first time with significant statistics, is of interest
as a test of color-suppression in charm decays. We have determined the
branching ratios for these modes relative to \lcpkpi\ and compared our results
with theory.


title:
Observation of the $\Xi_c^+$ Charmed Baryon Decays to $\Sigma^+
  K^-\pi^+$, $\Sigma^+ \bar{K}^{*0}$, and $\Lambda K^-\pi^+\pi^+$

abstract:
  We have observed two new decay modes of the charmed baryon $\Xi_c^+$ into
$\Sigma^+ K^-\pi^+$ and $\Sigma^+ \bar{K}^{*0}$ using data collected with the
CLEO II detector. We also present the first measurement of the branching
fraction for the previously observed decay mode $\Xi_c^+\to\Lambda
K^-\pi^+\pi^+$. The branching fractions for these three modes relative to
$\Xi_c^+\to\Xi^-\pi^+\pi^+$ are measured to be $1.18 \pm 0.26 \pm 0.17$, $0.92
\pm 0.27 \pm 0.14$, and $0.58 \pm 0.16 \pm 0.07$, respectively.


title:
The Cherenkov Correlated Timing Detector: Beam Test Results from Quartz
  and Acrylic Bars

abstract:
  Several prototypes of a Cherenkov Correlated Timing (CCT) Detector have been
tested at the KEK-PS test beam line. We describe the results for Cherenkov
light yields and timing characteristics from quartz and acrylic bar prototypes.
A Cherenkov angle resolution is found to be 15 mrad at a propagation distance
of 100 cm with a 2 cm thick quartz bar prototype.


title:
The Cherenkov Correlated Timing Detector: Materials, Geometry and Timing
  Constraints

abstract:
  The key parameters of Cherenkov Correlated Timing (CCT) detectors are
discussed. Measurements of radiator geometry, optical properties of radiator
and coupling materials, and photon detector timing performance are presented.


title:
Measurements of the Ratios ${\cal B}(D_s^+\to \eta\ell^+\nu)/{\cal
  B}(D_s^+\to \phi\ell^+\nu)$ and ${\cal B}(D_s^+\to \eta'\ell^+\nu)/{\cal
  B}(D_s^+\to \phi\ell^+\nu)$

abstract:
  Using the CLEO~II detector we measure ${\cal B}(D_s^+\to \eta e^+\nu)/{\cal
B}(D_s^+\to \phi e^+\nu) =1.24\pm0.12\pm0.15$, ${\cal B}(D_s^+\to \eta'
e^+\nu)/{\cal B}(D_s^+\to \phi e^+\nu) =0.43\pm0.11\pm0.07$ and ${\cal
B}(D_s^+\to \eta' e^+\nu)/{\cal B}(D_s^+\to \eta e^+\nu) =0.35\pm0.09\pm0.07$.
We find the vector to pseudoscalar ratio, ${\cal B}(D_s^+\to \phi e^+\nu)/{\cal
B}(D_s^+\to (\eta+\eta') e^+\nu) =0.60\pm0.06\pm0.06$, which is similar to the
ratio found in non strange $D$ decays.


title: Observation of a Narrow State Decaying into $\Xi_c^+\pi^-$

abstract:
  Using data recorded by the CLEO-II detector at CESR, we report the first
observation of a narrow state decaying into $\Xi_c^+\pi^-$. The state has mass
difference $M(\Xi_c^+\pi^-)-M(\Xi_c^+)$ of $178.2\pm0.5\pm1.0$ $\rm{MeV/c^2}$,
and a width of $<5.5$ $\rm{MeV/c^2}$ (90\% confidence level limit). The most
likely explanation of this new state is that it is the $J=\32$ spin excitation
of the $\Xi_c^0$ charmed baryon.


title: Detection of the RF Pulse Associated With Cosmic Ray Air Showers

abstract:
  A project to detect the radio-frequency pulse associated with extensive air
showers of cosmic rays is described briefly. Prototype work is being performed
at the CASA/MIA array in Utah, with the intention of designing equipment that
can be used in conjunction with the Auger Giant Array proposal.


title: Preliminary Results For Exclusive $b\to u\ell\nu$ Decays From CLEO

abstract:
  A preliminary analysis of exclusive $\btou$ decays to the final states
$\pi^\pm\ell\nu$, $\pi^0\ell\nu$, $\rho^\pm\ell\nu$, $\rho^0\ell\nu$\ and
$\omega\ell\nu$ based on $2.2\e{6}$ $\bbar$ decays collected at CLEO is
presented. We have measured the first exclusive $\btou$ branching fraction
$\bbpi=[1.19\pm0.41\pm0.21\pm0.19]\e{-4}$
($[1.70\pm0.51\pm0.31\pm0.27]\e{-4}$), with the ISGW (WSB) model used for
efficiency determination. A 90\% C.L. upper limit on $\bbrho$ similar to the
previous CLEO limit is obtained. The ratio $\gamrho/\gampi<3.4$ at the 90\%
confidence level for both the ISGW and WSB models. This ratio provides some
discrimination between form factor models.


title:
Comparison of Deep Inelastic Scattering with Photoproduction
  Interactions at HERA

abstract:
  Photon-proton ($\gamma p$) interactions with~$Q^2<10^{-2}$~GeV$^2$ and
deep-inelastic scattering ($\gamma^* p$) interactions with photon virtualities
$Q^2>5$~GeV$^2$ are studied at the high energy electron-proton collider HERA.
The transverse energy flow and relative rates of large rapidity gap events are
compared in the two event samples. The observed similarity between $\gamma p$
and $\gamma^* p$ interactions can be understood in a picture where the photon
develops as a hadronic object. The transverse energy density measured in the
central region of the collision, at $\eta^*=0$ in the $\gamma^* p$ centre of
mass frame, is compared with data from hadron-hadron interactions as function
of the CMS energy of the collision.


title: Hadronic Final States in Deeply Inelastic Scattering

abstract:
  Results on hadronic final states in deeply inelastic scattering are reviewed.
They comprise jet production and its interpretation in perturbative QCD,
signatures to distinguish conventional QCD dynamics from possible new features
of QCD at small $x$, and measurements of inclusive charged particle production.
Theoretical developments such as color dipole emission and instanton induced
final states are reported on.


title: Physics of An Ultrahigh-Statistics Charm Experiment

abstract:
  We review the physics goals of an ultrahigh-statistics charm experiment and
place them in the broader context of the community's efforts to study the
Standard Model and to search for physics beyond the Standard Model, and we
point out some of the experimental difficulties which must be overcome if these
goals are to be met.


title:
Direct and resolved photoproduction at HERA with virtual and quasi-real
  photons

abstract:
  Preliminary results are presented from a study of dijet photoproduction in ep
collisions with both virtual and quasi-real photons at the ZEUS detector.
Samples of events with photons of virtuality $P^2$ in the ranges $0.1 < P^2 <
0.55$ GeV$^2$ and $P^2 < 0.02$ GeV$^2$ having two jets of $E_T^{jet} > 4$ GeV
in the final state have been obtained. For both quasi-real and virtual photons,
uncorrected distributions of the quantity $x_{\gamma}^{obs}$, the fraction of
the photon momentum manifest in the two highest $E_T$ jets, are presented.
These distributions are sensitive to the relative contributions of the direct
and resolved processes. Resolved photon processes are evident in both data
sets, with an apparent decrease in the relative contribution from resolved
processes as photon virtuality increases.


title:
Measurement of correlated $\mu - {overline b}$ jet cross sections in $p
  {\bar p}$ collisions at $\sqrt{s}=1.8$ TeV

abstract:
  We report on measurements of differential $\mu - {\bar b}$ cross sections,
where the muon is from a semi-leptonic $b$ decay and the ${\bar b}$ is
identified using precision track reconstruction in jets. The semi-differential
correlated cross sections, d$\sigma$/d$\Et^{{\bar b}}$, d$\sigma$/d$\pt^{{\bar
b}}$, and d$\sigma$/d$\delta\phi(\mu - {\bar b})$ for $\pt^{\mu}>$~9 GeV/c,
$|\eta^{\mu}|<$~0.6, $\Et^{{\bar b}}>$~10 GeV, $|\eta^{{\bar b}}|<$~1.5, are
presented and compared to next-to-leading order QCD calculations.


title: High-Impact Charm Physics at the Turn of the Millennium

abstract:
  I review the sensitivities achieved by and projected for fixed-target charm
experiments in CP violation, flavor-changing neutral-current and
lepton-number-violating decays, and mixing, and I describe the Charm2000
experiment intended to run at Fermilab in the Year ~2000. If approved,
Charm2000 will in many of these areas exceed the sensitivities projected for a
Tau/Charm Factory, but the Tau/Charm Factory retains certain qualitative
advantages.


title:
Measurement of the Total Photon Proton Cross Section and its
  Decomposition at 200~GeV Centre of Mass Energy

abstract:
  We present a new measurement of the total photoproduction cross section
performed with the H1 detector at HERA. For an average centre of mass energy of
200~GeV a value of $\sigma_{tot}^{\gamma{p}}= 165\pm2\pm11\mu$b has been
obtained. A detailed analysis of the data in adequate kinematic regions enabled
a decomposition of the total cross section in its elastic, single diffractive
dissociation and remaining non-diffractive parts, based on safe assumptions on
the double diffractive dissociation contribution.


title: CLEO III, A Dectector To Measure Rare $B$ Decays and CP Violation

abstract:
  The symmetric $e^+e^-$ collider CESR is undergoing a series of upgrades
allowing for luminosities in excess of $2\times 10^{33}$cm$^{-2}$s$^{-1}$. The
most important goals of the upgrade are precision measurement of standard model
parameters $V_{cb}$, $V_{ub}$, $V_{td}/V_{ts}$, $f_{D_s}$, and searching for CP
violation and standard model violations in rare $B$ decays. A new detector
upgrade, called CLEO III, has started which includes a new silicon-wire drift
chamber tracking system and a Ring Imaging Cherenkov Detector, RICH, using a
LiF radiator and CH$_4$-TEA gas based photon detector.


title: The Ring Imaging Detector for Cleo III

abstract:
  The CLEO detector will undergo major improvements in conjunction with a high
luminosity upgrade of the CESR electron positron collider, that should increase
the luminosity of this machine by a factor of 10. The most innovative feature
of the planned CLEO detector is the addition of a state of the art particle
identification system, based on a proximity focused Ring Imaging Cherenkov
detector. The goal is to achieve good hadron identification at all the momenta
relevant to the study of decays of B mesons produced at the upsilon(4S)
resonance. This detector design will be discussed, including details of the
mechanical design and the readout electronics. The performance of a prototype
module will be described.


title: Hard Photoproduction by Colour Singlet Exchange at HERA

abstract:
  A search for photoproduction events which contain a rapidity gap between the
two highest transverse energy jets has been conducted at HERA using the ZEUS
detector. The jets have transverse energies greater than 6~GeV, and are
separated by pseudorapidity intervals of up to four units. The fraction of
events containing a gap is measured as a function of the gap-width. It is
expected that this gap-fraction will fall exponentially with the gap-width,
until the dominant gap-production mechanism becomes colour singlet exchange, at
which point it will plateau. An indication of a plateau in the measured
gap-fraction has been found, at a higher level than that expected from
electroweak exchange.


title:
Studies of Topological Distributions of the Three- and Four-Jet Events
  in $\pp$ Collisions at $\sqrt{s}=1800$ GeV with the D{\O}Detector

abstract:
  The global topologies of inclusive three-- and four--jet events produced in
$\pp$ interactions are described. The three-- and four--jet events are selected
from data recorded by the D{\O}detector at the Tevatron Collider operating at a
center--of--mass energy of $\sqrt{s} = 1800$ GeV. The measured, normalized
distributions of various topological variables are compared with parton--level
predictions of tree--level QCD calculations. The parton--level QCD calculations
are found to be in good agreement with the data. The studies also show that the
topological distributions of the different subprocesses involving different
numbers of quarks are very similar and reproduce the measured distributions
well. The parton shower Monte Carlo generators provide a less satisfactory
description of the topologies of the three-- and four--jet events.


title: $B_s$ Mixing via $\psi K^*$

abstract:
  The decay mode $B_s\to\psi \overline{K}^*$ is suggested as a very good way to
measure the $B_s$ mixing parameter $x_s$. These decays can be gathered using a
$\psi\to\ell^+\ell^-$ trigger. This final state has a well resolved four track
decay vertex, useful for good time resolution and background rejection.


title: The SMC Experiment: New Data on the Deuteron from the 1994 Run

abstract:
  An overview of the SMC data taking and the polarized deep inelastic
scattering experiment is given. The new data on the deuteron extend the
kinematic range and have considerably reduced statistical and systematic
errors. The evaluation of the first moment of the spin dependent structure
function is presented and the result for the Bjorken sum rule from SMC data
alone is given. The spin contribution of the quarks to the spin of the nucleon
is obtained with information from weak decays of baryons. In a new polarized
semi-inclusive analysis the asymmetry of the difference between the number of
positive and negative charged hadrons was studied. Preliminary results are
shown.


title: GaAs Microstrip Testbeam Results

abstract:
  A gallium arsenide detector was tested with a beam of 70GeV pions at the {\sf
SPS} at CERN. The detector utilises a novel biasing scheme which has been shown
to behave as expected. The detector has a pitch of 50$\mu$m and therefore an
expected resolution of 14.5$\mu$m. The measured resolution was approximately
14$\mu$m. By using a non-linear charge division algorithm this can be increased
to $\approx$ 12$\mu$m. Noise was the limiting factor to the resolution. This
was 2000e$^-$ as opposed to the expected 360e$^-$. This noise is also thought
to have reduced the detection efficiency of the detector. The source of the
excess noise is currently being investigated.


title: Fixed-Target CP-Violation Experiments at Fermilab

abstract:
  Studies of CP violation, for 30 years focused primarily on the neutral K
meson, are on the threshold of a new era as experiments approach Standard-Model
sensitivities in decays of beauty, charm, and hyperons. The array of
heavy-quark experiments approved and planned at Fermilab may lead to a
significant breakthrough in the next five to ten years.


title:
Measurement of $\sigma \cdot B (W \to e \nu)$ and $\sigma \cdot B(Z^0
  \to e^+e^-)$ in $p {\bar p}$ collisions at $\sqrt{s}=1.8$ TeV

abstract:
  We present a measurement of $\sigma \cdot B(W \to e \nu)$ and $\sigma \cdot
B(Z^0 \to e^+e^-)$ in proton - antiproton collisions at $\sqrt{s} =1.8$ TeV
using a significantly improved understanding of the integrated luminosity. The
data represent an integrated luminosity of 19.7 pb$^{-1}$ from the 1992-1993
run with the Collider Detector at Fermilab (CDF). We find $\sigma \cdot B(W \to
e \nu) = 2.49 \pm 0.12$~nb and $\sigma \cdot B(Z^0 \to e^+e^-) = 0.231 \pm
0.012$~nb.


title:
Model of charge transport in Semi-Insulating Undoped GaAs microstrip
  detectors

abstract:
  In this paper we present a method for simulating the response of microstrip
detectors to minimum ionizing particles, making use of a program for field
calculation, a program for carrier drift and SPICE for circuit response. A
knowledge of the electric field is essential for any further improvement of the
program. A simple model involving EL2 levels in the metastable state is
proposed to explain some measurements of electric field.


title: Noise Spectra of SIU-GaAs Pad Detectors With Guard Rings

abstract:
  This paper presents current noise characterization of circular pad Schottky
barrier diodes with guard rings. The diodes were fabricated from undopped
semi-insulating GaAs, SIU-GaAs, at the University of Glasgow. Current noise
spectra were obtained for the detectors for two pad sizes, with reverse bias
applied. Three measurements were also made on one of the detectors under
forward bias. The noise spectra show an excess noise component, with a low
frequency corner at less than 1kHz, and a flat region at higher frequencies.
The magnitude of the white noise is approximately half that expected from shot
noise theory for the given leakage currents. A fall in the magnitude of the
noise was observed at 20kHz which is attributed to the dielectric relaxation
time of the material.


title:
Jet Production via Strongly-Interacting Color-Singlet Exchange in
  $p\bar{p}$ Collisions

abstract:
  A study of the particle multiplicity between jets with large rapidity
separation has been performed using the D{\O}detector at the Fermilab Tevatron
$p\bar{p}$ Collider operating at $\sqrt{s}=1.8$ TeV. A significant excess of
low-multiplicity events is observed above the expectation for color-exchange
processes. The measured fractional excess is $1.07 \pm 0.10({\rm stat})^{+
0.25}_{- 0.13}({\rm syst})%$, which is consistent with a strongly-interacting
color-singlet (colorless) exchange process and cannot be explained by
electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on
the fraction of dijet events with color-singlet exchange, independent of the
rapidity gap survival probability.


title:
Large enhancement of deuteron polarization with frequency modulated
  microwaves

abstract:
  We report a large enhancement of 1.7 in deuteron polarization up to values of
0.6 due to frequency modulation of the polarizing microwaves in a two liters
polarized target using the method of dynamic nuclear polarization. This target
was used during a deep inelastic polarized muon-deuteron scattering experiment
at CERN. Measurements of the electron paramagnetic resonance absorption spectra
show that frequency modulation gives rise to additional microwave absorption in
the spectral wings. Although these results are not understood theoretically,
they may provide a useful testing ground for the deeper understanding of
dynamic nuclear polarization.


title:
Measurement of $\alpha_S$ from Jet Rates in Deep Inelastic Scattering at
  HERA

abstract:
  Jet production in deep inelastic scattering for $120<Q^2<3600$~GeV$^2$ has
been studied using data from an integrated luminosity of 3.2~pb$^{-1}$
collected with the ZEUS detector at HERA. Jets are identified with the JADE
algorithm. A cut on the angular distribution of parton emission in the
$\gamma^*$-parton centre-of-mass system minimises the experimental and
theoretical uncertainties in the determination of the jet rates. The jet rates,
when compared to ${\cal O}$($\alpha_{s}$^2$) perturbative QCD calculations,
allow a precise determination of $\alpha_{s}(Q)$ in three $Q^2$-intervals. The
values are consistent with a running of $\alpha_{s}(Q)$, as expected from QCD.
Extrapolating to $Q=M_{Z^0}$ yields $\alpha_{s}(M_{Z^0}) =
0.117~\pm~0.005~(stat)~^{+0.004}_{-0.005}~(syst_{exp})~
~{\pm~0.007}~(syst_{theory})$.


title:
Production of Charm, Charmonium, and Beauty in 800$\,$GeV Proton-Nucleon
  Collisions

abstract:
  Some recent results from the Fermilab fixed-target experiment E789 on
production of charm, charmonium, and beauty are summarized and compared to
model predictions. The data indicate that heavy-quark and quarkonium production
are not yet entirely understood. The largest discrepancy concerns the rate of
$\psi^\prime$ production, which is a factor $\approx$25 above expectations.


title: The ARGUS Vertex Trigger

abstract:
  A fast second level trigger has been developed for the ARGUS experiment which
recognizes tracks originating from the interaction region. The processor
compares the hits in the ARGUS Micro Vertex Drift Chamber to 245760 masks
stored in random access memories. The masks which are fully defined in three
dimensions are able to reject tracks originating in the wall of the narrow
beampipe of 10.5\,mm radius.


title: Search for Exotic Mesons in pi- P Interactions at 18 GeV/c

abstract:
  The recent search for non $q \bar{q}$ mesons in $\pi^{-}p$ interactions at
Brookhaven National Laboratory is summarized. Many final states such as $\eta
\pi$, $\eta' \pi^{-}$, $a_{0} \pi$, $f_{1} \pi$, $a_{2} \pi$, $b_{1} \pi$,
which are favored decay modes of exotics, are under investigation.


title:
First Measurement of the T-odd Correlation between the Z0 Spin and the
  Three-jet Plane Orientation in Polarized Z0 Decays to Three Jets

abstract:
  We present the first measurement of the correlation between the $Z^0$ spin
and the three-jet plane orientation in polarized $Z^0$ decays into three jets
in the SLD experiment at SLAC utilizing a longitudinally polarized electron
beam. The CP-even and T-odd triple product $\vec{S_Z}\cdot(\vec{k_1}\times
\vec{k_2})$ formed from the two fastest jet momenta, $\vec{k_1}$ and
$\vec{k_2}$, and the $Z^0$ polarization vector $\vec{S_Z}$, is sensitive to
physics beyond the Standard Model. We measure the expectation value of this
quantity to be consistent with zero and set 95\% C.L. limits of $-0.022 < \beta
< 0.039$ on the correlation between the $Z^0$-spin and the three-jet plane
orientation.


title: Search for the Decay $K^+ \to \pi^+ \nu \overline{\nu}$

abstract:
  An upper limit on the branching ratio for the decay $K^+ \! \rightarrow \!
\pi^+ \nu \overline{\nu}$ is set at $2.4 \times 10^{-9}$ at the 90\% C.L. using
pions in the kinematic region $214~{\rm MeV}/c < P_\pi < 231~{\rm MeV}/c$. An
upper limit of $5.2 \times 10^{-10}$ is found on the branching ratio for decays
$K^+ \! \rightarrow \! \pi^+ X^0$, where $X^0$ is any massless, weakly
interacting neutral particle. Limits are also set for cases where $M_{X^0}>0$.


title: Searching for Antiproton Decay at the Fermilab Antiproton Accumulator

abstract:
  This paper describes an experimental search for antiproton decay at the
Fermilab Antiproton Accumulator. The E868 (APEX) experimental setup is
described. The APEX data is expected to be sensitive to antiproton decay if the
antiproton lifetimes is less than a few times 100 000 years.


title:
Sensitive germanium thermistors for cryogenic thermal detector of Tokyo
  dark matter search programme

abstract:
  Sensitive n-type and p-type germanium thermistors were fabricated by the melt
doping technique and by the neutron transmutation doping (NTD) technique,
respectively, aiming at a use for the cryogenic thermal detector, or bolometer
of Tokyo dark matter search programme. We report on the measurements of the
sensitivities of these thermistors. In particular, the p-type thermistors are
sensitive enough to scale up our existing prototype LiF bolometer and realize a
multiple array of the bolometers with the total absorber mass of about 1\,kg.


title:
Measurement of the Proton Structure Function ${F_2}$ at low ${x}$ and
  low ${Q^2}$ at HERA

abstract:
  We report on a measurement of the proton structure function $F_2$ in the
range $3.5\times10^{-5}\leq x \leq 4\times10^{-3}$ and 1.5 ${\rm GeV^2} \leq
Q^2 \leq15$ ${\rm GeV^2}$ at the $ep$ collider HERA operating at a
centre-of-mass energy of $\sqrt{s} = 300$ ${\rm GeV}$. The rise of $F_2$ with
decreasing $x$ observed in the previous HERA measurements persists in this
lower $x$ and $Q^2$ range. The $Q^2$ evolution of $F_2$, even at the lowest
$Q^2$ and $x$ measured, is consistent with perturbative QCD.


title: Recent results from TRISTAN

abstract:
  The TRISTAN results from 1994 to 1995 are reviewed in this report. The
physics results dominated the $\gamma \gamma$ physics. Therefore, only these
are selected in this article. We have systematically investigated jet
productions, the $\gamma$-structure function, and charm pair productions in
$\gamma \gamma$ processes. The results, discussions, and future prospects are
presented.


title:
On the Kinematic Reconstruction of $e^+e^-\to W^+W^-\to
  jj\tau\overline{\nu}_\tau$\ Events

abstract:
  We show that the kinematic reconstruction of the $e^+e^-\rightarrow
W^+W^-\rightarrow jj\tau^-\overline{\nu}_\tau$\ events have a one-parameter
ambiguity when reconstructed from the momentum of all measured $W^-$\ decay
products. We propose a {\em hybrid} method of reconstruction of the
$e^+e^-\rightarrow W^+W^-\rightarrow jj\tau^-\overline{\nu}_\tau$\ events. This
is based on the observation that the difference between the $\tau^-$\
production angles and the production angles of the sum of its visible decay
products is small, whilst the $\tau^-$\ energy is poorly reconstructed. This
method consists of taking the $\tau^-$\ production angles from those measured
for the sum of the visible $\tau^-$\ decay products and reconstructing the
$\tau^-$\ energy from energy-momentum conservation constraints. A
reconstruction using this method is found to be well-defined and possess a
unique solution for the $\tau^-$\ momentum range at LEP II and NLC.


title: Rapidity Gaps between Jets in Photoproduction at HERA

abstract:
  Photoproduction events which have two or more jets have been studied in the
$W_{\gamma p}$ range 135~GeV $< W_{\gamma p} <$ 280~GeV with the ZEUS detector
at HERA. A class of events is observed with little hadronic activity between
the jets. The jets are separated by pseudorapidity intervals ($\Delta\eta$) of
up to four units and have transverse energies greater than 6~GeV. A gap is
defined as the absence between the jets of particles with transverse energy
greater than 300~MeV. The fraction of events containing a gap is measured as a
function of $\Delta\eta$. It decreases exponentially as expected for processes
in which colour is exchanged between the jets, up to a value of $\Delta\eta
\sim 3$, then reaches a constant value of about 0.1. The excess above the
exponential fall-off can be interpreted as evidence for hard diffractive
scattering via a strongly interacting colour singlet object.


title:
Test of CPT Symmetry and Quantum Mechanics with Experimental data from
  CPLEAR

abstract:
  We use fits to recent published CPLEAR data on neutral kaon decays to
$\pi^+\pi^-$ and $\pi e\nu$ to constrain the CPT--violation parameters
appearing in a formulation of the neutral kaon system as an open
quantum-mechanical system. The obtained upper limits of the CPT--violation
parameters are approaching the range suggested by certain ideas concerning
quantum gravity.


title: Charged particle production in the fragmentation of quark and gluon jets

abstract:
  Recent results on the total production and angular distribution of charged
particles originated from the fragmentation of quark and gluon jets are
presented. Experimental studies of the multiplicity as a function of the quark
and gluon jet energy, the inter-jet particle flow and the individual
fragmentation fucntions are reviewed and compared to expectations from QCD.


title: A Search for Lambda sub-b in pi^- - A Collisions at 515 GeV/c

abstract:
  An extensive analysis was performed on 8.0 pb-1 of dimuon data produced in
pi- - A collisions at 515 GeV/c to search for Lambda_b events in the decay
channel Lambda_b --> J/psi Lambda^0, with J/psi --> mu^+ mu^- and Lambda^0 -->
p pi^- (and for the conjugate reactions). The data was collected by the
Fermilab fixed target experiments E672 and E706. Several cuts were applied to
the Lambda^0 (and anti-Lambda^0) to make a clean Lambda^0 (and anti-Lambda^0)
data sample. Among the cuts there was a K^0_s mass cut, in which if the
Lambda^0 --> p pi^- (or conjugate reaction) had the mass of the K^0_s under the
hypothesis of both tracks being pi^+ pi^-, the Lambda^0 (or anti-Lambda^0)
candidates were rejected. The results show 2 events in the Lambda_b mass
region. Using the E672/E706 measurement of the bb_bar cross-section, and
considering the 2 Lambda_b event candidates as signal with zero background, an
upper limit to F(Lambda_b) * Br(Lambda_b --> J/psi Lambda^0) was found to be
less than 6.2x10^-2 at 90 % C. L. An upper limit was also calculate without
using the K^0_s mass cut for the Lambda^0 s (and anti-Lambda^0 s), and again,
requiring that the J/psi s originate from secondary vertices, giving that
F(Lambda_b) * Br(Lambda_b --> J/psi Lambda^0) < 3.1x10^-2 at 90 % C. L. and
F(Lambda_b) * Br(Lambda_b --> J/psi Lambda^0) < 3.2x10$^-2 at 90 % C.L.,
respectively.


title:
Estudi de la depend\`encia energ\`etica de les difer\`encies entre jets
  de quarks i gluons utilitzant el detector DELPHI de LEP

abstract:
  Three jet events arising from decays of the $Z^0$ boson, collected by the
DELPHI detector at LEP, were used to measure differences in the properties of
quark and gluon jet fragmentation. Gluon jets were anti-tagged in $b\bar{b}g$
events, by identifiying $b$ quark jets with high purities. Unbiased quark jets
came from events $q\bar{q}\gamma$ with two jets plus one photon. A comparison
of quark and gluon jet properties in different energy ranges was performed for
the first time and within the same detector. The average value of the ratio of
the mean charged multiplicities of gluon and quark jets was measured to be \[
1.232 \pm 0.026 (\mbox{esta.}) \pm 0.018 (\mbox{sist.}) \] where the fraction
of b-quark initiates jets was 11\% and the Durham jet finding algorithm has
been used for the selection of three jet events. In agreement with QCD an
increase of this ratio with energy was observed at a $3\sigma$ level. A further
dependence of this ratio related with the angular acceptance of the algorithm
used to reconstruct jets was also measured. Gluon jets have a broader energy
and particle flow around its jet axis than quark jets of equivalent energy. The
string effect has been observed in fully symmetric three-jet events. The ratio
$R_\gamma$ of the charged particles flow in the $q\bar{q}$ inter-jet region of
the $q\bar{q}g$ and $q\bar{q}\gamma$ samples was measured in agreement with the
perturbative QCD expectation \[
\frac{(N_{qq})_{q\bar{q}g}}{(N_{qq})_{q\bar{q}\gamma}} = 0.058 \pm 0.06
(\mbox{stat.+sist.}) \] The dependence of the mean charged multiplicity on the
hadronic center-of-mass energy was analysed in photon plus $n$-jet events. A
value for


title: Measurement of the Average $B$-Hadron Lifetime in $Z^{0}$ Decays

abstract:
  We report a measurement of the average $B$-hadron lifetime using data
collected with the SLD detector at the SLC in 1993. An inclusive analysis
selected three-dimensional vertices with $B$-hadron lifetime information in a
sample of 50k $Z^{0}$ decays. A lifetime of $1.564\pm0.030\,(\rm stat)\pm
0.037\,(\rm syst)$~ps was extracted from the decay length distribution of these
vertices using a binned maximum-likelihood method.


title: Soft interactions at high energy

abstract:
  Soft interactions are not easily disentangled from hard ones. In an
operational definition of soft and hard processes one finds that at presently
analyzed scales there is an interplay of soft and hard processes. As the scale
increases, so does the amount of hard processes. So far, nothing is as soft nor
as hard as we would like.


title: Production of large rapidity gap events in ep interactions at HERA

abstract:
  This is a short review of the properties of electron proton interactions
characterized by the presence of large rapidity gaps (LRG) in the measured
hadronic final state as obtained by the ZEUS Collaboration at the HERA
Collider. In the deep inelastic neutral current $ep$ interactions, the
factorization properties of the LRG events interpreted as due to the
diffractive dissociation of the virtual photon are compatible with expectations
from the Regge phenomenology of soft interactions. The measurement of deep
inelastic scattering combined with results from photoproduction of high $p_T$
jets are successfully interpreted in terms of a factorizable Pomeron consisting
of quarks and with a substantial contribution of a gluonic component. The first
hints of a more complicated nature of the Pomeron are observed in the deep
inelastic exclusive $\rho^o$ production, where a strong increase of the
production cross section with energy is observed relative to the measurements
of the NMC Collaboration at lower energy.


title:
Estudio del canal electronico de desintegracion del lepton tau en LEP
  con el detector DELPHI

abstract:
  This thesis presents a study of the decays $\tau\rightarrow
e\nu\overline{\nu}$ identified after a selection of $\tau^+\tau^-$ events
produced in $e^+e^-$ collisions at LEP. These collisions, predominantly
mediated by a $Z^0$ boson, offer a good laboratory for the study of weak
current parameters. Moreover, the decays of the tau lepton, which proceed via a
$W$ boson, increase the possibilities of our study. The experimental
observables, which imply an indirect knowledge of the coupling constants,
include the polarization asymmetry and the forward-backward polarization
asymmetry. The branching ratio of the electronic decay of the $\tau$ lepton
($18.24\pm0.28\pm0.32)\%$) derives a measurement of the strong coupling
constant $\alpha_s$ at the scale of the $Z^0$ boson mass
($0.118^{+0.004}_{-0.006}\pm0.006$) and a test of lepton universality in weak
currents ($\frac{g_{\tau}}{g_{\mu}}=1.000\pm0.014$). The spectra of momenta and
electromagnetic energy depositions used as estimates of the energy of the
electron allow to measure the polarization asymmetries
($P_{\tau}=-0.16\pm0.09\pm0.05$ and $A^{FB}_{pol}=-0.19\pm0.09\pm0.01$) giving
subsequent values for the effective $sin^2\theta_W$ ($0.230\pm0.013$ and
$0.218\pm0.015$).


title: A Simple Multiprocessor Management System for Event-Parallel Computing

abstract:
  Offline software using TCP/IP sockets to distribute particle physics events
to multiple UNIX/RISC workstations is described. A modular, building block
approach was taken, which allowed tailoring to solve specific tasks efficiently
and simply as they arose. The modest, initial cost was having to learn about
sockets for interprocess communication. This multiprocessor management software
has been used to control the reconstruction of eight billion raw data events
from Fermilab Experiment E791.


title:
Inclusive Charged Particle Distributions in Deep Inelastic Scattering
  Events at HERA

abstract:
  A measurement of inclusive charged particle distributions in deep inelastic
$ep$ scattering for $\gamma^* p$ centre-of-mass energies $75< W < 175$~GeV and
momentum transfer squared $10< Q^2 < 160$~GeV$^2$ from the ZEUS detector at
HERA is presented. The differential charged particle rates in the $\gamma^* p$
centre-of-mass system as a function of the scaled longitudinal momentum, $x_F$,
and of the transverse momentum, $p_t^*$ and $<\!\!p_t^{*\,2}\!\!>\,\,$ , as a
function of $x_F$, $W$ and $Q^2$ are given. Separate distributions are shown
for events with (LRG) and without (NRG) a rapidity gap with respect to the
proton direction. The data are compared with results from experiments at lower
beam energies, with the naive quark parton model and with parton models
including perturbative QCD corrections. The comparison shows the importance of
the higher order QCD processes. Significant differences of the inclusive
charged particle rates between NRG and LRG events at the same $W$ are observed.
The value of $<\!\!p_t^{*\,2}\!\!>\,\,$ for LRG events with a hadronic mass
$M_X$, which excludes the forward produced baryonic system, is similar to the
$<\!\!p_t^{*\,2}\!\!>\,\,$ value observed in fixed target experiments at $W
\approx M_X$.


title:
The Next Round of Hadronic Generator Tuning Heavily Based on Identified
  Particle Data

abstract:
  Event shape and charged particle inclusive distributions determined from 750
000 hadronic Z events measured with the DELPHI detector at LEP are presented.
The statistical and systematic precision of this data allows for a decisive
confrontation with Monte Carlo models of the hadronization process and a better
understanding of the structure of the Z hadronic final state.
  Improved tunings of the JETSET, ARIADNE and HERWIG parton shower models and
the JETSET matrix element model are obtained by fitting the models to
identified particle distributions from all LEP experiments and the DELPHI data
presented. The description of the data distributions by the models is
critically reviewed with special importance attributed to identified particles.


title: Jets and Energy Flow in Photon-Proton Collisions at HERA

abstract:
  Properties of the hadronic final state in photoproduction events with large
transverse energy are studied at the electron-proton collider HERA.
Distributions of the transverse energy, jets and underlying event energy are
compared to $\overline{p}p$ data and QCD calculations. The comparisons show
that the $\gamma p$ events can be consistently described by QCD models
including -- in addition to the primary hard scattering process -- interactions
between the two beam remnants. The differential jet cross sections
$d\sigma/dE_T^{jet}$ and $d\sigma/d\eta^{jet}$ are measured.


title:
Measurements of the Proton and Deuteron Spin Structure Function g2 and
  Asymmetry A2

abstract:
  We have measured proton and deuteron virtual photon-nucleon asymmetries A2p
and A2d and structure functions g2p and g2d over the range 0.03<x<0.8 and
1.3<Q2<10 (GeV/c)2 by inelastically scattering polarized electrons off
polarized ammonia targets. Results for A2 are significantly smaller than the
positivity limit sqrt(R) for both targets. Within experimental precision, the
g2 data are well-described by the twist-2 contribution g2WW. Twist-3 matrix
elements have been extracted and are compared to theorectical predictions.


title: Measurement of the Inclusive Semi-electronic $D^0$ Branching Fraction

abstract:
  Using the angular correlation between the $\pi^+$ emitted in a $D^{*+}
\rightarrow D^0 \pi^+$ decay and the $e^+$ emitted in the subsequent $D^0
\rightarrow Xe^+\nu$ decay, we have measured the branching fraction for the
inclusive semi-electronic decay of the $D^0$ meson to be: {\cal B}(D^0
\rightarrow X e^+ \nu) = [6.64 \pm 0.18 (stat.) \pm 0.29 (syst.)] \%. The
result is based on 1.7 fb$^{-1}$ of $e^+e^-$ collisions recorded by the CLEO II
detector located at the Cornell Electron Storage Ring (CESR). Combining the
analysis presented in this paper with previous CLEO results we find,
  \frac{{\cal B} (D^0 \rightarrow X e^+ \nu)}
  {{\cal B} (D^0 \rightarrow K^- \pi^+)}
  = 1.684 \pm 0.056 (stat.) \pm 0.093(syst.) and
  \frac{{\cal B}(D\rightarrow K^-e^+\nu)}
  {{\cal B}(D\rightarrow Xe^+\nu)}
  = 0.581 \pm 0.023 (stat.) \pm 0.028(syst.).
  The difference between the inclusive rate and the sum of the measured
exclusive branching fractions (measured at CLEO and other experiments) is $(3.3
\pm 7.2) \%$ of the inclusive rate.


title:
Measurements of the Q2-Dependence of the Proton and Deuteron Spin
  Structure Functions g1p and g1d

abstract:
  The ratio g1/F1 has been measured over the range 0.03<x<0.6 and 0.3<Q2<10
(GeV/c)2 using deep-inelastic scattering of polarized electrons from polarized
protons and deuterons. We find g1/F1 to be consistent with no Q2-dependence at
fixed x in the deep-inelastic region Q^2>1 (GeV/c)2. A trend is observed for
g1/F1 to decrease at lower Q2. Fits to world data with and without a possible
Q2-dependence in g1/F1 are in agreement with the Bjorken sum rule, but Delta_q
is substantially less than the quark-parton model expectation.


title: A Search for Leptoquarks at HERA

abstract:
  A search for leptoquarks at HERA was performed in H1 using 1994 $e^+ p$ data
corresponding to an integrated luminosity of about $3 \pb^{-1}$. Single
leptoquarks were searched for in direct positron-quark fusion processes taking
into account possible decays into lepton-quark pairs of either the first, the
second, or the third generation. No significant deviation from the Standard
Model predictions is found in the various final states studied and mass
dependent exclusion limits are derived on the Yukawa couplings of the
leptoquarks. Compared with earlier results from an analysis of $e^-p$ data,
exclusion limits are considerably improved for leptoquarks which could be
produced via $e^+$-{\it valence~quark} fusion. For leptoquarks with lepton
flavour conserving couplings, masses up to $275 \GeV$ (depending on the
leptoquark type) are excluded for coupling values larger than $\sqrt{ 4 \pi
\alpha_{em}}$. For leptoquarks with lepton flavour violating couplings, masses
up to $225 \GeV$ are excluded for the first time in a direct search for
couplings with leptons of the second or third generation larger than $\sqrt{ 4
\pi \alpha_{em}}$. Fourteen possible combinations of couplings are studied and
stringent exclusion limits comparable or better than any existing direct or
indirect limits are obtained for each leptoquark type.


title: Charm2000: A >10^8-charm experiment for the turn of the millennium

abstract:
  I discuss the physics reach of a fixed-target charm experiment which can
reconstruct >10^8 charm decays, three orders of magnitude beyond the largest
extant sample. Such an experiment may run at Fermilab shortly after the Year
2000. In addition to "programmatic" charm physics such as spectroscopy,
lifetimes, and tests of QCD, this "Charm2000" experiment will have significant
sensitivity to new physics in the areas of CP violation, flavor-changing
neutral-current and lepton-number-violating decays, and mixing, and could
observe direct CP violation in Cabibbo-suppressed decays at the level predicted
by the Standard Model.


title:
Measurement of the Longitudinal Polarization of the HERA Electron Beam
  Using Crystals and the ZEUS Luminosity Monitor

abstract:
  A measurement of the longitudinal polarization of the electron beam at HERA
utilizing coherent interactions of high energy photons in crystals is proposed.
Modification of existing facilities would allow an independent polarization
measurement and a verification of birefringence phenomena in crystals for
20--30~GeV photons. Relevant experimental issues and systematic uncertainties
are also presented.


title:
Search for $\widetilde{W}_1\widetilde{Z}_2$ Production via Trilepton
  Final States in $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV

abstract:
  We have searched for associated production of the lightest chargino,
$\widetilde{W}_1$, and next-to-lightest neutralino, $\widetilde{Z}_2$, of the
Minimal Supersymmetric Standard Model in $p\bar{p}$ collisions at
\mbox{$\sqrt{s}$ = 1.8 TeV} using the \D0 detector at the Fermilab Tevatron
collider. Data corresponding to an integrated luminosity of 12.5$\pm 0.7$ \ipb
were examined for events containing three isolated leptons. No evidence for
$\widetilde{W}_1\widetilde{Z}_2$ pair production was found. Limits on
$\sigma(\widetilde{W}_1\widetilde{Z}_2)$Br$(\widetilde{W}_1\to
l\nu\widetilde{Z}_1)$Br$(\widetilde{Z}_2\to l\bar{l}\widetilde{Z}_1)$ are
presented.


title: CP and Rare Decays

abstract:
  $CP$ violation experiments, new measurements of the parameters of the neutral
\K\ system and searches for rare decays are summarized. Perspectives for the
near future are presented.


title:
UNIBAB, Version 2.2: Monte Carlo Event Generation for Large Angle Bhabha
  Scattering at LEP and SLC Energies

abstract:
  This manual describes version 2.2 of the Monte Carlo event generator UNIBAB
for large angle Bhabha scattering at LEP and SLC. UNIBAB implements higher
order electromagnetic radiative corrections and the effects of soft photon
exponentiation in a photon shower approach. Weak corrections are included
through the use of an electroweak library.


title:
Search for Right-Handed $W$ Bosons and Heavy $W^\prime$ in $p\bar p$
  Collisions at $\sqrt{s} =$1.8 TeV

abstract:
  We report on a search for right-handed $W$ bosons ($W_R$). We used data
collected with the D{\O} detector at the Fermilab Tevatron $p\bar p$ collider
at $\sqrt{s}=$1.8 TeV to search for $W_R$ decays into an electron and a massive
right-handed neutrino $W_R^\pm \to e^\pm N_R$. Using the inclusive electron
data, we set mass limits independent of the $N_R$ decay: $m_{W_R}>650$
GeV/c$^2$ and $m_{W_R}>720$ GeV/c$^2$ at the 95% confidence level, valid for
$m_{N_R}<{1/2}m_{W_R}$ and $m_{N_R} \ll m_{W_R}$ respectively. The latter also
represents a new lower limit on the mass of a heavy left-handed $W$ boson
($W^\prime$) decaying into $e \nu$. In addition, limits on $m_{W_R}$ valid for
larger values of the $N_R$ mass are obtained assuming that $N_R$ decays to an
electron and two jets.


title: $B$ Physics with the CDF Run II Upgrade

abstract:
  We summarize Run I results relevant to an analysis of the CP asymmetry in
$B\to J/\psi K_s$, the CDF upgrade plans for Run II, and some of the main $B$
physics goals related to the exploration of the origin of CP violation.


title: Tau Physics with Polarized Beams

abstract:
  We present the first results on tau physics using polarized beams. These
include measurements of the $\tau$ Michel parameters $\xi$ and $\xi\delta$ and
the $\tau$ neutrino helicity $h_\nu$. The measurements were performed using the
SLD detector at the Stanford Linear Collider (SLC). (Invited talk at the 1995
International Europhysics Conference on High Energy Physics, Brussels, Belgium,
July 27 - August 2, 1995.)


title:
Observation of Highly Virtual Photon-Photon Collisions to Hadrons at
  TRISTAN

abstract:
  We have observed highly virtual ($Q^2>1.05 GeV^2$) photon-photon collisions
to hadronic final states at $\sqrt{s_{e^+e^-}}=58 GeV$. The integrated
luminosity of the data sample was 241pb$^{-1}$. Both scattered beam-electrons
and scattered beam-positrons were detected using low-angle calorimeters (i.e.,
both photons were highly virtual, "double-tag"); we obtained 115 hadronic
events with an estimated background of $10.2\pm1.1$. The cross section obtained
was $4.11\pm0.66$pb in the $2<W_{\gamma \gamma}<25$ GeV and $Q^2_{\gamma,
min}>2$ GeV region, while the lowest order quark-parton model predicted 3.00pb.


title:
Asymmetries between the production of D+ and D- mesons from 500 GeV/c
  pi- nucleon interactions as a function of xF and pt**2

abstract:
  We present asymmetries between the production of D+ and D- mesons in Fermilab
experiment E791 as a function of xF and pt**2. The data used here consist of
74,000 fully-reconstructed charmed mesons produced by a 500 GeV/c pi- beam on C
and Pt foils. The measurements are compared to results of models which predict
differences between the production of heavy-quark mesons that have a light
quark in common with the beam (leading particles) and those that do not
(non-leading particles). While the default models do not agree with our data,
we can reach agreement with one of them, PYTHIA, by making a limited number of
changes to parameters used.


title: Recent results from CLEO on Charm and Bottom hadrons

abstract:
  In this talk, I present new results from CLEO on charm and bottom hadrons.
Most of the talk will be on the issue of the B semileptonic branching fraction,
its connection to the number of charm quarks produced in the decay of a b
quark, and the rate for the b -> ccbars transition


title:
Search for charged Higgs decays of the top quark using hadronic tau
  decays

abstract:
  We present the result of a search for charged Higgs decays of the top quark,
produced in $p\bar{p}$ collisions at $\surd s =$ 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.7$\pm$0.7~pb$^{-1}$, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.


title: Elastic Photoproduction of $\rho^{0}$ Mesons at HERA

abstract:
  The cross section for the elastic photoproduction of \r0 mesons ($\gamma p
\to \rho^0 p$) has been measured with the H1 detector at HERA for two average
photon-proton centre-of-mass energies of 55 and 187 GeV. TheFcenterline lower
energy point was measured by observing directly the $\rho^{0}$ decay giving a
cross section of $9.1\pm 0.9 (\stat)\pm 2.5 (\syst) \mu$b. The logarithmic
slope parameter of the differential cross section, ${\rm d}\sigma/{\rm d}t$, is
found to be $10.9 \pm 2.4 (\stat) \pm 1.1 (\syst) $GeV$^{-2}$. The \r0 decay
polar angular distribution is found to be consistent with s-channel helicity
conservation. The higher energy cross section was determined from analysis of
the lower part of the hadronic invariant mass spectrum of diffractive
photoproduction and found to be $13.6\pm 0.8 (\stat)\pm 2.4 (\syst) \mu$b.


title: Diffraction at HERA: experimental perspective

abstract:
  Measurements of diffractive phenomena observed at HERA are reviewed. A short
introduction to the theoretical background is presented. The review focuses on
the current experimental directions and discusses the exclusive production of
vector mesons, the deep inelastic structure of diffraction and complementary
information from jet structures. Emphasis is placed on the current sources of
background and the experimental uncertainties.


title: Top Quark Physics at the DZero Experiment

abstract:
  In this paper I present the latest results on top quark physics from the
DZero collaboration since the discovery of the top quark in March 1995. I
summarize the discovery results, discuss progress since the discovery, and show
how we can measure the top quark mass using three separate techniques. The
measurements were made at the Fermilab Tevatron, a ppbar collider with sqrt(s)
= 1.8 TeV, using 50 pb^-1 data collected from 1992 to early 1995.


title:
Azimuthal Correlations in the Target Fragmentation Region of High Energy
  Nuclear Collisions

abstract:
  Results on the target mass dependence of proton and pion pseudorapidity
distributions and of their azimuthal correlations in the target rapidity range
$-1.73 \le \eta \le 1.32$ are presented. The data have been taken with the
Plastic-Ball detector set-up for 4.9 GeV p + Au collisions at the Berkeley
BEVALAC and for 200 $A\cdot$GeV/$c$ p-, O-, and S-induced reactions on
different nuclei at the CERN-SPS. The yield of protons at backward rapidities
is found to be proportional to the target mass. Although protons show a typical
``back-to-back'' correlations, a ``side-by-side'' correlation is observed for
positive pions, which increases both with target mass and with impact parameter
of a collision. The data can consistently be described by assuming strong
rescattering phenomena including pion absorption effects in the entire excited
target nucleus.


title:
Inclusive jet cross section in ${\bar p p}$ collisions at $\sqrt{s}=1.8$
  TeV

abstract:
  The inclusive jet differential cross section has been measured for jet
transverse energies, $E_T$, from 15 to 440 GeV, in the pseudorapidity region
0.1$\leq | \eta| \leq $0.7. The results are based on 19.5 pb$^{-1}$ of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with $E_T>200$ GeV is significantly
higher than current predictions based on O($\alpha_s^3$) perturbative QCD
calculations. Various possible explanations for the high-$E_T$ excess are
discussed.


title: Measurement of Elastic $\phi$ Photoproduction at HERA

abstract:
  The production of $\phi$ mesons in the reaction $e^{+}p \rightarrow e^{+}
\phi p$ ($\phi \rightarrow K^{+}K^{-}$) at a median $Q^{2}$ of $10^{-4} \
\rm{GeV^2}$ has been studied with the ZEUS detector at HERA. The differential
$\phi$ photoproduction cross section $d\sigma/dt$ has an exponential shape and
has been determined in the kinematic range $0.1<|t|<0.5 \ \rm{GeV^2}$ and $60 <
W < 80 \ \rm{GeV}$. An integrated cross section of $\sigma_{\gamma p
\rightarrow \phi p} = 0.96 \pm 0.19^{+0.21}_{-0.18}$ $\rm{\mu b}$ has been
obtained by extrapolating to {\it t} = 0. When compared to lower energy data,
the results show a weak energy dependence of both $\sigma_{\gamma p \rightarrow
\phi p}$ and the slope of the $t$ distribution. The $\phi$ decay angular
distributions are consistent with $s$-channel helicity conservation. From lower
energies to HERA energies, the features of $\phi$ photoproduction are
compatible with those of a soft diffractive process.


title:
Factorial and Cumulant Moments in $e^{+}e^{-}\to$ Hadrons at the Z$^0$
  Resonance

abstract:
  We present the first experimental study of the ratio of cumulant to factorial
moments of the charged-particle multiplicity distribution in high-energy
particle interactions, using hadronic Z$^0$ decays collected by the SLD
experiment at SLAC. We find that this ratio, as a function of the moment-rank
$q$, decreases sharply to a negative minimum at $q=5$, which is followed by
quasi-oscillations. These features are insensitive to experimental systematic
effects and are in qualitative agreement with expectations from
next-to-next-to-leading-order perturbative QCD.


title:
Energy Flow in the Hadronic Final State of Diffractive and
  Non-Diffractive Deep-Inelastic Scattering at HERA

abstract:
  An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic $ep$ scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.


title: Atomic Electron Motion for M\"oller Polarimetry in a Double-Arm Mode

abstract:
  We analyse an effect of electron Fermi motion at atomic shells on the
accuracy of electron beam polarization measurements with a M\"oller polarimeter
operating in a double--arm mode. It is demonstrated that the effect can result
in either {\it increase} or {\it decrease} of the measured polarization
depending on the detector positions. The effect is simulated for the M\"oller
polarimeter to be installed at CEBAF Hall A.


title: Recent Results on B Meson Oscillations

abstract:
  This paper presents recent time-dependent measurements of neutral B meson
oscillations. Similar to the $K^0$--$\bar{K}^0$ system, there are two such
systems involving the b quark: $B_d^0$--$\bar{B}_d^0$ and
$B_s^0$--$\bar{B}_s^0$. Thus the physical states are respectively $K_{S}$ and
$K_{L}$, $(B_d)_S$ and $(B_d)_L$, and $(B_s)_S$ and $(B_s)_L$. The oscillation
between each pair of states can be used to determine their mass difference. The
present world average for the $(B_d)_S$--$(B_d)_L$ mass difference is $\Delta
m_d = 0.457\pm0.019 ps^{-1}$ (or $(3.01\pm0.13)\times 10^{-4}$ eV). Using
$f_{B_s}$ = 12\% (the fraction of $B_s$ produced in b events), the current
lower limit on the corresponding $\Delta m_s$ is 6.1 ps$^{-1}$ (or $4.0\times
10^{-3}$ eV).


title: Dark Matter Search with Moderately Superheated Liquids

abstract:
  We suggest the use of moderately superheated liquids in the form of
superheated droplet detectors for a new type of neutralino search experiment.
The advantage of this method for Dark Matter detection is, that the detector
material is cheap, readily available and that it is easily possible to
fabricate a large mass detector. Moreover the detector can be made "background
blind", i.e. exclusively sensitive to nuclear recoils.


title: Masses and Lifetimes of B Hadrons

abstract:
  The latest measurements of the masses and lifetimes of weakly decaying
$B$~hadrons from experiments at $e^+e^-$ and $p\bar{p}$ colliders are
presented. These measurements include the lifetimes of the $\bar{B}^0$,
$\bar{B}^0_s$, $B^-$, and $b$~baryons, as well as searches for the $B_c$~meson.
The observation of $B^*$, p-wave B~mesons ($B^{**}$), and excited $b$~baryons
using inclusive and exclusive $B$~hadron reconstruction are discussed. Results
on $b$~quark flavour tagging are given. The latest measurements of the masses
and lifetimes of weakly decaying $B$~hadrons from experiments at $e^+e^-$ and
$p\bar{p}$ colliders are presented. These measurements include the lifetimes of
the $\bar{B}^0$, $\bar{B}^0_s$, $B^-$, and $b$~baryons, as well as searches for
the $B_c$~meson. The observation of $B^*$, p-wave B~mesons ($B^{**}$), and
excited $b$~baryons using inclusive and exclusive $B$~hadron reconstruction are
discussed. Results on $b$~quark flavour tagging are given.