Data/Filtered Pythia Inv. Mass Distributions


Data Vs. T2 Platinum (see here)


  • Events pass L2gamma software trigger and (for data) online trigger.
  • candidate pt > 5.5
  • charged track veto
  • at least one good strip in each smd plane
  • Z vertex found
  • | Z vertex | < 60 cm
  • Zgg < .7
  • | particle eta | < .7


9 pt bins, with boundries {5.5, 6., 6.75, 7.5, 8.25, 9.25, 11., 13., 16., 21.}



All MC plots are normalized.  They are scaled to match the number of counts in the data between M = .08 and M = .25 GeV/c^2 (the nominal signal region.)




The above plots shows the data/mc comparison for the first four bins (the bin number is in the upper right corner.)  The MC peak position and width track relatively well to the data.  In the data, there is an excess of 'low mass' background events.  This is expected as the MC is filtered for high pt pion events and thus the background will be artificially suppressed compared to the signal.



The above plot shows the last five bins along with the total comparison for all bins (lower right)


The Data (black) and MC (red) are fit to separate gaussians between .1 and .2 GeV/c^2.  The mean masses for each are plotted below.  Apologies for the lack of axis labels.  The x-axis is pion pt and the y-axis is mean mass of that pt bin.  The errors on the points are the errors on the fits.  I would take the last bin with a grain of salt considering the stats.

The blue line is the pdg mean mass of the pion.  As you can see, the MC tracks the data very well, recreating the rising mass peak.