test chiral quantum numbers. For smuon mass measurement the worst background coming from $W^+W^-$ final states can easily be suppressed with right-handed electron/left-handed positron beams, as shown in fig \[fig:pol\](a,b) from [@nauenberg]. The selectron mass measurement, thanks to larger production cross sections, can greatly be improved by a double subtraction of $e^+$ and $e^-$ energy spectra and opposite electron beam polarizations, see fig. \[fig:pol\](c). In both cases the endpoints from $\tilde{\mu}_{L,R}$ and $\tilde{e}_{L,R}$ are clearly exposed giving rise to precise determination of slepton masses. New techniques have been also developed [@Gerbode:2005ke] to isolate from SM backgrounds the selectron-decay signal in the forward region ($|\cos\theta|>0.8$) which in some scenarios carries most of the information constraining the selectron mass. With new selection techniques it has been demonstrated that the selectron signal can be separated from Standard Model backgrounds through the entire forward tracking region $|\cos \theta| < 0.994$.

(a)![(a,b) Energy spectra of muons from $\tilde{\mu}_{L,R}$ decays into $\mu\tilde{\chi}^0_1$ including $W^+W^-$ background for two combinations of beam polarisations $P_{e^-},P_{e^+}$: (a) $-$80%,+80%, (b) +80%,$-$80%). (c) Difference of $e^+$ and $e^-$ energy spectra from selectrons $\tilde{e}_{L,R}$ produced with polarised beams; from [@nauenberg]](emLepR.ps "fig:"){width="4cm" height="3cm"} (b)![(a,b) Energy spectra of muons from $\tilde{\mu}_{L,R}$ decays into $\mu\tilde{\chi}^0_1$ including 