1 Tuning des coupures tights Fany Dudziak RD. Schaffer, L. Iconomidou Fayard Réunion de physique du LAL Le 10 septembre 2009

2 Résumé. -> Problèmes pour reprocesser egamma sur les AOD -> Efficacités : old vs new -> Rejection : old vs new -> Zoom sur les TRT cuts.

3 Pit-falls going from AOD->DPD Rerun egamma starting from AOD and write out a DPD. Useful for many purposes. Consistency check: Loop on clusters and redo electrons without any change:  Do trackmatch  Rerun egamma for calibration and Identification (isEM)  Create a NewElectronAODContainer Compare electrons in “ElectronAODContainer” and “NewElectronAODContainer” Without any action one would expect the two sets of electrons to be identical. Not true! Actually there are few pit-falls:  Should be careful about version of calibration hit file used during re- calibration.  Don’t use in AOD isBarrel and isEndcap to know where a cell is: both equal to 1!. Even after these pit-falls one finds differences:  Energy info is truncated in writing AOD. Running egamma from AOD clusters give slightly different results (see plot next slide)  Missing info: scintillator and tile cells not all present in AOD. Affects ethad re-calculation (and then identification)

4 Cluster energy difference Gaussian RMS=~ 4MeV. Some tails. Distribition flat in Eta.

5 Difference in Identification (isEM) Test with a set of H->4e Electron AODContainer NewElectron AODContainer Difference In nb electrons Generated3720 Container (+5,-4) (probably deta) Loose (9cont+ 12 hadleakage (+-) 7 (e37/377+width)(+-) Strips (18 loose +2strips)

6 Optimisation Δ φ (track-calo) Very sensitive to brem : -> when electron radiates it looses energy and is bent more and more in the magnetic field.  Dependance in Pt (brem effect more problematic at low Pt) Cut at 0.02 for the moment: not optimal, cuts all the electron with hard brem (-1.5% wrt medium level) Symmetric on ا Δφ ا => propose an asymmetric cut ΔφΔφ

7 Efficacités 15.3 vs new tight Zeeoldnew Container95.91%95.92 Loose92.14%92.40 Medium - Δη87.82%88.06 Medium87.72% Δ φ 81.39% E/P79.35% TRT hits77.65% TRT ratio74.26%77.02 Tight (Blayer)72.17%74.24

8 Fake rates 15.3 vs new tight Jf17oldnew Loose3.9 x10-3 Medium - Δη1.1 x10-3 Medium6. x Δ φ 4. x E/P3. x TRT hits3. x TRT ratio2. x10-4 Pas de Blayer et pas d’isolation

9 TRT cuts : TRT hits Nb TRT hits – facteur de correction dépendant de eta Signal bkg On coupe à -15 mais pas discriminant => Enlève presque plus de signal que de bruit de fond

10 TRT ratio Signal bkg « ratio of high to all TRT hits for isolated electrons »

11 Conclusion Faire fonctionner egamma sur les AOD est loin d’être simple: –> ~ compris pour le signal –> pour le bruit de fond facteur 4 au niveau container + problèmes supplémentaires à cause de leakage hadronic? Efficacités : –Δη à relacher pour quelques bins et ça devrait etre bon, –Bonne robustesse pour les autres coupures (+3% au final)