Two photon process veto efficiency 4-Aug-2006 A.Miyamoto Preliminary status report

Two photon background data Generator data  Generated by Kurihara san using GRACE  Full 4 fermion diagram: e+e-  e+e-  +  -, No ISR, NoBS  Conditions of event generation  Ecm = 500 GeV   prod of each final particles > 5mrad  E of each final particles : 1~500 GeV  Total Cross section  9.04 pb Distributions at generator level and result by quick simulator are studied, using 100k events, corresponding to ~11/fb

e- distribution at L=4.5m A hall by 5mrad cut at generation X(cm) Y(cm) Exit hall of r=2cm, With 14mrad crossing

Max(rd1,rd2) distribution If both e-,e+ are requested to go through exit beam hall of radius 2cm, 47 events remains for 11/fb data Max(rd1,rd2) Integral of black histogram 47 events if Max(rd1,rd2)=2cm

Missing PT of max(rd1,rd2)<2.0cm events From generator data (after tau decay) From Quick Simulator data ~20events above Pt Miss > 2.5 GeV 2.5 GeV Max(rd1,rd2)<2.0cm Evis>2.0 GeV rd1 and rd2 are determined by generator data

Azimuthal angle Of missing Pt vector From Generator data Quick Simulator Pt>5.0 events Pt>2.0 Events Azimuthal angle(Radian)

Quick Simulator: Missing Pt vs Azimuthal angle of missing Pt vector 2.5GeV limit (+- 5mrad beam pipe hall)

Preliminary Conclusion Preliminary conclusion by a wild guess from a low stat. data  For Pt > 5GeV, Loss of efficiency of about 50% by putting cut on azimuthal angle.  The region below 5 GeV : will be hard to remove two-photon ee  events Plan  Simulation of 1M events are in progress  Hope result be ready by next week Integrated luminosity  m(GeV) mrad Xing 2mrad Xing Stau search region Heavy M stau limit  m(GeV) M stau Excluded 14mrad 2mrad