Two photon processveto efficiency

4-Aug-2006A.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=4.5mA 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 blackhistogram

47 events ifMax(rd1,rd2)=2cm

Missing PT ofmax(rd1,rd2)<2.0cmevents

From generator data(after tau decay)

From Quick Simulator data~20events above Pt Miss > 2.5 GeV

2.5 GeV

Max(rd1,rd2)<2.0cmEvis>2.0 GeV

rd1 and rd2 aredetermined 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)

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(G

eV)

2

5 14mrad Xing

2mrad Xing

Stau search regionHeavy Mstau limit

m(G

eV)

Mstau

Excluded

14mrad

2mrad