1. 1 Update: High energy photon pairs Vladimir Litvin, Toyoko Orimoto Caltech 04 December 2007

2. 2 Introduction Search for RS-1 gravitons decaying into two high energy photons MC Samples: Produced at Caltech & Fermilab (with no pileup) Signal RS-1 G  : X k events in 167 & 171 for 750, 1250, 1000, & 1500 GeV mass samples (with c = 0.1) Reducible and irreducible backgrounds: Born: ~80k events Box: ~80k events Brem (preselected): ~X k QCD (preselected): ~X k bornbox

3. 3 Comparison of HLT EG in 167 vs 171 E-gamma HLT path efficiencies 167 171 Appears that EG efficiencies in HLT have changed significantly from 167 to 171

4. 4 Selection: photon pt Red = 167 Blue = 171 Born bkgBox bkg Higher Et photon Lower Et photon

5. 5 Selection: ECAL Iso Red = 167 Blue = 171 Born bkgBox bkg Higher Et photon Lower Et photon Strange peaks

6. 6 Selection: H/E Red = 167 Blue = 171 Born bkgBox bkg Higher Et photon Lower Et photon More narrow H/E distributions

7. 7 Selection: Tracker Isolation (N_tracks) Red = 167 Blue = 171 Born bkgBox bkg Higher Et photon Lower Et photon Decrease in tracking efficiency?

8. 8 Selection: Tracker Isolation (pt_tracks) Red = 167 Blue = 171 Born bkgBox bkg Higher Et photon Lower Et photon Significant change in tracker isolation distributions

9. 9 Conclusions Significant differences seen between 167 and 171, both at HLT level and analysis level Due to changes in tracker efficiency? Are others seeing this also?