DiPhoton + MET: Towards Unblinding of the 5 fb -1 Analysis

1. DiPhoton + MET: Towards Unblinding of the 5 fb-1 Analysis Bruce Schumm 29 Feb 2012 • Reminder about 1 fb-1 analysis • New strategy: A B C analyses • Optimization • MET Blues • Background estimates • Unblinding of A, preparation for B unblinding

2. 1 fb-1 Analysis: Thumbnail Sketch • (First-order) signal selection straightforward: •  2 tight isolated photons with ET  25 GeV • ETmiss  125 GeV • Optimization based only on ETmiss cut value • Optimization geared towards high-mass Gluino for broad range of bino masses (50 GeV to Mgluino)

3. Analysis Improvements Overlap Criteria - Reverse /e overlap criterion (have medium e kill ) - e  fake rate goes from 0.049-0.168 to 0.025-0.075 - 13% signal efficiency loss Conversion pixel requirements - Conversion tracks can have no pixel hits - e  backgrounds reduced by 43% (42% for events with one conversion; 61% for events with two conversions) - 13% signal efficiency loss Conversion categories - Division into three conversion categories suggested - No benefit if background is ~0

4. Optimization: General Principles • Two scales characterize GMSB production/decay • Missing energy (mostly bino mass; also bino boost)  MET • Total energy, including photons (sparticle mass)  HT • Analysis A: High-mass sparticle, high-mass bino • Large MET, moderate HT • Analysis B: High-mass sparticle, low-mass bino • Moderate MET, large HT • Analysis C: SPS8 (direct gaugino production; sparticles too heavy) • Moderate-to-large MET; NO HT (most like 1 fb-1 analysis) • Also: 1 fb-1 backgrounds observed to have photons close to MET •   (photon to MET) cut explored for A,B,C analsyes

7. C

8. Optimization of A, B, C Points: Results Optimization results: All use photon ET > 50 GeV. Figure of merit rather flat in   use either 0.5 or no cut Drop unjustified significant digits

9. Background: Definition of “QCD” Control Samples We model the ETmiss distribution of selected events with no intrinsic missing energy via two control samples: QCDg and QCDgg. A “control photon” satisfies the loose, but not the tight, selection requirement for two shower quantities: the shower shape in the shower core {fracs1} and the shower width {weta1} in the first sampling of the electromagnetic calorimeter. QCDg has one such control photon; QCDgg has two.

10. QCDg, QCDgg, and gg – MET_SimpRefFinal No resemblance of control sample eTmiss shape to that of the signal 2/16/2012 10

11. QCDg, QCDgg, and gg – MET_LocHadTopo N.B.: Studies with +Njets MC suggest high-ETmiss tails a bit larger for SimpMetRefFinal  Propose to use LocHadTopo for ETmiss 2/16/2012 11

12. BACKGROUNDS E- Control Sample (Penn) QCDg Control Sample (DESY) Overlap ? (DESY) Missed? (SCIPP)

13. EW Background from e- control sample Brig, Jack N.B.: “Signal” is e-

14. Scale factors from Ze/Zee Multiply these by “signal” numbers on previous page

17. Pseudo-photon control sample (Peter, Martin) SIGNAL BLINDED FOR MET > 100 GEV • QCDg distribution provides shape and tails • scale to signal (gamma-gamma) in low-MET region (ETmiss<20 GeV) SIGNAL BLINDED FOR MET > 100 GEV SIGNAL BLINDED FOR MET > 100 GEV

18. Background Summary *Includes a 0.2 event contribution from “irreducible” backgrounds (two real photons) that are negligible in A and B regions; needs to be checked for C Missed/Overlapped backgrounds study: No significant corrections suggested (up to smallish uncertainties)

19. A word on the 5 fb-1 reach (not fully-optimal analyses) A: ggm_900_800   -> LL: 142.4, sig: 16.9, #S: 21.3, #B 0.01 ggm_1000_800 -> LL: 39.8, sig: 8.9, #S: 7.1, #B 0.01 ggm_1100_800 -> LL: 10.8, sig: 4.7, #S: 2.4, #B 0.01 ggm_1200_800 -> LL: 3.4, sig: 2.6, #S: 0.9, #B 0.01 C: sps8_170 -> LL: 22.2, sig: 6.7, #S: 11.9, #B 0.9 sps8_180 -> LL: 14.5, sig: 5.4, #S: 8.9, #B 0.9 sps8_200 -> LL: 6.6, sig: 3.6, #S: 5.3, #B 0.9 sps8_220 -> LL: 2.7, sig: 2.3, #S: 3.0, #B 0.9 sps8_240 -> LL: 1.2, sig: 1.5, #S: 1.8, #B 0.9 B: ggm_900_50   -> LL: 45.1, sig: 9.5, #S: 10.3, #B 0.05 ggm_1000_50 -> LL: 13.6, sig: 5.2, #S: 4.0, #B 0.05 ggm_1100_50 -> LL: 2.7, sig: 2.3, #S: 1.2, #B 0.05 ggm_1200_50 -> LL: 0.4, sig: 0.85, #S: 0.3, #B 0.05 Limits for 1 fb-1 about 820 GeV for analysis-A-like scenario and ~145 TeV for SPS8 trajectory

20. Unblinding Procedures • Obtain Ed-Board approval (done 2/21/12) • Examine HT sidebands to build confidence in background modeling, especially without the  cut (B analysis) • Since B sidebands (up to HT=1100 GeV) are almost A signal region (HT > 600 GeV) explore and unblind A before exploring B sidebands

21. HT Sidebands for Analysis A: 200 < HT < 400 Includes  cut MET Cut

22. HT Sidebands for Analysis A: 400 < HT < 600 Includes  cut MET Cut

23. Analysis A Unblinded Includes  cut No signal for MET > 200; Should set strong limit for high Bino mass (note that 200 GeV cut has avoided one background event)

24. Analysis B Blinded HT > 1100 No  cut

25. HT Sidebands for Analysis B: 500 < HT < 800 500 < HT < 800 No  cut

26. HT Sidebands for Analysis B: 800 < HT < 1100 800< HT < 1100 No  cut How well do we understand these backgrounds? Should we fear not using the  cut?

27. e- Control Sample (EW Bkgds); No  Cut Scale by e rate to get expected background

28. e- Control Sample (EW Bkgds); No  Cut Scale by e rate to get expected background

29. 200 < HT < 1100 Sideband: Expected (assuming no signal) vs. Observed Rates With  cut

30. 200 < HT < 1100 Sideband: Expected (assuming no signal) vs. Observed Rates  cut removed

31. Summary • Three analyses geared towards high&low mass bino, SPS8 • High-mass bino analysis: 0 signal events • Low-mass bino ready to unblind; SPS8 requires further background studies (underway) • Verbatim 2011 analysis applied to 5 fb-1  150-200 GeV increase in limits • 2012 analysis improvements  250-400 GeV increase • CMS did better than ATLAS with 1 fb-1 because of • More favorable interpretation of GGM model • Luck • but per fb-1, our analysis was more sensitive

32. BACKUP

33. Also: Limit of  > 145 TeV set on SPS8 SUSY Breaking scale Analysis background-limited; sparticle cross section goes as ~M-9  reoptimize!

34. Photon Et Optimization (1 fb-1 Analysis) Helenka Choose Cut of 50/50

35. Cross-check with MET distribution from Zee (background real ?)

36. No QCDg above 100 GeV  Less than 1 event at 95% CL

38. Overlap Between QCDg and EW backgrounds Martin

41. Missed Backgrounds (?) Dan • Since our “QCD” backgrounds are estimated by normalizing control samples (QCDg, Zee) to low-MET signal, they should be comprehensively accounted for • “EW” (W,top) backgrounds estimated via e- control sample  Assumes all W,top contributions have at least one e fake • Is this true? If not, what is character of the “missed” component? • Might the “missed” component in fact be incorporated into the QCD control sample (pseudo-photon) estimate?

42. According to MC, what fraction of EW background is due to e fakes? MC

43. Of the 25% that is “missed” 18.9% + 47.5% = 66.4%  2/3 is expected to be reflected in the pseudo-photon sample This 2/3 may well be the source of the “EW-contamination” in the pseudo-photon sample (cross-check underway This component is neither missed nor double-counted!  Add “QCD” and “EW” backgrounds linearly (values and errors)