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

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

4. Analysis Improvements
Overlap Criteria
- Reverse /e overlap criterion (have medium e kill )
- e  fake rate goes from to
- 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)
Conversion categories
- Division into three conversion categories suggested
- No benefit if background is ~0

5. 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

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

7. Full Optimization of A, B, C Points
Dan
Optimization strategies:
All use photon ET > 50 GeV.
A: ETmiss, HT, and 
Use GGM (Mg,MB) = (900,800)
B: ETmiss, HT (signal  too small)
Use GGM (900,50)
C: ETmiss,  (low mass scale in production so no HT)
Use SPS8; =170 TeV

11. C

12. 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
Target Model
ETmiss HT  A
(900,800)
200
600
0.5 B
(900,50)
100
1100
--- C
SPS8 170
125

13. MET Issues ETmiss Glossary:
Martin, Dan, Helenka
MET_LocHadTopo
Local Hadronic calibration applied to all topo clusters
MET_RefFinal
Based off of objects
Local Hadronic calibration used for jet objects
MET_SimplifiedRefFinal
Based off of objects (Tight photons w/ pT>20 GeV used)
EMJES calibration used for jet object
Modified version of SimpRefFinal
Based off of objects (Loose photons w/ pT>20 GeV used)
EMJES calibration used for jet objects
Doesn’t exist on D3PD
ETmiss Glossary:
LocHadTopo: Used for prior diphoton+MET analyses; not directly ATLAS-supported
Simplified MetRefFinal: SUSY-group recommended (reconstruct ETmiss from separately-treated objects)
MetRefFinal: ATLAS (but non SUSY) supported; available on SUSY D3PDs though. (Use jets with local hadronic calibration)
_ Not usable for 5fb-1 analysis; explore for future.

14. SimpMetRefFinal: Initial “Photon Fix”

15. Sample used:
+jet MC

17. 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.

18. LocHadTopo

19. !!  Must also correct loose photons!
Simplified
MetRefFinal
!!  Must also correct loose photons!

20. QCDg, QCDgg, and gg – MET_SimpRefFinal
No resemblance of control sample eTmiss shape to that of the signal
2/16/2012 20

21. 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 21

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

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

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

27. 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

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

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

31. Overlap Between QCDg and EW backgrounds
Martin

34. 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?

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

36. Of the 25% that is “missed”
No e
With e
 + 
18.9
0.0
 + jet
47.5
5.0
 + 
3.0
2.9
 + W l
22.9
18.9% % = 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)

37. Background Summary QCD EW TOT A 0.10  0.10 0.03  0.03 0.13  0.13 B C
0.7  ?
1.2  ?
1.9  ?
1 fb-1
0.8  0.7
3.1  1.5
4.1  1.7*
*Includes a 0.2 event contribution from “irreducible” backgrounds (two real photons) that are negligible in A and B regions; needs to be check for C

38. A word on the 5 fb-1 reach (not fully-optimal analyses)
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

39. Fire and Brimstone
Verbatim 2011 analysis  GeV increase in limits
2012 analysis improvements  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
Dark matter, light Higgs(?)  SUSY (??)
Possibility never greater; if something is there, don’t want to miss it!
Critical to unblind right away.

40. BACKUP

42. Diphoton+MET meeting - 09.02.2012 - Helenka Przysiezniak / LAPP
GamNp1 diphoton sel
LocHadTopo
One extra event
for
MET>100GeV
MeanRefFinal 
MeanLocHadTopo
RefFinalSimpSUSY
Diphoton+MET meeting Helenka Przysiezniak / LAPP 42

43. Diphoton+MET meeting - 09.02.2012 - Helenka Przysiezniak / LAPP
GamNp2 diphoton sel
LocHadTopo
One extra event
for
MET>90GeV
MeanRefFinal 
MeanLocHadTopo
RefFinalSimpSUSY
Diphoton+MET meeting Helenka Przysiezniak / LAPP 43

44. Diphoton+MET meeting - 09.02.2012 - Helenka Przysiezniak / LAPP
GamNp3 diphoton sel
LocHadTopo
One extra event
for
MET110 GeV
MeanRefFinal 
MeanLocHadTopo
RefFinalSimpSUSY
Diphoton+MET meeting Helenka Przysiezniak / LAPP 44

45. Diphoton+MET meeting - 09.02.2012 - Helenka Przysiezniak / LAPP
GamNp4 diphoton sel
LocHadTopo
MeanLocHadTopo 
MeanRefFinal
Both have event
for
MET200GeV
RefFinalSimpSUSY
Diphoton+MET meeting Helenka Przysiezniak / LAPP 45

46. Diphoton+MET meeting - 09.02.2012 - Helenka Przysiezniak / LAPP
GamNp5 diphoton sel
MeanLocHadTopo 
MeanRefFinal
LocHadTopo
Few extra events
for
MET80GeV
RefFinalSimpSUSY
Diphoton+MET meeting Helenka Przysiezniak / LAPP 46

47. QCDg, QCDgg, and gg – MET_RefFinal
2/16/2012 47