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Diphoton + MET Analysis Update. Bruce Schumm UC Santa Cruz / SCIPP 24 January 2014 Editorial Board Meeting. Gauge Mediation Grids for 7 TeV Analysis. squark/bino grid. gluino/bino grid. For 2012 (8 TeV) Data: Replace “constrained” SPS8 grid with wino/bino grid Bino = 1 0 - PowerPoint PPT Presentation
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Diphoton + MET Analysis UpdateBruce Schumm
UC Santa Cruz / SCIPP
24 January 2014 Editorial Board Meeting
Gauge Mediation Grids for 7 TeV Analysisgluino/bino gridsquark/bino gridSPS8 TrajectoryFor 2012 (8 TeV) Data:
Replace constrained SPS8 grid with wino/bino grid
Bino = 10
Wino = degenerate triplet 1 and 20
Production through 1 20 and 1+ 1-
2011 Signal RegionsETmiss = LocHadTopo
HT = Scalar sum of all transverse energy (no ETmiss)
= minimum angle between photon and METStrong production; high-mass binoStrong production; low-massbinoElectroweak productionFor 2012: Include additional observables, for certain signal regions:
MEFF (or HT-prime) = HT + ETmiss
j = minimum angle between jet and ETmiss
Also: ETmiss is now EGamma10NoTauLoosePhotonRef
2012 Optimization StrategyStrong Production (SP1, SP2)
Largely the same as for 2011 analysis Explore MEFF, j, removal of no-pixel hit requirement for conversion tracks Tweak cuts for higher mass scales MEFF somewhat preferable; j provides no apparent advantage As for 2011, optimal point is largely background-free Optimize for (mgluino,mbino) = (1300,1050) and (1300,150)
Electroweak Production (WP1, WP2)
No real preference for MEFF, but highly correlated with ETmiss so use HT. As for strong production, two SRs (low-mass, high-mass bino) helps for high-mass bino SR; j helps for low-mass bino SR Optimal point will have few-event background Optimize for (mwino,mbino) = (600,500) and (600,100)
NEW: Model-Independent Selection (MIS)
Cut at MET for which total background approach the ~1-event level
for strong-production optimization Used wino_bino_600_500, wino_bino_500_100 for weak production> Used background distributions alone for model-independent selection
Figure of merit for 1300_150PointFigure of merit for 1300_150Point; Removing events for which converted tracks have pixel hitsRe-Examination of No Pixel-Hit Requirement Remove no-pixel-hit requirement
1300_1050 (SP1) OptimizationNumber of signal events (20 fb-1)Figure of MeritChosen pointAvoid pitfalls:
Rapidly falling signal
Fluctuating backgrounds (above dips in FOM)SP1 Optimum: (MET,MEFF) > (250,1500)
Explore (,jet)MET Cuts for SP1 Selection,MET > 0.5jet,MET > 0.5Statistics not so good, but see Improvement with ,MET cut Degradation with jet,MET cutSP1
Choose (MET,MEFF) = (250,1500)with ,MET > 0.5
Model-Independent SelectionApply cut jet,MET > 0.5EW backgroundQCD backgroundNo cut on HT or MEFF; just choose point on horizontal (MET) axis for which the backgrounds approach the ~1 event level
MET > 250 GeV
Signal Selection Results
Status of Background Estimation QCD Backgrounds
EW Backgrounds from e Fakes
Irreducible Backgrounds
Irreducible Backgrounds (for now SP1, SP2 only):
From W, (Z) events Estimate from MC samples, scaled to 20 fb-1 Very small for SP1, SP2 (before K factors that are < 3) For both, before K factors: 0.03 0.01 (stat)
QCD BackgroundsEstimates derived from scaling observed low-MET signal rates to high-MET using control samplesScale to number of signal eventsIntegral above cut provides background estimate
QCD Backgrounds ContinuedFor each SR, accumulate 8 control samples In principle, eight independent estimates; establishes systematic range
Define Pseudo-photon = loose, plus fail two shower-shape requirements (Fracs1 and Weta1).
Each control sample contains at least one pseudophoton. In addition, it must (QCDtg) or must not (QCDg) contain a tight isolated photon. For each of these two choices, we can further have
A cut of either 50 or 75 GeV on the photons (tight and pseudo)
Pseudophoton may be isolated or not 8 combinations 5 signal selections 40 QCD background estimates
Undefined no control-sample events OR no signal sample events below MET = 60 GeV
If no control-sample events above MET cut set 90% UCL
NOTE: In 2011 only one control sample (QCDg 50 non-isolated I recall)
SP1SP2: Undefined (no signal at any MET!)MISWP1WP2Does not exhibit consistency!!Propose QCDtg 50 GeV no-isolation for nominal estimate
Et CutIsolated?QCDgQCDtg75no.07+-.07< 2.375yes< 9.2undef50no.17+-.10< 1.1550yes< 4.6undef
Et CutIsolated?QCDgQCDtg75no0.5+- 0.11.4+-0.775yes< 0.653.7+-3.750no.3+-.050.6+-0.250yes0.5+-0.20.5+-0.5
Et CutIsolated?QCDgQCDtg75no.9 +- .11.4+-0.875yes.6 +- .68.4+-8.450no.8 +- .11.2+-0.550yes.7 +- .54.0+-4.0
Et CutIsolated?QCDgQCDtg75no2.7+-0.30.6+-0.475yes1.1+-1.1< 2250no2.6+-0.21.0+-0.450yes3.5+-1.6< 11
Notes on QCD Background Estimates SP2 backgrounds undefined since no signal at any MET. However, if you take this as < 2.3 low-MET signal events at 90% CL, control-sample extrapolations yield < 0.5 events at 90% CL
2011 strong-production estimates were also undefined developed extrapolation technique (underway now)
Strong-production estimates suggest very small backgrounds, systematics under control
WP1 and MIS estimates larger, but consistent from sample to sample
WP2 estimates inconsistent between QCDg and QCDtg samples. Will require further thought (Osamu Jinnouchi)
Unblind SP1, SP2 first (and perhaps also MIS for the EW grid?)
BUT WAIT
Late-Breaking News: SP2 Extrapolation Use QCDtg with Et cut of 50 GeV, and do not require g to be isolated
Best guess as to most representative control sample
Will try others (with higher statistics) to checkExpected QCD background (linear fit):
NbackQCD = -0.25 +- 0.49 (or less than 0.55 events at 90%CL)
e EW Backgrounds Start with determination of the e fake rate In bins of Separately for converted, unconverted photonse final stateee final stateFake rate is (roughly) the background-subtracted ratio of these two yields
Fake Rate Results
SP1, SP2 Backgrounds at First BlushEW background from e fakes determined by scaling observed e events by measured e fake rate.SP1: no e events observed < 0.07 events expected backgroundSP2: 1 e event observed 0.03 +- 0.03 expected backgroundsOnce QCD extrapolation studies are done, SP1, SP2 backgrounds should be in good shape.
Document and request unblinding next week? Might we also want to finish MIS background studies? (No extrapolations needed for QCD
AnalysisQCDe EWIrred.TotalSP1< 0.5< 0.07~ 0.05SmallSP2< 0.50.03~ 0.05Small
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