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