Hasty Overview of Photon + METStudies in the Context of GMSB

Bruce SchummJoint SUSY/UED Meeting23 November 2010

Significant Transition: MGM to GGM

Tevatron analysis based on “Snowmass Points and Slopes” trajectory that is essentially Minimal Gauge Mediation (MGM)

MGM ties strong (gluino) and EW (neutralino) partner scales together, and leads to very massive gluino

Tevatron analyses exploited weak production (lot of data at low energy); sets limits on neutralino mass

MGM not particularly well motivated look at Generalized Gauge Mediation (GGM) which decouples strong, EW scales

Re-cast in terms of limits in Mg-M plane for each of three possible neutralino species: Bino-, Wino-, Higgsino-like

Production cross-section (7TeV)

Bino - like Neutralino: |M1| << and |M1| < |M2|; M of Neultralino NLSP ~ M1, Neultralino NLSP + Gravitino (76%)

For Bino-like neutralino, two photons + MET is most promisingbut lose coverage if hadronic activity is required (jets, HT, etc.)

No visible jet activity when

Mg ~ M

Thanks to Shih/Ruderman, ArXiv 0911.4130

MGM trajectory

Production cross-section (7TeV)Wino - like Neutralino: |M2|<< and |M2| < |M1|

Natural for photon+lepton channel

Not shown: Higgsino, which has no photonic decay, but a partial admixture might show up in photon + jet(s)

Analysis Details (largely a list of items without specifics; see sharepoint(?)… not optimized yet since signal MC just becoming available)

• Trigger: • EF_g10_loose period E2 and before• EF_2g15_loose after period E2

• Data streams: various (AOD, Susy D2PD, SUSY D3PD)

• SUSY Good-Run-List (GRL)

• Photon • Defintion: RobustTight• || < 2.37 and not in crack region• Isolation: EtCone20/Et < 0.1(see next slide)• Require two photons: E1 > 30 GeV; E2 > 20 GeV

• Overlap removal

• Jet cleaning, OTX, good primary vertex…

Real photons (signal, QCD direct-)

Fake photons (jet)

Photon Isolation Requirement

Fairly strong preference for ETCone/ET. Since jet backgrounds not expected to dominate, choose loose cut ETCone/ET < 0.1.

MET

We will use RefFinal

MET cut not yet chosen; typically would be ~100 GeV(or: use no MET cut?)

SUSY “standard” is SimpRefFinal, but this contains no explicit photon term

BACKGROUNDS – ROUGH OUTLINE

Basic Idea: Use control samples to constrain MET shapes of various background processes. Normalize to data in control regions.

Backgrounds without instrinsic MET

• Two real photons: • MET from Z ee

• One photons, one jet photon• MET from tight/loose photon control sample

• Two jet photon• MET from loose/loose control sample?

• Fit region MET < 30 GeV (?) to normalize separate contributions

Composition of Photon-Loose Control Sample(Single photon)

Single-photon control sample: Data vs. MC

We know there are K-factor uncertainties, but we can see that jet fakes are not horribly out of whack.

Next up: di-photon control sample

Backgrounds with intrinsic MET

• Assumption that this is dominated by e fakes in W, ttbar, etc.

• MC suggests 85-90% of background is e ; remainder is jet

• Control sample is e (veto if second )

• Have started with tight photon + medium electron, but are wondering if tight/tight is better (future triggers a consideration)

• Derive fake content by applying e rate measure via Z sample tag-and-probe

• Still need to separate out component with intrinsic MET from that (such as Ze) without, since the Z fakes will be accounted for in the no-MET control sample

GMSB1 SPS8 BG (Z,W,Z,W, ttbar)

0e2p 1e1p 1e1p(excl)

0e2p 1e1p 1e1p(excl)

0e2p 1e1p 1e1p(excl)

All 62 +/- 8 17 +/- 4 3649749+/- 1910

EventEmFract> 0.05

57+/- 7.5 16+/- 4 511279+/- 715

Npho/ Nelec

29.0+/- 5.4

13.2 +/- 3.6

6.3 +/- 2.5

8.2+/- 2.9

2.2 +/- 1.5

1.1 +/- 1.0

698 +/- 26

8919 +/- 94

8908 +/- 94

Met > 50 GeV

23.4+/- 4.8

10.7 +/- 3.3

5.2+/- 2.3

7.2+/- 2.7

2.0 +/- 1.5

0.96+/- 0.98

19 +/- 4 77+/- 9 76+/-9

HT > 150 GeV

23.3+/- 4.8

10.7 +/- 3.3

5.2+/- 2.3

7.1+/- 2.7

2.0 +/- 1.5

0.96+/- 0.98

16 +/- 4 67+/-8 66+/-8

e Control Sample Composition (helps to reject eventswith second hard photon)

Electroweak contribution to the e control sample

• Dominated by Z at low MET

• Use to estimate background for MET about ~100 GeV

Comparison of “signal” (two photons) to “control” (one electron/one photon; reject if second photon)

Systematics to Consider

Event Selection Systematics

• Trigger (and skim if used) • Photon identification and selection• Et scale (Et cut)• MET response (MET cut)• Isolation cut (Model dependence)• Object quality (OTX cut)• Pileup effects

Cross Section Uncertainties

• Parton distributions• K Factors

More Systematics to Consider

Background Systematics

• Control sample statistics- low MeT normalization of QCD background- e sample- e rate determination

• Relative amount of jet vs. direct photon in QCD background• Non e backgrounds with intrinsic MET

Luminosity Uncertainty

Additional needs/opportunities

• Photon efficiency from Zee?

• Limit formalism (fit to MET spectrum?)

• Trigger studies

• Strong ISR

• Other discriminating varilables (HT, , M, …)

• Non-pointing photons

• Wino/Higgsino-like analyses (single-photon + XXX?)

• Work on reducing e rate (extra hits, B-layer outliers…)

• Other ideas…