1. Physics with Photons and Missing Energy at ATLAS DOE Site Visit Wednesday July 27, 2011 Bangert *, Damiani, Kim, Kuhl, Litke, Mitrevski, Nielsen, Schumm (convener) In collaboration with Liverpool, DESY, Annecy, Tokyo Tech, La Plata * Ph.D. June 2011

2. ATLAS MET-Based Analyses Analyses are signature-based: Monojets * Zero-Lepton One-Lepton Two-Lepton Multi-Lepton Photon(s) * (our focus) Inclusive  B Jet(s) * Co-analysis with Exotics group (that’s a different physics group altogether) Red indicates some form of public result available on full 2010 data sample (36 pb -1 )

3. Models Used (for inspiration and/or analysis) mSUGRA / Constrained MSSM “24-parameter” MSSM Generic MSSM parameter space (four degenerate light quarks, gluino octet, LSP) Generic GMSB (“GGM”) space (light gluino octet, light Bino NLSP, gravitino) Non-contextual SUSY partners (tau sneutrino, stop+sbottom, hadronizing scolored particles) Largely redundant model spaces Independent; may appear only in photons+MET

4. Hidden gauge sector breaks SUSY via weakly- coupled messenger interactions LSP is light (< 1 GeV) gravitino NLSP is typically Bino-like neutralino  0 1, which decays with ~75% BF to photon-gravitino  Two photons + missing transverse energy (MET) is effective signature. Gauge Mediation

5. Strong production: gluino/gluino or squark/squark dominates when colored sparticles are accessible Weak production:  1   2 0 or  1   1  dominates when only EW-charged particles are accessible In both cases, decay proceeds through NLSP  1 0  Little additional activity in limit that produced state is degenerate with NLSP. Production Mechanisms

6. Based on “minimal” SPS8 model designed for ‘Snowmass’-type comparitive studies Essentially one single phenomenological parameter, often cast as M Bino Strong partner mass tied to  1 0 scale, and is high (~ TeV)  Luminosity (lower-mass EW states) trumps energy for SPS8 analyses For 6.3 fb -1, D0 finds M  > 170 GeV at 95% CL, out of reach of 36 fb -1 2010 ATLAS sample Tevatron (2 TeV) Analyses

7. The “minimal” SPS8 model is ad hoc, selected somewhat arbitrarily as a concrete model for which different facilities could be compared In particular, no reason why EW and colored partner scales need be coupled  Generalize model so that one strong partner, one EW partner are light, all other partner masses are high (~1.5 TeV) Free parameters are gluino, Bino-like  1 0 masses: General Gauge Mediation (GGM)

8. 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 promising but lose coverage if hadronic activity is required (jets, HT, etc.) No visible jet activity when M g ~ M  Thanks to Shih/Ruderman, ArXiv 0911.4130 SPS8 Trajectory D0 Limit

9. “Recast” D0 result in terms of GGM; compare to expected LHC reach (Ruderman & Shih, arXiv:1103.6083) GGM Reach: Tevatron vs. LHC 2010 analysis (36 pb -1 ) breaks significant new ground

10. Avoid inefficiencies with very simple selection: One photon with E t > 30 GeV Another photon with E t > 20 GeV MET > 125 GeV 2010 (36 pb -1 ) Analysis Signal Region MET

11. Two major sources: MET Distribution from QCD Sources Loose photon control sample Z  e + e - to model  events MET from EW Sources (Ws, ttbar) e  control sample from data, MC Scale to  contribution with e   fake rate from Z  ee studies Data-Driven Background Estimate

12. Nothing there with 36 pb -1, so we set limits… ISO: New Physics! Signal region

13. ATLAS has better photon reconstruction than CMS (conversions) Observed, Expected Limits

14. 7/25/11: Accepted (pending small revisions)

15. More selective trigger (2g20) forces higher P t cuts Two photons with E t > 25 GeV MET > 125 GeV still Estimated backgrounds above MET=125: QCD2.3  0.9 EW2.4  1.3 Total4.8  1.5 2011 (~1 fb -1 ) Analysis

16. Observed in Signal Region vs. Expected Background

17. 20101 (~1 fb -1 ) Analysis 2010 2011 30x increase in data sample size  12x improvement in cross-section limit But:   1/M 9 for M gluino ~ 900 GeV!

18.  1 fb -1 paper in preparation  3-4 fb -1 (full 2011 run) analysis will follow But, progress with 2  +MET to be incremental Background limited (re-optimization?) Steep mass dependence  Explore other channels Photon + (b)jet + MET (Kuhl) Photon + MET (Kim; dedicated trigger) Photon + lepton + MET Non-pointing photons 2011 Analysis: What Next?

19. SCIPP playing leadership (and major technical) role in central SUSY analysis One  +MET paper in press (36 pb -1 ), one in preparation (1 fb -1 ), a third in planning (3-4 fb -1 ). Beginning to explore/develop complementary single-photon channels Talks by Bangert (Cargese 2010) Mitrevski (West-Cost Forum, SLAC) and Schumm (SUSY Recast, Davis) Photon(s) + MET Summary