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Physics with Photons and Missing Energy at ATLAS DOE Site Visit Thursday June 14, 2012 Damiani *, Kim, Kuhl, Litke, Mitrevski, Nielsen, Schumm (convener) Collaborators: Annecy, DESY, La Plata, Liverpool, Penn, Tokyo Tech, Wiezmann * Ph.D. June 2012
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SCIPP Roles Played Diphoton + MET (flagship photon + MET analysis) Schumm convener, cast of ~ dozen Damiani thesis Photon + Bjets + MET Nielsen, Kuhl, with Weizmann Photon + Lepton + MET Mitrevski Overall Photon(s) + X + MET Schumm is contact person
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Papers Search for Diphoton Events with Large Missing Transverse Momentum in 1 fb -1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector Phys. Lett. B710 (2012) 519-537 Search for Diphoton Events with Large Missing Transverse Momentum in 36 pb-1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector Eur. Phys. J. C71 (2011) 1744
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Full 2011 diphoton + MET result (5 fb -1 ) in Collaboration- Wide Review for ICHEP and then Phys. Lett. B
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ATLAS Recognition Invited Talks Mitrevski: Photons+MET, SUSY11, Aug 2011 Schumm: SUSY @ ATLAS, CIPANP, May 2012 US Talks Schumm: SUSY @ ATLAS, SUSY Recast (Davis), April 2011 Mitrevski: Photons+MET, BNL SUSY Workshop, May 2011
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Photon(s) + MET: Motivation ATLAS searches defined by signature, motivated by one or more BSM physics scenario. Photon(s) + MET Motivations: Gauge-Mediated SUSY Breaking (GMSB) New “hidden” gauge/messenger sector protects flavor symmetry Photons from gaugino gravitino decay Universal Extra Dimensions (UED) Weak gravity excused by leaking into extra dimensions Gravity-mediated KK photon decay KK + G (KK)
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Hidden gauge sector breaks SUSY via weakly- coupled messenger interactions LSP is light (<< 1 GeV) gravitino NLSP is typically neutralino 0 1 Bino-like neutralino is natural, which decays with ~75% BF to photon-gravitino 2 photons + missing transverse energy (MET) 0 1 could also be admixture of Wino, Higgsino Photon + (lepton, bjets) + MET GMSB Phenomonology
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5 fb -1 Diphoton+MET Strategy Tighter photon selection suppresses backgrounds Three analysis regions targeting A: High-mass (strong) production, heavy 0 1 B: High-mass production, light 0 1 C: Low-mass (electroweak) production Analysis Cuts Expected Background Observed Signal
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5 fb -1 Diphoton+MET Results Tighter photon selection (no pixel hits for conversions) Optimized signal regions & highter photon E T thresh ~100 GeV greater reach than CMS (like x3 stats):
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New Analysis I: + bjets + MET
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+ bjet + MET Motivation and Search Shih, Ruderman One photon, E T > 125 GeV MET > 150 GeV 2 E T > 50 jets, one b-tagged min > 0.4 M T ( ,MET) > 100 GeV Lepton veto
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+ bjet + MET: Prospects For 0 1 ~50/50 h/B mix, can approach m g ~ 700 GeV when m > ~200 GeV Target: SUSY2012 Beijing, Aug 13-18 First analysis of cascade involving photon + bjet
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New Analysis II: Photon + Lepton + MET “Lead” is Jovan Mitrevski Target EW production, and bino/wino admixture for 0 1 ) Start with l = to avoid jet (QCD) backgrounds Backgrounds (order of size): W , tt(+ ), W+jets, Z + ( ,jets) Only existing result is CMS, 35 pb -1 EW Production Shih, Ruderman Wino-like NLSP
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+ Lepton + MET Prospects SR QCD XR1 XR2 TCR Background approach nearing completion Systematics ~ next week Histogram-fit limits ~ 2weeks Hope to make SUSY12 WCR WW
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SCIPP playing leading role in multi-signature arena Attentive analysis yields very aggressive limits 2011 (5 fb -1 ) Two papers published, one in CWR, two more in analysis stage 2012 (20 fb -1 @ 8 TeV) Expect 10-15% improvement from each of higher energy, statistics 25% increase in reach (?) Beyond 14 TeV will open up a whole new window Photon(s) + MET Summary
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BACKUP
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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)
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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
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Nothing there with 36 pb -1, so we set limits… ISO: New Physics! Signal region
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ATLAS has better photon reconstruction than CMS (conversions) Observed, Expected Limits
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7/25/11: Accepted (pending small revisions)
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Observed in Signal Region vs. Expected Background
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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!
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