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Physics with Photons and Missing Energy at ATLAS

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. SCIPP Roles Played.

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Physics with Photons and Missing Energy at ATLAS

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  1. 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

  2. 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

  3. 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

  4. Full 2011 diphoton + MET result (5 fb-1) in Collaboration-Wide Review for ICHEP and then Phys. Lett. B

  5. 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

  6. 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)

  7. GMSB Phenomonology • Hidden gauge sector breaks SUSY via weakly-coupled messenger interactions • LSP is light (<< 1 GeV) gravitino • NLSP is typically neutralino 01 • Bino-like neutralino is natural, which decays with ~75% BF to photon-gravitino • 2 photons + missing transverse energy (MET) 01 could also be admixture of Wino, Higgsino  Photon + (lepton, bjets) + MET

  8. 5 fb-1 Diphoton+MET Strategy • Tighter photon selection suppresses backgrounds • Three analysis regions targeting A: High-mass (strong) production, heavy 01 B: High-mass production, light 01 C: Low-mass (electroweak) production Analysis Cuts Observed Signal Expected Background

  9. 5 fb-1 Diphoton+MET Results • Tighter photon selection (no pixel hits for conversions) • Optimized signal regions & highter photon ET thresh •  ~100 GeV greater reach than CMS (like x3 stats):

  10. New Analysis I:  + bjets + MET

  11.  + bjet + MET Motivation and Search • One photon, ET > 125 GeV • MET > 150 GeV • 2 ET > 50 jets, one b-tagged • min > 0.4 • MT(,MET) > 100 GeV • Lepton veto Shih, Ruderman

  12.  + bjet + MET: Prospects First analysis of cascade involving photon + bjet For 01 ~50/50 h/B mix, can approach mg ~ 700 GeV when m > ~200 GeV Target: SUSY2012 Beijing, Aug 13-18

  13. New Analysis II: Photon + Lepton + MET • “Lead” is Jovan Mitrevski • Target EW production, and bino/wino admixture for 01) • 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 Wino-like NLSP Shih, Ruderman

  14.  + Lepton + MET Prospects Background approach nearing completion Systematics ~ next week Histogram-fit limits ~ 2weeks Hope to make SUSY12 TCR SR QCD XR1 WCR XR2 W

  15. Photon(s) + MET Summary 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

  16. BACKUP

  17. General Gauge Mediation (GGM) • 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 10 masses:

  18. Data-Driven Background Estimate • 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

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

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

  21. 7/25/11: Accepted (pending small revisions)

  22. Observed in Signal Region vs. Expected Background

  23. 20101 (~1 fb-1) Analysis 2011 30x increase in data sample size  12x improvement in cross-section limit 2010 But:   1/M9 for Mgluino~ 900 GeV!

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