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SUSY with Photons and MET: Introduction and thoughts about Diphoton and Single Photon Analyses

SUSY with Photons and MET: Introduction and thoughts about Diphoton and Single Photon Analyses. Bruce Schumm 12 Sept 2011. Annecy DESY/University of Hamburg Liverpool University Tokyo Tech University of California Santa Cruz Universidad Nacional de La Plata University of Wisconsin

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SUSY with Photons and MET: Introduction and thoughts about Diphoton and Single Photon Analyses

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  1. SUSY with Photons and MET: Introduction and thoughts about Diphoton and Single Photon Analyses Bruce Schumm 12 Sept 2011 Annecy DESY/University of Hamburg Liverpool University Tokyo Tech University of California Santa Cruz Universidad Nacional de La Plata University of Wisconsin Weizmann Institute

  2. General Intro

  3. Photon processes in SUSY Collider phenomenology depends on nature of LSPs mSUGRA GMSB LSP: gravitino ( massless) NLSP: lightest neutralino production: tree level • LSP: lightest neutralino • NLSP: 2nd neutralino • production: 1-loop Signature:  + MET (+ X) This group’s focus so far

  4. What is the X in “(+X)”? • This depends on the composition of the NLSP 0: • 0 = Bino  B(0  G) ≈ 80%  X = 2nd • 0 = [Bino  Wino]  X = lepton (Jovan) • 0 = [Bino  Higgsino]  X = b-jet(s) (Ofir) • 0 = [Bino  ???]  X = as little as possible (CMS: 3 jets with 30 GeV ET. • Other notes: • If Mcolored ≈ M0, additional activity can be very limited • If G (gravitino) coupling is weak, 0 can be metastable (non-pointing photons!) (Helen)

  5. Diphoton Analysis

  6. Basic Selection: • 2 with PT > 25 GeV • MET > 125 GeV

  7. Limits: Cast in 2D space of Mcolored vs MBino Note that since we don’t require jet activity we exclude all the way to the kinematic limit

  8. N.B. Comparison with CMS • In terms of the observed cross section limit, CMS and ATLAS are essentially identical (~25 fb-1), and: • These can be directly compared (same syst. error content) • P(e)CMS ≈ 0.1*P(e )ATLAS • CMS used slightly (~6%) more luminosity • CMS got slightly lucky (expected 1.5; observed 0) • Despite appearances (mass limit), ATLAS analysis appears superior per fb-1 In addition, ATLAS did not optimize for 1 fb-1 (we used essentially the same analysis as for 0.036 fb-1) We need to optimize; should result in favorable analysis relative to CMS

  9. Diphoton Analysis: Next Steps • First things first: we need to explore (clean up?) MET variables for events with high PT photons. We are currently using our fall-back, LocHadTopo. From Jason: • Not all of our recovered photons are treated correctly by the MET reconstruction, and we have some anecdotal evidence from our high-MET candidates that this is worse in high-pT photon events. Probably this is because of the straight scaling EM->hadronic JES; this makes the size of the (wrongly applied) correction larger for the high-pT photons. • This will have to be explored at AOD stage and brought forward (officially) into the D3PDs

  10. Diphoton Analysis: Next Steps • Next: Revisit backgrounds • QCD background is low (and consistent with CMS), but control samples may have significant EW contribution • EW (intrinsic MET): 1 fb-1 analysis supports e fakes as dominant contribution. Can we reduce w/out paying huge price in efficiency (as CMS apparently did)? • We have had ideas about this for a long time but to the present have been to pressed to explore them • MC study to better understand sources • Separate treatment of converted/unconverted • Use un-assigned pixel hits to eliminate brems

  11. Diphoton Analysis: A Few More Points • Include CMS-like `3D’ grid (MBino, Mgluino, Msquark) • Reoptimize • MET cut • Isolation • Photon PT • Other kinematic variables (, M, MET sig., etc.) • Think a bit harder about beam/halo background • Exploit initial state radiation (reference…) • Other things…? • So, there’s plenty to be done for the full 2011 dataset.

  12. Single Photon Analysis

  13. For now, interested groups are • Universidad Nacional de La Plata • UC Santa Cruz • Enabled by following triggers: • EF_g40_loose_xe45_medium_noMu ( EF_g40_loose_xe55_medium_noMu?) • g80_loose ( g100_loose?) • Basic questions: Analysis will be  + MET + X. • How little `X’ can we get away with? • What will we use to motivate/optimize search? • How will we constrain backgrounds? • Trigger MET treshold • Relative size of QCD control sample Much to be thought about.

  14. BACKUP SLIDES

  15. via gravity (mSUGRA) via gauge mediation (GMSB) At low energies, most scenarios with similar spectra… SUSY Broken in nature (mSUGRA) (GMSB) …but possible different phenomenologies at colliders.

  16. Experimental Signature Trigger: • EF_g40_loose_xe45_medium_noMu/EF_g40_loose_xe55_medium_noMu triggers? • g80_loose g100_loose (5. 1033 ) ? Selection: - |η| range, Photon pT , Photon quality :Tight?, Etcone (Calo isolation) vs Ptcone (track isolation)? MET definition, i.e. MET_RefFinal? ( Currently use LocHadTopo) number of Jets? Efficiencies: - Follow photon efficiency task force! - MET: Bruce please add….. Background: data driven methods • QCD: Prompt photon (direct / fragmentation) follow SM analysis • W, Z ttbar…

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