susy with photons and met: introduction and thoughts about diphoton and single photon analyses
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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 - PowerPoint PPT PresentationTRANSCRIPT
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SUSY with Photons and MET: Introduction and thoughts about
Diphoton and Single Photon AnalysesAnnecyDESY/University of HamburgLiverpool UniversityTokyo TechUniversity of California Santa CruzUniversidad Nacional de La PlataUniversity of WisconsinWeizmann Institute
Bruce Schumm12 Sept 2011
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General Intro
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Photon processes in SUSY
mSUGRA
• LSP: lightest neutralino• NLSP: 2nd neutralino• production: 1-loop
GMSB
• LSP: gravitino ( massless)
• NLSP: lightest neutralino• production: tree level
Collider phenomenology depends on nature of LSPs
Signature: + MET (+ X)
This group’s focus so far
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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 ≈ M0, additional activity can be very limited
• If G (gravitino) coupling is weak, 0 can be metastable (non-pointing photons!) (Helen)
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Diphoton Analysis
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Basic Selection: • 2 with PT > 25 GeV• MET > 125 GeV
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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
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N.B. Comparison with CMSIn 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
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Diphoton Analysis: Next StepsFirst 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
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Diphoton Analysis: Next StepsNext: 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
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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.
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Single Photon Analysis
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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.
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BACKUP SLIDES
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SUSY- Broken in nature
via gravity (mSUGRA)
via gauge mediation (GMSB)
At low energies, most scenarios with similar spectra…
…but possible different phenomenologies at colliders.
(mSUGRA) (GMSB)
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Experimental SignatureTrigger:- 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…