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 AnalysesAnnecyDESY/University of HamburgLiverpool UniversityTokyo TechUniversity of California Santa CruzUniversidad Nacional de La PlataUniversity of WisconsinWeizmann Institute

Bruce Schumm12 Sept 2011

General Intro

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

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)

Diphoton Analysis

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

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

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

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

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

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.

Single Photon Analysis

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.

BACKUP SLIDES

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)

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…