Photon(s) + MET Analyses

Bruce Schumm

UC Santa Cruz / SCIPP

16 April 2013

ATLAS SUSY Workshop

Amsterdam, NE

Motivation: GMSB and the Bino NLSP

• GMSB breaks SUSY via intermediate-scale messenger interactions

• Naturally protects SM flavor symmetry

• LSP is gravitino

• Over much of parameter space NLSP is short-lived Bino

• B(bino G) cos2W 78%

Diphoton + ETmiss signature

Photon + Njets + ETmiss signature

bino cos2W

“Minimal” GMSB

Prior Analysis: Diphoton + MET

A: Strong production, heavy binoB: Strong production, light binoC: Electroweak production

Strong production

EW production

For strong production, high total-energy cut gives~background-free analysis

8 TeV Analysis: Diphoton + MET

“SPS8” Trajectory

For 2012 (8 TeV) Data:

Replace “constrained” SPS8 grid with wino/bino grid

Bino = 10

Wino = degenerate triplet 1 and 2

0

Production through 1 2

0 and 1+ 1

-

Signal region optimization points

Low-mass, high-mass bino for Strong and EW production

Resulting signal regions

“Model-independent” selection MET cut for which QCD, EW background are about the same.

Issue for Photon(s) + MET Analyses: What MET?

• Significant changes for p1328 relative to p1181• Use gamma-gamma MC as proxy for signal (can look at high MET)

• EG10NoTauPhotonLoose designed for photon analyses; performs worse in p1328

• “Vanilla” MetRefFinal does well

Control samples for MetRefFinal

“g” is control photon (loose but not tight); can be isolated or not

“t” is isolated tight photon

“QCDtg” is nominal diphoton control sample

Good agreement w/ signal MET, especially QCDtg

Challenges: “Irreducible” W Background

• Sizeable for EW production and “model independent” selections• Constrain with data looking at (e,) events

Expected signal(MC)

50 < MET < 125

125 < MET < 250

125 < MET < 250

Expect: ~1.5

Observe: 0

Constrains K-factor (currently assumed to be 33)

CMS diphoton+MET with 4 fb-1 at 8 TeV

CMS diphoton analysis:

• Employs no “overall energy scale” observable (HT, Meff)

• Single analysis similar to ATLAS “MIS” signal region

• Look at strong production only

Single Photon + MET Analysis

Motivation: Diphoton analysis may not be sensitive if

• Neutralino is not NLSP (no photons; not for this session!)• Neutralino is the NLSP but is not purely bino

GMSB Neutralino NLSP Phenomenology

• Bino-like diphoton final state• Wino-like admixture photon + lepton• Higgsino-like admixture, <0 photon + bjets• Higgsino-like admixture, >0 photon + jets

Single Photon + MET analysis covers this final, missing signature

CMS single- analysis

• Photon ET > 80 GeV

• 2 jets with pT > 30 GeV

• HT > 450 GeV

• MET in bins, but sensitivity arises for MET > 250

• Set limit of mgluino > 1125 GeV for bino-like neutralino (4 fb-1 at 8 TeV)

Single-Photon + MET Signal Regions

• Minimize model dependence by minimizing Njet requirement

• RT2 is fraction of total visible energy in two leading jets

Photon + MET Challenges / Next Steps

Devising grid was significant development (tune gluino, neutralino BFs and lifetimes) but is now being submitted for generation.

Next steps: understand backgrounds challenges, e.g.

Conclusions and Outlook

For 8 TeV data, significant new model space has been introduced

• Weak production (decoupled strong partners) limits with diphoton analysis (bino-like neutralino)

• GMSB scenario with photon + jet signature

Plan is summary paper with all four photon(s) + MET analysis, covering full range of neutralino NLSP possibilities, plus electroweak production for bino- and wino-like NLSP

Distinction between pointing, non-pointing signatures is somewhat arbitrary and artificial Combine into unified analysis for 2015 data?