Inclusive susy reach of cms during early lhc running in the jets met n leptons topology
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Inclusive SUSY Reach of CMS during Early LHC Running in the Jets + MET + N Leptons topology. Bobby Scurlock Darin Acosta Richard Cavanaugh. University of Florida. Overview. Motivation Phase 1 : Prelude Establish “full-chain” Verify CMS Note 98-073 with “full-chain”

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Inclusive SUSY Reach of CMS during Early LHC Running in the Jets + MET + N Leptons topology

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Inclusive susy reach of cms during early lhc running in the jets met n leptons topology

Inclusive SUSY Reach of CMS during Early LHC Running in the Jets + MET + N Leptons topology

Bobby Scurlock

Darin Acosta

Richard Cavanaugh

University of Florida



  • Motivation

  • Phase 1 : Prelude

    • Establish “full-chain”

    • Verify CMS Note 98-073 with “full-chain”

  • Phase 2 : Main emphasis

    • Study systematic effects on reach

    • Establish reach scenarios

  • Phase 3

    • Write contributions for Physics TDR

    • Defend PhD !

Our interest

Our Interest

  • Extend earlier Florida JetMET BSM analysis efforts from CDF to CMS

  • Collaborate with other CMS members:

    • Florida Colleagues on SS 2μ Inclusive SUSY Reach Analysis:

      • A.Drozdetski, Y.Pakhotin, P.Bartalini, D.Acosta, G.Mitselmakher

    • JetMET Group:

      • Haifeng Pi, Arno Heister, Rob Harris, et al.

    • UF SUSY/BSM Theorists:

      • P. Ramond, R. Field, and K. Matchev

  • Focus on early (~10 fb-1) LHC physics

    • Establish realistic reach expectations

      • Study systematic effects

      • Consider “What if…” scenarios

    • Probe quasi-model-independent reaches

Earlier cms work

Earlier CMS Work

Abdullin & Charles (CMS Note 98-073)

  • Used Fast Sim. (CMSJET) of CMS detector

  • Established reasonable criteria for signal selection & background rejection, and sensible expectations for signal & background distributions

  • Studied some simple systematics

    • Signal & Background variations

    • Pile-up effects

  • QCD background was (remains) a serious challenge


    Gives idea of Level-1 Trigger and HLT requirements for good efficiency for SUSY events over several representative points in mSUGRA space

What if

What if…

…we assume a well understood detector?

  • 0 leptons + Jets + MET has most significant reach

…we assume, e.g., that calorimeter responses are not well understood?

  • Would n muons + Jets + MET be more significant?

  • If so, at what level of jet energy scale uncertainty?

Abdullin & Charles

(CMS Note 98-073)

Phase 1 analysis set up

Establish “full-chain” analysis




Develop RootMaker

Defining our own currently

Investigating JetMET ntuple

Run on Digis (baseline)

Run on DSTs (when stable)

“Full-chain” important for systematic studies !

Modify physics process

Perturb detector response

Change reconstruction







Phase 1 : Analysis set-up





MCinfo,G4 Vtx, Tk



MC generator



Analysis or Calibration








RecColl, Digis




RecColl, Digis





Phase 1 digi datasets signal

Phase 1 : Digi Datasets - Signal

Need more signal !

Phase 1 digi datasets ew background

Phase-1 : Digi Datasets – EW Background

Z+jets lagging a bit !

Phase 1 digi datasets qcd background

Phase-1 : Digi Datasets – QCD Background

Need inclusive TTbar !

Need more high PT QCD !

Phase 1 digi datasets higher order ew background

Phase 1 : Digi Datasets - Higher order EW Background

Location of inclusive

WW, ZW ?

Phase 1 confirm abdullin charles

Phase 1 : Confirm Abdullin & Charles

  • Examine distributions after full simulation:

    • Jet multiplicity, ET, ETMiss, Δφ(ETjet1, ETMiss), etc…

  • Simple optimised cut set based on significance = Ns / √(Ns+Nb)

    • Try/use initial selection criteria from Abdullin & Charles

  • Produce preliminary expected reach in m0 vs m1/2 plane

    • 10 fb-1

    • 100 fb-1

  • Ultimately, would like to limit number of cut sets used, by carving out regions in mSUGRA space rather than optimizing cuts for each particular point – this reduces systematics…

Phase 2 systematics the main emphasis of this work

N = (εSσS + εBσB) L

Estimate uncertainties in cross-section σB

Treat QCD differently from EW


Guess at uncertainties in Luminosity L

Estimate uncertainties in efficiencies εS , εB

MC statistics

Detector Effects

Reconstruction Effects





Examine uncertainties on backgrounds in control regions

Phase 2 : Systematics: The main emphasis of this work

Phase 2 systematics triggers

Phase 2 : Systematics – Triggers

  • Jet Corrections at L1?

  • Trigger Efficiencies:

    • Jet+ETMiss

    • Muons

    • Electrons

    • Inclusive SUSY

Phase 2 systematics reconstruction of physics objects

Phase 2 : Systematics – Reconstruction of Physics Objects

  • Jets:

    • E/HCAL Calibration

    • Tracking Uncertainties

    • ET vs. h

  • ETMiss:

    • Calibration

    • Fake Rates

    • Azimuthal Isolation

  • Muons

    • B-Field

    • Detector Alignment

    • Brem

  • Electrons

    • B-Field

    • ECAL Calibration

    • Brem

Phase 2 significance estimator

Phase 2 : Significance Estimator

  • Estimate reach at 95% CL using likelihood

  • Include systematic effects via convolution

Likelihood for SUSY Signal hypothesis, given Experimental Data and assuming knowledge of Standard Model Background

Systematic Gaussian PDFs

Statistical Poisson PDF

Phase 2 quasi model independent studies

Phase 2 : Quasi-model-independent studies

  • “What if…” mSUGRA is not the SUSY breaking model realised in Nature?

  • Investigate more model independent approaches for setting reaches

    • Physical squark and gluino masses

    • Cross-section x BRs

    • Validate against several different SUSY models at generator level

Phase 2 famos

Potentially very useful for:

mSUGRA parameter sweeps

Estimates of systematic effects which are otherwise to costly

Investigate Distributions of Physics Objects:


ET of leading jet, ET of next leading jet, MET of event, Jet multiplicity, etc…


PT of leading muon, PT of next leading muon, Muon isolation, etc…


ET of leading electron, ET of next leading electron, Electron isolation, etc...

Phase 2 : FAMOS

Synergy with inclusive ss 2 susy reach

Synergy with Inclusive SS 2μ SUSY Reach

  • Authors:

    • Alexei Drozdetski (see today’s talk), Yuriy Pakhotin, Paolo Bartalini, Darin Acosta, Guenakh Mitselmakher

  • Many systematics are the same (or similar) for both analyses

    • Division of labor

    • Agree on a common Root Tree

  • Etc…



  • Interested in conducting inclusive SUSY search in the Jets + MET + Leptons topology to establish realistic reach expectations

  • In process of mastering analysis chain and crating analysis tools

  • Will conduct sanity checks against previous studies

  • Consider various “What if …” scenarios, and systematic effects

  • Would like to evolve to a model independent study

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