Search for squarks and gluinos with the ATLAS
detector in final states with jets and missing
transverse momentum in Run2
Yuta Sano, D1, N-lab, Nagoya University
2. Analysis strategy
1. Introduction
The recent increase in the center of mass energy ofthe proton-proton collisions gives a unique
opportunity to extend the sensitivity to production ofsupersymmetric particles at the Large Hadron
Collider. The production cross section of 1.5 TeV
gluinos for √s = 13 TeV is 50 times larger than thatfor √s = 8 TeV. Our focus is on gluinos and squarks.
Final state:• 0 lepton + 2 – 6 jets + missing transverse energy• This 0-lepton channel is one of the promising
analyses for SUSY discovery exceeding theRun-1 exclusion just with the early Run-2 dataset.
Covered signatures:• 2j for squark pairs, 4j for gluino pairs, ≥ 5j for long
decay chains

The analysis is based on 13.3 fb-1 of ATLAS data at √s =13 TeV. Signal Regions (SRs) to enhance each targeted
signal are defined.
Main discriminating variables:• Number of jets, Effective mass (meff, the scalar sum oftransverse momenta of the jets and missing transverseenergy)
The other variables:• ETmiss/meff (ETmiss: missing transverse energy), ΔΦ(ji, ETmiss)(Angular between jets and ETmiss) to reduce QCDbackgrounds• Aplanarity to distinguish spherical events from planar orlinear events.
Definition of one of the SRs, SR4j-2200:• Number of jets > 4, meff > 2200 GeV• Aplanarity > 0.04, ETmiss/meff > 0.2, ΔΦ(ji, ETmiss) > 0.4
Background estimation:• W+jets, ttbar, Z+jets, QCD: normalization fitted
simultaneously to data in specific CR• Diboson: estimated entirely using MC simulation

3. Results using 13.3 fb-1 data (ATLAS-CONF-2016-078, http://cds.cern.ch/record/2206252)
Observed vs predicted event yields

Interpretation

No excess above the Standard Model backgroundexpectation was observed in any of the SRs

Squark masses below 1.35 TeV and gluino masses
below 1.86 TeV are excluded at the 95% confidence level

4. Outlook for the analysis with more data

For next update with Run2 full dataset, we areinvestigating new b-veto/b-tag SRs in order tocover various models more widely e.g. pMSSM.
Reference : ATLAS-CONF-2016-078

Data 25 events, MC Total 21.4 events in CR3L (Diboson:14.90, the others:6.47)

CR3L for SR2j-0800

ATLAS Internal

102

Data 2015 and 2016

s=13 TeV, 36.5 fb-1

SM Total

10

the others
Diboson1

10<1

Data / MCAs one of the improvements, we developed newcontrol region for diboson background, which waspredicted only with MC simulation anduncertainties are very large (50%) due to PDF,renormalization, factorization and resummation
scale uncertainties. The uncertainty may be
reduced using final state with three leptons (WZ→ lvll) considered as CR for diboson background.

events / 200.0 GeV

We are currently updating the results with
2015+2016 dataset (40 fb-1) for this spring.

10<102500

1000

1500

2000

2500

7.5

3000

3500

meff(incl.) [GeV]

52.50500

1000

1500

2000

2500

3000

3500

meff(incl.) [GeV]

The uncertainty on thebackground estimate forSR2j-0800. Diboson events
has one of largest uncertainty.

Region of SR2j-0800 withthree leptons w/o cuts onvariables to reduce QCD
events. 40 fb-1 is used.