Abstract
A search for squarks and gluinos in final states containing high-$p_{\rm T}$ jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in $\sqrt{s}=8$ TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of $20.3 \mathrm{fb}^{-1}$. No significant excess above the Standard Model expectation is observed. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with $\tan\beta=30$, $A_0=-2m_0$ and $\mu> 0$, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector.
Highlights
Background estimationThe observed numbers of events in the control regions (CRs) for each SR are used to generate consistent SM background estimates for the SR via a likelihood fit [98]
Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino
When using the baseline POWHEG-BOX+PYTHIA top quark pair production sample, events are reweighted in bins of pT(tt) to match the top quark pair differential cross-section observed in ATLAS data [26, 27]
Summary
The ATLAS detector [24] is a multipurpose particle physics detector with a forwardbackward symmetric cylindrical geometry and nearly 4π coverage in solid angle. The detector features four superconducting magnet systems, which comprise a thin solenoid surrounding inner tracking detectors (covering |η| < 2.5) and, outside a calorimeter system, three large toroids supporting a muon spectrometer (covering |η| < 2.7, with trigger coverage in the region |η| < 2.4). The ATLAS detector [24] is a multipurpose particle physics detector with a forwardbackward symmetric cylindrical geometry and nearly 4π coverage in solid angle.. The detector features four superconducting magnet systems, which comprise a thin solenoid surrounding inner tracking detectors (covering |η| < 2.5) and, outside a calorimeter system, three large toroids supporting a muon spectrometer (covering |η| < 2.7, with trigger coverage in the region |η| < 2.4). The calorimeters are of particular importance to this analysis. In the pseudorapidity region |η| < 3.2, high-granularity liquid-argon (LAr) electromagnetic (EM) sampling calorimeters are used. An iron/scintillator-tile calorimeter provides hadronic coverage over |η| < 1.7. The end-cap and forward regions, spanning 1.5 < |η| < 4.9, are instrumented with LAr calorimeters for both EM and hadronic energy measurements
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