Abstract
Results of a search for new particles decaying into eight or more jets and moderate missing transverse momentum are presented. The analysis uses 139 fb−1 of proton-proton collision data at sqrt{s} = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. The selection rejects events containing isolated electrons or muons, and makes requirements according to the number of b-tagged jets and the scalar sum of masses of large-radius jets. The search extends previous analyses both in using a larger dataset and by employing improved jet and missing transverse momentum reconstruction methods which more cleanly separate signal from background processes. No evidence for physics beyond the Standard Model is found. The results are interpreted in the context of supersymmetry-inspired simplified models, significantly extending the limits on the gluino mass in those models. In particular, limits on the gluino mass are set at 2 TeV when the lightest neutralino is nearly massless in a model assuming a two-step cascade decay via the lightest chargino and second-lightest neutralino.
Highlights
Background estimationSignal region SR-8ij50-0ib-MJ500 Nj5e0t ≥8Nj8e0t — Nb-jet — MJΣ [GeV] ≥500SR-9ij50-0ib-MJ340 ≥9 — — ≥340SR-10ij50-0ib-MJ340 ≥10 — —SR-10ij50-0ib-MJ500 ≥10 — — ≥500SR-10ij50-1ib-MJ500 ≥10 — ≥1 SR-11ij50 ≥11 — —
The current analysis extends those previous studies by including the complete Run-2 LHC dataset, by using an optimised selection tailored to the increased integrated luminosity, and by incorporating several improved analysis methods which further increase sensitivity
To account for uncertainties from the parton shower modelling and generator choice, the nominal sample is compared to a sample generated with Powheg-Box interfaced to Herwig 7 [60] using the H7UE tune [61] and the MMHT2014 leading order (LO) parton distribution functions (PDFs) set [62], as well as samples generated with MadGraph5 aMC@next-to-leading order (NLO) interfaced to Pythia 8
Summary
The ATLAS detector [10] is a multipurpose particle detector with a nearly 4π coverage in solid angle. It consists of an inner tracking detector (ID) surrounded by a thin superconducting solenoid providing a 2 T axial magnetic field, electromagnetic (EM) and hadronic. The ATLAS detector [10] is a multipurpose particle detector with a nearly 4π coverage in solid angle.. The ATLAS detector [10] is a multipurpose particle detector with a nearly 4π coverage in solid angle.1 It consists of an inner tracking detector (ID) surrounded by a thin superconducting solenoid providing a 2 T axial magnetic field, electromagnetic (EM) and hadronic. The inner tracking detector covers the pseudorapidity range |η| < 2.5. It consists of silicon pixel, silicon microstrip, and transition radiation tracking detectors. The muon spectrometer surrounds the calorimeters and is based on three large air-core toroidal superconducting magnets with eight coils each. The muon spectrometer includes a system of precision tracking chambers and fast detectors for triggering. This is followed by a software-based trigger that reduces the accepted event rate to 1 kHz on average
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