Search for new phenomena in final states with large jet multiplicities and missing transverse momentum using s
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Springer
Received: August 14, 2020 Accepted: September 9, 2020 Published: October 12, 2020
The ATLAS collaboration E-mail: [email protected] 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 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. Keywords: Hadron-Hadron scattering (experiments) ArXiv ePrint: 2008.06032
Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP10(2020)062
JHEP10(2020)062
Search for new phenomena in final states with large jet multiplicities and missing transverse momentum √ using s = 13 TeV proton-proton collisions recorded by ATLAS in Run 2 of the LHC
Contents 1
2 ATLAS detector
2
3 Datasets 3.1 Data 3.2 Monte Carlo simulations
3 3 4
4 Reconstruction and particle identification
7
5 Event selection
9
6 Background estimation 6.1 Multijet background 6.2 Leptonic backgrounds 6.3 Background normalisation corrections 6.4 Systematic uncertainties
11 13 16 17 18
7 Results and interpretation
23
8 Conclusion
28
The ATLAS collaboration
36
1
Introduction
The Large Hadron Collider [1] (LHC) has produced a large dataset of proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV enabling searches for new heavy particles predicted by theories such as supersymmetry (SUSY) [2–7]. Evidence for SUSY models may be sought through searches for the production of these heavy particles (such as gluinos) decaying, often via extended cascades, into lighter ones. If the lightest of these interacts only weakly and is stable then it can be an ideal dark-matter candidate. In R-parity-conserving (RPC) [8] SUSY models, the presence of a stable lightest supersymmetric particle (LSP) often leads to final states with significant missing transverse miss ), often accompanied by a large number of jets. Large jet multiplicities momentum (ET would also occur in events in which gluinos decay via R-parity-violating (RPV) [9] couplings on short (. ns) timescales. In this case the LSPs decay within the detector v
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