Search for heavy charged long-lived particles in proton-proton collisions at $\sqrt{s}=13$ TeV using an ionisation measurement with the ATLAS detector

Abstract

This Letter presents a search for heavy charged long-lived particles produced in proton-proton collisions at $\sqrt{s}=13$ TeV at the LHC using a data sample corresponding to an integrated luminosity of 36.1 fb${}^{-1}$ collected by the ATLAS experiment in 2015 and 2016. These particles are expected to travel with a velocity significantly below the speed of light, and therefore have a specific ionisation higher than any high-momentum Standard Model particle of unit charge. The pixel subsystem of the ATLAS detector is used in this search to measure the ionisation energy loss of all reconstructed charged particles which traverse the pixel detector. Results are interpreted assuming the pair production of $R$-hadrons as composite colourless states of a long-lived gluino and Standard Model partons. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on $R$-hadron production cross-sections and gluino masses are set, assuming the gluino always decays in two quarks and a stable neutralino. $R$-hadrons with lifetimes above 1.0 ns are excluded at the 95% confidence level, with lower limits on the gluino mass ranging between 1290 GeV and 2060 GeV. In the case of stable $R$-hadrons, the lower limit on the gluino mass at the 95% confidence level is 1890 GeV.

36 pages in total, author list starting page 20, 6 figures, 2 tables, final version published in Physics Letters B. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2016-31/

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• Reinterpretation of LHC Results for New Physics: Status and Recommendations after Run 2
• Search for top squark production in fully-hadronic final states in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• GUT Physics in the era of the LHC
• Implications of Feebly Interacting Dark Sector on Neutron Star Properties and Constraints from GW170817
• Non-Decoupling New Particles
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• GUT-inspired MSSM in light of muon $g-2$ and LHC results at $\sqrt{s}=13$ TeV
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• Search for heavy long-lived multi-charged particles in the full LHC Run 2 $pp$ collision data at $\sqrt{s}$ = 13 TeV using the ATLAS detector
• Freeze-in and Freeze-out of Dark Matter with Charged Long-lived Partners
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• The Smallest SU($N$) Hadrons
• Dark Unification: a UV-complete Theory of Asymmetric Dark Matter
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