A Search for Neutral Long-Lived Particles Decaying into Displaced Jets in the ATLAS Calorimeter in Proton-Proton Collisions at the LHC

Abstract

A search for neutral long-lived particles (LLPs) decaying in the ATLAS hadronic calorimeter using 140 fb^-1 of proton proton collisions at √s = 13 TeV delivered by the LHC is presented. The analysis targets pair-produced LLPs where at least one LLP is produced with sufficiently low boost that its decay products can be resolved as separate jets. No excesses of events relative to the background predictions are observed. Higgs boson branching fractions to pairs of hadronically decaying neutral LLPs larger than 1% are excluded at 95% confidence level for proper decay lengths in the range of 30 cm to 4.5 m depending on the LLP mass, a factor of three improvement on previous searches in the hadronic calorimeter.