Search for long-lived particles using displaced jets in proton-proton collisions at $\sqrt{s} = $ 13 TeV

TL;DR

This paper reports a comprehensive search for long-lived particles decaying into displaced jets in proton-proton collisions at 13 TeV, setting new limits on various models including supersymmetry and Higgs decays.

Contribution

It combines multiple datasets to improve sensitivity and provides the most stringent limits to date on long-lived particle models with displaced jets.

Findings

Excluded long-lived particles with masses up to 2600 GeV for gluinos.

Set limits on branching fractions of Higgs decays to long-lived scalars.

Achieved the most stringent constraints on long-lived gluinos and top squarks.

Abstract

An inclusive search is presented for long-lived particles using displaced jets. The search uses a data sample collected with the CMS detector at the CERN LHC in 2017 and 2018, from proton-proton collisions at a center-of-mass energy of 13 TeV. The results of this search are combined with those of a previous search using a data sample collected with the CMS detector in 2016, yielding a total integrated luminosity of 132 fb$^{-1}$. The analysis searches for the distinctive topology of displaced tracks and displaced vertices associated with a dijet system. For a simplified model, where pair-produced long-lived neutral particles decay into quark-antiquark pairs, pair production cross sections larger than 0.07 fb are excluded at 95% confidence level (CL) for long-lived particle masses larger than 500 GeV and mean proper decay lengths between 2 and 250 mm. For a model where the standard model-like Higgs boson decays to two long-lived scalar particles that each decays to a quark-antiquark pair, branching fractions larger than 1% are excluded at 95% CL for mean proper decay lengths between 1 mm and 340 mm. A group of supersymmetric models with pair-produced long-lived gluinos or top squarks decaying into various final-state topologies containing displaced jets is also tested. Gluino masses up to 2500 GeV and top squark masses up to 1600 GeV are excluded at 95% CL for mean proper decay lengths between 3 and 300 mm. The highest lower bounds on mass reach 2600 GeV for long-lived gluinos and 1800 GeV for long-lived top squarks. These are the most stringent limits to date on these models.