Search for new long-lived particles at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports a search for long-lived particles at 13 TeV using CMS data, setting new limits on particle masses and decay lengths, and employing specialized triggers to identify displaced jet signatures.

Contribution

It introduces a novel analysis using topological triggers and displaced jet multiplicity to search for long-lived particles, extending sensitivity to higher masses and longer decay lengths.

Findings

Excluded cross sections above 2.5 fb for certain decay lengths and masses.

Set the most stringent mass limits for top squarks with decay lengths over 3 mm.

Achieved sensitivity to decay lengths between 1 and 1000 mm.

Abstract

A search for long-lived particles was performed with data corresponding to an integrated luminosity of 2.6 fb$^{-1}$ collected at a center-of-mass energy of 13 TeV by the CMS experiment in 2015. The analysis exploits two customized topological trigger algorithms, and uses the multiplicity of displaced jets to search for the presence of a signal decay occurring at distances between 1 and 1000 mm. The results can be interpreted in a variety of different models. For pair-produced long-lived particles decaying to two b quarks and two leptons with equal decay rates between lepton flavors, cross sections larger than 2.5 fb are excluded for proper decay lengths between 70-100 mm for a long-lived particle mass of 1130 GeV at 95% confidence. For a specific model of pair-produced, long-lived top squarks with R-parity violating decays to a b quark and a lepton, masses below 550-1130 GeV are excluded at 95% confidence for equal branching fractions between lepton flavors, depending on the squark decay length. This mass bound is the most stringent to date for top squark proper decay lengths greater than 3 mm.