Search for b hadron decays to long-lived particles in the CMS endcap muon detectors

TL;DR

This paper reports a search for long-lived particles from b hadron decays in the CMS endcap muon detectors, setting new upper limits on certain decay branching fractions using 2018 LHC data.

Contribution

It introduces a novel search method for long-lived particles in the CMS muon system and provides the most stringent upper limits to date on specific B meson decay channels.

Findings

Set new upper limits on B to KΦ branching fractions

Constrained long-lived particle decay lengths from 1 to 500 cm

Enhanced sensitivity to long-lived particles in the CMS muon system

Abstract

A search for long-lived particles originating from the decay of b hadrons produced in proton-proton collisions with a center-of-mass energy of 13 TeV at the LHC is presented. The analysis is performed on a data set recorded in 2018, corresponding to an integrated luminosity of 41.6 fb$^{-1}$. Interactions of the long-lived particles in the CMS endcap muon system would create hadronic or electromagnetic showers, producing clusters of detector hits. Selected events contain at least one such high-multiplicity cluster in the muon endcaps and require the presence of a displaced muon. The most stringent upper limits to date on the branching fraction $\mathcal{B}$(B $\to$ K$\Phi$), where the long-lived particle $\Phi$ decays to a pair of hadrons, are obtained for $\Phi$ masses of 0.3$-$3.0 GeV and $\Phi$ mean proper decay lengths in the range of 1$-$500 cm.