Search for a light charged Higgs boson in the H$^\pm$ $\to $ cs channel in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports a search for a light charged Higgs boson decaying into charm and strange quarks in proton-proton collisions at 13 TeV, using CMS data, setting upper limits on the decay branching fraction.

Contribution

First search for a low-mass charged Higgs in the cs decay channel in top quark pair events at 13 TeV with charm tagging.

Findings

No significant excess observed in the dijet mass distribution.

Upper limits on top quark decay branching fraction range from 1.68% to 0.25%.

Analysis enhances sensitivity with charm jet tagging.

Abstract

A search is conducted for a low-mass charged Higgs boson produced in a top quark decay and subsequently decaying into a charm and a strange quark. The data sample was recorded in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS experiment at the LHC and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The search is performed in the process of top quark pair production, where one top quark decays to a bottom quark and a charged Higgs boson, and the other to a bottom quark and a W boson. With the W boson decaying to a charged lepton (electron or muon) and a neutrino, the final state comprises an isolated lepton, missing transverse momentum, and at least four jets, of which two are tagged as b jets. To enhance the search sensitivity, one of the jets originating from the charged Higgs boson is required to satisfy a charm tagging selection. No significant excess beyond standard model predictions is found in the dijet invariant mass distribution. An upper limit in the range 1.68-0.25% is set on the branching fraction of the top quark decay to the charged Higgs boson and bottom quark for a charged Higgs boson mass between 80 and 160 GeV.