Search for charged Higgs bosons produced in association with a top quark and decaying via $H^{\pm} \rightarrow \tau\nu$ using $pp$ collision data recorded at $\sqrt{s} = 13$ TeV by the ATLAS detector

TL;DR

This paper reports a search for charged Higgs bosons produced with a top quark decaying to tau and neutrino, setting upper limits on production cross section for masses between 200 and 2000 GeV using 13 TeV LHC data.

Contribution

First search for charged Higgs bosons in association with a top quark decaying to tau neutrino at 13 TeV, providing the most stringent limits to date.

Findings

No significant excess over Standard Model background.

Set upper limits on production cross section between 1.9 pb and 15 fb.

Excluded parameter space for charged Higgs masses up to 2000 GeV.

Abstract

Charged Higgs bosons produced in association with a single top quark and decaying via $H^{\pm} \rightarrow \tau\nu$ are searched for with the ATLAS experiment at the LHC, using proton-proton collision data at $\sqrt{s} = 13$ TeV corresponding to an integrated luminosity of 3.2 $\mathrm{fb}^{-1}$. The final state is characterised by the presence of a hadronic $\tau$ decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to $95\%$ confidence-level upper limits on the production cross section times branching fraction, $\sigma(pp \rightarrow [b]t H^{\pm}) \times \mbox{BR}(H^{\pm} \rightarrow \tau\nu)$, between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. The exclusion limits for this search surpass those obtained with the proton-proton collision data recorded at $\sqrt{s} = 8$ TeV.