Measurements of $WH$ and $ZH$ production with Higgs boson decays into bottom quarks and direct constraints on the charm Yukawa coupling in $13\,\mathrm{TeV}$ $pp$ collisions with the ATLAS detector

TL;DR

This paper reports measurements of Higgs boson production with W/Z bosons decaying into bottom and charm quarks, providing new constraints on the charm Yukawa coupling using 13 TeV proton-proton collision data from ATLAS.

Contribution

First measurement of associated Higgs production with W/Z bosons decaying into bottom and charm quarks at 13 TeV, setting limits on the charm Yukawa coupling and its ratio to bottom.

Findings

Observed (expected) significance of 5.3 (5.5) for WH with H→bb

Observed (expected) upper limit of 11.5 (10.6) times SM for H→cc

Constraint on charm coupling modifier: |κ_c| < 4.2 at 95% CL

Abstract

A study of the Higgs boson decaying into bottom quarks ($H \to b\bar{b}$) and charm quarks ($H \to c\bar{c}$) is performed, in the associated production channel of the Higgs boson with a $W$ or $Z$ boson, using $140\,\mathrm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s} = 13\,\mathrm{TeV}$ collected by the ATLAS detector. The individual production of $WH$ and $ZH$ with $H \to b\bar{b}$ is established with observed (expected) significances of $5.3$ ($5.5$) and $4.9$ ($5.6$) standard deviations, respectively. Differential cross-section measurements of the gauge boson transverse momentum within the simplified template cross-section framework are performed in a total of 13 kinematical fiducial regions. The search for the $H \to c\bar{c}$ decay yields an observed (expected) upper limit at 95\% confidence level of $11.5$ ($10.6$) times the Standard Model prediction. The results are also used to set constraints on the charm coupling modifier, resulting in $|\kappa_c| < 4.2$ at 95\% confidence level. Combining the $H \to b\bar{b}$ and $H \to c\bar{c}$ measurements constrains the absolute value of the ratio of Higgs-charm and Higgs-bottom coupling modifiers ($|\kappa_c/\kappa_b|$) to be less than $3.6$ at 95$\% $ confidence level.