Search for the $b\bar{b}$ decay of the Standard Model Higgs boson in associated $(W/Z)H$ production with the ATLAS detector

TL;DR

This paper reports a search for the Higgs boson decaying into bottom quarks in association with W/Z bosons using ATLAS data, finding a modest excess over background consistent with the Standard Model.

Contribution

First search using full Run 1 ATLAS data for Higgs to bottom quarks in associated production, with a validation measurement of Z to bottom quarks.

Findings

Observed signal ratio μ = 0.52 ± 0.32 (stat.) ± 0.24 (syst.)

Significance of 1.4σ for Higgs signal

Validation measurement yields a ratio of 0.74 ± 0.09 (stat.) ± 0.14 (syst.)

Abstract

A search for the $b\bar{b}$ decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used from $pp$ collisions at $\sqrt{s}=7$ and 8 TeV are 4.7 and 20.3 fb$^{-1}$, respectively. The processes considered are associated $(W/Z)H$ production, where $W\to e\nu/\mu\nu$, $Z\to ee/\mu\mu$ and $Z\to\nu\nu$. The observed (expected) deviation from the background-only hypothesis corresponds to a significance of 1.4 (2.6) standard deviations and the ratio of the measured signal yield to the Standard Model expectation is found to be $\mu = 0.52 \pm 0.32 \mathrm{(stat.)} \pm 0.24 \mathrm{(syst.)}$ for a Higgs boson mass of 125.36 GeV. The analysis procedure is validated by a measurement of the yield of $(W/Z)Z$ production with $Z\to b\bar{b}$ in the same final states as for the Higgs boson search, from which the ratio of the observed signal yield to the Standard Model expectation is found to be $0.74 \pm 0.09 \mathrm{(stat.)} \pm 0.14 \mathrm{(syst.)}$.