Search for exclusive Higgs and $Z$ boson decays to $\varphi \gamma$ and $\rho \gamma$ with the ATLAS detector

Abstract

A search for the exclusive decays of the Higgs and $Z$ bosons to a $\varphi$ or $\rho$ meson and a photon is performed with a $pp$ collision data sample corresponding to an integrated luminosity of up to 35.6 $f{b}^{-1}$ collected at $\sqrt{s}=13$ TeV with the ATLAS detector at the CERN Large Hadron Collider. These decays have been suggested as a probe of the Higgs boson couplings to light quarks. No significant excess of events is observed above the background, as expected from the Standard Model. Upper limits at 95$\%$ confidence level were obtained on the branching fractions of the Higgs boson decays to $\varphi \gamma$ and $\rho \gamma$ of $5.0\times 10^{-4}$ and $10.4\times 10^{-4}$, respectively. The corresponding 95$\%$ confidence level upper limits for the $Z$ boson decays are $0.7\times 10^{-6}$ and $4.0\times 10^{-6}$ for $\varphi \gamma$ and $\rho \gamma$, respectively.

36 pages in total, author list starting page 20, 5 figures, 3 tables, published in JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2016-13/