Speaker
Description
A search for the Higgs boson decay to a $Z$ boson and a photon in the $\ell\ell\gamma$ ($\ell = e, \mu$) final state is performed using $pp$ collisions at $\sqrt{s} = 13.6$TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022--2024, corresponding to an integrated luminosity of 165fb$^{-1}$. The signal yield, normalised to the Standard Model prediction, is measured to be $\mu = 0.9^{+0.7}_{-0.6}$, compatible with the expected value of $\mu = 1.0 \pm 0.7$. This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations under the background-only hypothesis. This result is combined with that of a similar search performed with 140fb$^{-1}$ of $\sqrt{s} = 13$TeV $pp$ collisions to provide the best expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of $\mu = 1.3^{+0.6}_{-0.5}$ ($\mu = 1.0^{+0.6}_{-0.5}$), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation.
