Measurement of the Higgs boson mass with $H \rightarrow \gamma\gamma$ decays in 140 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector

The mass of the Higgs boson is measured in the $H\to\gamma\gamma$ decay channel, exploiting the high resolution of the invariant mass of photon pairs reconstructed from the decays of Higgs bosons produced in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=13$ TeV. The dataset was collected between 2015 and 2018 by the ATLAS detector and corresponds to an integrated luminosity of 140 fb$^{-1}$. The measured value of the Higgs boson mass is $125.17 \pm 0.11~\mathrm{(stat.)} \pm 0.09~\mathrm{(syst.)}$ GeV and is based on an improved energy scale calibration for photons whose impact on the measurement is about four times smaller than in the previous publication. A combination with the corresponding measurement using 7 and 8 TeV $pp$ collision ATLAS data results in a Higgs boson mass measurement of $125.22 \pm 0.11~\mathrm{(stat.)} \pm 0.09~\mathrm{(syst.)}$ GeV. With a relative uncertainty of 1.1 per mille, this is currently the most precise measurement of the mass of the Higgs boson from a single decay channel.