Measurement of the H -> gamma gamma and H -> ZZ* -> 4 l cross-sections in pp collisions at sqrt(s) = 13.6 TeV with the ATLAS detector

The inclusive Higgs boson production cross-section is measured in the di-photon and the 𝑍 𝑍∗ → 4ℓ decay channels using 31.4 and 29.0 fb−1 of 𝑝 𝑝 collision data respectively, collected with the ATLAS detector at a centre-of-mass energy of sqrt(s) = 13.6 TeV. In order to reduce the model dependence, the measurement in each channel is restricted to a particle-level phase space that matches closely the channel’s detector-level kinematic selection, and it is corrected for detector effects. The measured so-called fiducial cross-sections are 𝜎fid,𝛾𝛾 = 76+14−13 fb, and 𝜎fid,4ℓ = 2.80±0.74 fb, in agreement with the corresponding Standard Model predictions of 67.6±3.7 fb and 3.67±0.19 fb. Assuming Standard Model acceptances and branching fractions for the two channels, the fiducial measurements are extrapolated to the full phase space yielding total cross-sections of 𝜎(𝑝 𝑝 → 𝐻) = 67+12−11 pb and 46 ± 12 pb at sqrt(s) = 13.6 TeV from the di-photon and 𝑍 𝑍∗ → 4ℓ measurements respectively. The two measurements are combined into a total cross-section measurement of 𝜎(𝑝 𝑝 → 𝐻) = 58.2 ± 8.7 pb, to be compared with the Standard Model prediction of 𝜎(𝑝 𝑝 → 𝐻)SM = 59.9 ± 2.6 pb.