Measurement of the H→ γγ and H→ ZZ^∗→ 4 ℓ cross-sections in pp collisions at √s = 13.6 TeV with the ATLAS detector

The inclusive Higgs boson production cross-section is measured in the di-photon and the ZZ^∗→ 4 ℓ decay channels using 31.4 and 29.0 fb ^-1 of pp collision data respectively, collected with the ATLAS detector at a centre-of-mass energy of √s = 13.6 TeV . To reduce the model dependence, the measurement in each channel is restricted to a particle-level phase space that closely matches the channel’s detector-level kinematic selection, and it is corrected for detector effects. These measured fiducial cross-sections are σ_{fid , γ γ} = 76_-13⁺¹⁴ fb, and σ_{fid , 4 ℓ} = 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(pp→H)=67_-11⁺¹² pb and 46 ± 12 pb at 13.6 TeV from the di-photon and ZZ^∗→ 4 ℓ measurements respectively. The two measurements are combined into a total cross-section measurement of σ(pp→ H) = 58.2 ± 8.7 pb, to be compared with the Standard Model prediction of σ(pp→ H) _SM = 59.9 ± 2.6 pb.