Higgs cross section measurements at $\sqrt{s}=13~\text{TeV}$ using the ATLAS detector

A measurement of the Higgs boson fiducial cross section in the diphoton decay channel is presented using 36.1 fb$^{−1}$ data collected by the ATLAS detector with proton-proton collisions provided by the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. The fiducial volume is defined by kinematic and particle-level isolation requirements applied to the final state photons. A result of 55 ± 9 (stat.) ± 4 (syst.) fb is obtained. The statistical precision is approximately double that of the measurement at $\sqrt{s}$ = 8 TeV and probes production at higher partonic centre-of-mass energies. Several differential cross sections are presented in the fiducial phase space. These characterise the properties of Higgs production and decay in a minimally model dependent way. A measurement of the total Higgs boson cross section is presented using the same dataset and the combination of diphoton and four-lepton decay channels. A result of 57.0 $^{+6.0}_{-5.9}$ (stat.) $^{+4.0}_{−3.3}$ (syst.) pb is obtained. The fiducial acceptances and branching ratios are assumed to follow the Standard Model expectations. Four differential cross sections are presented using the combination of channels. The expected sensitivity of a differential cross section measurement in the diphoton channel is presented assuming the phase 2 upgrade of the electromagnetic calorimeter and a dataset of 3 ab$^{−1}$ . This is predicted to significantly improve the measurement of Higgs boson production at high transverse momentum. A luminosity measurement based on the multiplicity of charged particle tracks is presented. This is used to perform corrections to the stability and scale of the ATLAS lu-minosity measurement in data collected in 2012, 2015 and 2016. Along with other offline measurements it is used to constrain the calibration transfer and long-term stability which are two of the dominant luminosity uncertainties.