Measurement of the fiducial and differential cross-section of $WH/ZH$ production for the $b$-jets + $E_\text{T}^\text{miss}$ final state in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

Fiducial and differential cross-sections of Higgs boson production in association with a $W$ or $Z$ boson are measured in final states with missing transverse momentum where the Higgs boson decays into a $b\bar{b}$ pair. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 $\textrm{fb}^{-1}$. The fiducial cross-sections are reported in two bins of missing transverse momentum, $150 \text{ GeV} \leq E_\text{T}^\text{miss} < 250\text{ GeV}$ and $E_\text{T}^\text{miss} \geq {250}\text{ GeV}$. The measured cross-section values of $5.5 \pm 2.6\,(\text{stat.}) \pm 3.2\,(\text{syst.})\,\text{ fb}$ and $1.9 \pm 0.7\,(\textrm{stat.}) \pm 0.4\,(\text{syst.})\,\text{ fb}$ are in good agreement with the Standard Model predictions of $5.8 \pm {0.3}\text{ fb}$ and $1.5 \pm {0.1}\text{ fb}$