Measurement of cross sections for production of a $𝑍$ boson in association with a flavor-inclusive or doubly $𝑏$-tagged large-radius jet in proton-proton collisions at √s=13  $TeV$ with the ATLAS experiment

We present measurements of cross sections for production of a leptonically decaying 𝑍 boson in association with a large-radius jet in 13 TeV proton-proton collisions at the LHC, using 36 fb−1 of data from the ATLAS detector. Integrated and differential cross sections are measured at particle level in both a flavor inclusive and a doubly 𝑏-tagged fiducial phase space. The large-radius jet mass and transverse momentum, its kinematic relationship to the 𝑍 boson, and the angular separation of 𝑏-tagged small-radius track jets within the large-radius jet are measured. This measurement constitutes an important test of perturbative quantum chromodynamics in kinematic and flavor configurations relevant to several Higgs boson and beyond-Standard-Model physics analyses. The results highlight issues with modeling of additional hadronic activity in the flavor-inclusive selection, and a distinction between flavor-number schemes in the 𝑏-tagged phase space.