Measurement of inclusive and differential cross sections for single top quark production in association with a W boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Measurements of the inclusive and normalised differential cross sections are
presented for the production of single top quarks in association with a W boson in protonproton collisions at a centre-of-mass energy of 13 TeV. The data used were recorded with the
CMS detector at the LHC during 2016–2018, and correspond to an integrated luminosity of
138 fb
−
1
. Events containing one electron and one muon in the final state are analysed. For
the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties
of the events is used to separate the signal from the dominant
t
¯t background. A cross section
of 79
.
2
±
0
.9 (stat) +7
.
7
−
8
.
0 (syst)
±
1
.2 (lumi) pb is obtained, consistent with the predictions
of the standard model. For the differential measurements, a fiducial region is defined
according to the detector acceptance, and the requirement of exactly one jet coming from
the fragmentation of a bottom quark. The resulting distributions are unfolded to particle
level and agree with the predictions at next-to-leading order in perturbative quantum
chromodynamics.