A search for physics beyond the standard model (SM) in final states with
an electron or muon and missing transverse momentum is presented. The analysis uses
data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the
CMS detector at the LHC in 2016–2018 and corresponding to an integrated luminosity of
138 fb−1
. No significant deviation from the SM prediction is observed. Model-independent
limits are set on the production cross section of W’ bosons decaying into lepton-plusneutrino final states. Within the framework of the sequential standard model, with the
combined results from the electron and muon decay channels a W’ boson with mass less
than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the
determination of the oblique electroweak W parameter, are presented using LHC data
for the first time. These results together with those from the direct W’ resonance search
are used to extend existing constraints on composite Higgs scenarios. This is the first
experimental exclusion on compositeness parameters using results from LHC data other
than Higgs boson measurements