Search for dark matter particles in W<SUP>+</SUP>W<SUP>-</SUP> events with transverse momentum imbalance in proton-proton collisions at √<i>s</i>=13 TeV

A search for dark matter particles is performed using events with a pair of W bosons and large missing transverse momentum. Candidate events are selected by requiring one or two leptons (l = electrons or muons). The analysis is based on proton-proton collision data collected at a center-of-mass energy of 13TeV by the CMS experiment at the LHC and corresponding to an integrated luminosity of 138 fb(-1). No significant excess over the expected standard model background is observed in the l nu qq and 2l2 nu final states of the W+W- boson pair. Limits are set on dark matter production in the context of a simplified dark Higgs model, with a dark Higgs boson mass above the W+W- mass threshold. The dark matter phase space is probed in the mass range 100-300 GeV, extending the scope of previous searches. Current exclusion limits are improved in the range of dark Higgs masses from 160 to 250 GeV, for a dark matter mass of 200 GeV.