Evidence for WW production from double-parton interactions in proton-proton collisions at root s=13 TeV

A search for (\text{WW}) production from double-parton scattering processes using same-charge electron-muon and dimuon events is reported, based on proton-proton collision data collected at a center-of-mass energy of (13\phantom{\rule{0.166667em}{0ex}}\text{TeV}). The analyzed data set corresponds to an integrated luminosity of (77.4\phantom{\rule{0.166667em}{0ex}}{\text{fb}}^{-1}), collected using the CMS detector at the LHC in 2016 and 2017. Multivariate classifiers are used to discriminate between the signal and the dominant background processes. A maximum likelihood fit is performed to extract the signal cross section. This leads to the first evidence for (\text{WW}) production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is (1.41±0.28\phantom{\rule{0.166667em}{0ex}}\text{(stat)}±0.28\phantom{\rule{0.166667em}{0ex}}\text{(syst)}\phantom{\rule{0.166667em}{0ex}}\text{pb}).