Measurement of double-parton interactions in W+2 jets events with the CMS detector

Double parton scattering is investigated in proton-proton collisions at $\sqrt{s} = 7$ TeV where the final state includes a W boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 fb$^{-1}$, collected with the CMS detector at the LHC. Observables sensitive to double parton scattering are investigated after being corrected for detector effects and selection efficiencies. The fraction of W+ 2-jet events due to double parton scattering is measured to be 0.055 $\pm$ 0.002 (stat.) $\pm$ 0.014 (syst.). The effective cross section, $\sigma_{\text{eff}}$, characterizing the effective transverse area of hard partonic interactions in collisions between protons is measured to be 20.7 $\pm$ 0.8 (stat.) $\pm$ 6.6 (syst.) mb.