Study of Double Parton Scattering Using Four-Jet Scenarios

Abstract

Measurements of the dierential cross sections for multijet scenarios in proton-proton collisions are presented as a function of the transverse momentum p T and pseudorapi- dity , together with the correlations in azimuthal angle and the p T balance among the jets. Two dierent scenarios are separately studied; in the rst one an exclusive four-jet nal state is selected in j j 50 GeV each, together with two jets of p T > 20 GeV each. No other jets with p T > 20 GeV are allowed in the selected events. In the second one at least four jets with p T > 20 GeV are required: two of the four selected jets are asked to be originated by a b-quark in j j < 2.4, while no requests on the avour of the other two jets, which are selected within j j < 4.7 are applied. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of 36 pb-1. The total cross section is measured to be (pp ! 4j+X) = 330 5 (stat.) 45 (syst.) and (pp ! 2b+2j+X) = 67 : 2 2 : 2 (stat.) 22 : 5 (syst.) for, respectively, the two selected multijet scenarios. It is found that xed-order matrix element calculations including parton showers describe the measured dierential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data. A new method of extraction of double parton scattering contributions from an experimental measurement is introduced for the rst time: it is applied to W+dijet measurements and to both multijet channels. Values of eff are measured to be 19.0 +4 : 6 mb and 23.2 +3 : 3 mb for the two examined selections. These values are consistent between each other and compatible with measurements based on dierent physics channels at 7 TeV.