Speaker
Prof.
D0 H1
(DESY, FNAL)
Description
Photoproduction data of HERA are analyzed by requiring dijets with transverse momenta of at least 5 GeV. The two jets define in azimuth a towards region (leading jet) and an away region (2nd jet) and transverse regions between them. The charged particle multiplicity is measured in these regions as a function of the variables x_{gamma} and pT_{leading jet}. Models which include contributions of multiparton interactions are able to describe the measurement, whereas predictions without them lie below the measurements, especially at low x_{gamma}, the region of enhanced contributions from the resolved photon.
Double parton (DP) interactions in “gamma + 3 jet” events in p-pbar collisions at
sqrt{s}=1.96TeV are studied basing on the sample of “gamma + 3jet” events collected in the D0 experiment with an integrated luminosity of 1fb^{-1}. The fraction f{DP} of the events with double parton scattering is determined. The events are selected with photon candidate transverse momentum 60 < pT^{gamma} < 80 GeV. The leading jet pT ^{jet} > 25 GeV and two additional jets with pT > 15 GeV. The values of f{DP} are measured in three intervals of the transverse momentum pT^{jet2} of the second jet which spans the range of 15 - 30 GeV. It is found that the f{DP}fractions drop with increasing of pT^{jet2}. The effective cross section sigma_{eff} (a process-independent parameter which contains an information about the parton density inside the proton and about the parton correlations) is calculated in the same three pT^{jet2} intervals. The average value over these three pT^{jet2} intervals is sigma_{eff}^{aver} = 15.1 +/- 1.9 mb.
Primary author
Prof.
D0 H1
(DESY, FNAL)
