Double parton scattering contribution toW+jets

Elements of a theory for multiparton interactions in QCD

“…If the two partons initiating the two hard scatters in the amplitude come from the splitting of a single parton, we have graphs like in figure 38. 17 For graph 38a one finds the same scaling behavior (5.32) as for graph 37a, and for graph 38b one finds the same scaling behavior (5.33) as for graph 37b.…”

“…Using that the transverse-momentum dependent density depends only on the square of k we then have 17) and comparing with the DGLAP equation for the l.h.s. we can identify the kernel in (5.15) as the familiar splitting function.…”

“…The effects of such multiparton interactions are suppressed or average out in sufficiently inclusive observables, but they have important consequences for the details of the hadronic final state. The possible importance of multiparton interactions has been realized long ago [1,2] and phenomenological estimates have been given for many final states such as four jets (possibly including b quarks) [3][4][5][6][7][8][9], jets associated with photons or leptons [10], four leptons produced by the double Drell-Yan process [11][12][13] or from two charmonium states [14][15][16], as well as a number of channels with electroweak gauge bosons [17][18][19][20][21][22][23][24][25][26]. Experimental evidence for multiple hard scattering has been found in the production of multijets [27][28][29] and of a photon associated with three jets [30][31][32][33].…”

Angular correlations in the double Drell-Yan process

“…We split the cross section (2.14) into three parts, σ (0) for the case without transverse quark polarization and σ (1) , σ (2) for the cases where one or two hard interactions are initiated by transversely polarized quarks. The contribution with only unpolarized and longitudinally polarized partons reads …”

“…Among these aspects are multiparton interactions, where in a single proton-proton collision more than one parton in each proton participates in a hard scattering. Multiparton interactions can give sizeable contributions both to signal and to background processes, notably to Higgs production [1], to electroweak processes [2][3][4][5][6][7][8][9][10] and to multijet production [11][12][13][14][15][16][17][18]. They are also of interest in their own right from the point of view of hadron structure, because they contain information about correlations between partons inside the proton.…”