Testing the scale dependence of the scale factor σ eff in double dijet production at the LHC

Elements of a theory for multiparton interactions in QCD

“…In different forms, this relation (or more precisely its analog for quarks and gluons instead of scalar partons) has long been used as a starting point of phenomenological studies, see e.g. [68][69][70][71][72] and [8,73]. 2 As observed in [60] for the case of collinear distributions, the reduction of multiparton to single-parton distributions also takes a simple form in the transverse-momentum representation.…”

“…It seems plausible to assume that this is a reasonable first approximation, at least in a certain region of variables, but one should not expect it to be very precise. Possible deviations from this approximation and their phenomenological consequences have recently been discussed in [8,[74][75][76][77][78].…”

“…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

“…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.…”

“…This leads to very compact results, but it certainly is a simplification whose validity and limitations need to be investigated. Recent phenomenological studies of different types of correlation effects in multiparton interactions can be found in [17,34,[48][49][50][51][52]. In this work we focus on correlations between the polarization of two partons in an unpolarized proton and on their consequences for the overall rate and for final-state distributions in double hard scattering processes.…”