Abstract
One of the main challenges hampering an accurate measurement of the double parton scattering (DPS) cross sections is the difficulty in separating the DPS from the leading twist (LT) contributions. We argue that such a separation can be achieved, and cross section of DPS measured, in proton–nucleus scattering by exploiting the different centrality dependence of DPS and LT processes. We developed a Monte Carlo implementation of the DPS processes which includes realistic nucleon–nucleon (NN) correlations in nuclei, an accurate description of transverse geometry of both hard and soft NN collisions as well as fluctuations of the strength of interaction of nucleon with nucleus (color fluctuation effects). Our method allows the calculation of probability distributions of single and double dijet events as a function of centrality, also distinguishing double hard scatterings originating from a single target nucleon and from two different nucleons. We present numerical results for the rate of DPS as a function of centrality, following the model developed by the ATLAS collaboration which relates the distribution over the number of wounded nucleons to the distribution over the sum of transverse energies of hadrons produced at large negative (along the nucleus direction) rapidities, which is experimentally measurable. We suggest a new quantity which allows to test the geometry of DPS and we argue that it is a universal function of centrality for different DPS processes. This quantity can be tested by analyzing existing LHC data. The method developed in this work can be extended to the search for triple parton interactions.
Highlights
A number of experimental analyses have been performed, aiming at finding an optimal kinematics where the ratio of the cross sections of double parton scattering (DPS) to the competing leading twist processes are somewhat enhanced
One of the main challenges hampering an accurate measurement of the double parton scattering (DPS) cross sections is the difficulty in separating the DPS from the leading twist (LT) contributions
We argue that such a separation can be achieved, and cross section of DPS measured, in proton–nucleus scattering by exploiting the different centrality dependence of DPS and LT processes
Summary
A number of experimental analyses have been performed, aiming at finding an optimal kinematics where the ratio of the cross sections of DPS to the competing leading twist processes are somewhat enhanced. [17], which takes into account both the mean field contributions as well pQCD-induced parton–parton correlations and small x soft correlations This formalism allows to describe all existing LHC data except double J/ψ production [18]. We study the centrality dependence of the different contributions to DPS in p A collisions at LHC energies, within a high-accuracy implementation of the Glauber Monte Carlo model. In the treatment of the individual soft pN collisions, we include the color fluctuation effect [24], which takes into account the possibility for the incoming proton to fluctuate in different quantum states with substantially different pN interaction strength; this effect is important for an accurate description of the dependence of the hadron production on centrality [25]; see discussion in Sect. Page 3 of 9 482 culation we outline the proposed procedure for comparing events of different centrality classes in order to measure the DPS cross section
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