We present predictions for the double parton scattering (DPS) four-jet production cross sections in pA collisions at the LHC. Relying on the experimental capabilities to correlate centrality with impact parameter B of the proton-nucleus collision, we discuss a strategy to extract the double parton scattering contributions in pA collisions, which gives direct access to double parton distribution in the nucleon. We show that the production cross sections via DPS of four jets, out of which two may be light-or heavy-quark jets, are large enough to allow the method to be used already with data accumulated in 2016 pA run.PACS numbers:
I. INTRODUCTIONThe flux of incoming partons in hadron-induced reactions increases with the collision energy so that multiple parton interactions (MPI) take place, both in pp and pA collisions. The study of MPIs started in eighties in Tevatron era [1-3], both experimentally and theoretically. Recently a significant progress was achieved in the study of MPI, in particular of double parton scattering (DPS). From the theoretical point of view a new self consistent pQCD based formalism was developed both for pp [4][5][6][7][8][9][10][11][12][13] and pA DPS collisions [14] (see [15] for recent reviews). Recent observations of double open charm [16][17][18][19] and same sign W W (ssW W ) production [20] clearly show the existence of DPS interactions in pp collisions.The MPI interactions play a major role in the Underlying Event (UE) and thus are taken into account in all MC generators developed for the LHC [21,22]. On the other hand the study of DPS will lead to understanding of two parton correlations in the nucleon. In particular the DPS cross sections involve new non-perturbative two-body quantities, the so-called two particle Generalised Parton Distribution Functions ( 2 GPDs), which encode novel features of the non-perturbative nucleon structure. Such distributions have the potential to unveil two-parton correlations in the nucleon structure [23,24] and to give access to information complementary to the one obtained from nucleon one-body distributions.The study of MPI and in particular of the DPS reactions in pA collisions is important for our understanding of MPI in pp collisions and it constitutes a benchmark of the theoretical formalism available for these processes. On the other hand the MPI in pA collisions may play an important role in underlying event (UE) and high multiplicity events in pA collisions. Moreover it was argued in Ref. [14] that they are directly related to longitudinal parton correlations in the nucleon.The theory of MPI and in particular DPS in pA collisions was first developed in [25], where it was shown that there are two DPS contributions at work in such a case. First, there is the so-called DPS1 contribution, depicted in the left panel of Fig. (1), in which two partons from the incoming nucleon interact with two partons in the target nucleon in the nucleus, making such a process formally identical to DPS in the pp collisions. Next there is a new type of contributi...