Correlations in double parton distributions: effects of evolution

Abstract

We numerically investigate the impact of scale evolution on double parton distributions, which are needed to compute multiple hard scattering processes. Assuming correlations between longitudinal and transverse variables or between the parton spins to be present at a low scale, we study how they are affected by evolution to higher scales, i.e. by repeated parton emission. We find that generically evolution tends to wash out correlations, but with a speed that may be slow or fast depending on kinematics and on the type of correlation. Nontrivial parton correlations may hence persist in double parton distributions at the high scales relevant for hard scattering processes.Comment: 35 pages, 24 figures; v2: small corrections and improvement

Correlations in double parton distributions: perturbative and non-perturbative effects

“…Perturbative evolution of the dPDFs is summarized and discussed in appendix A; however let us anticipate the results in this example, proposed in ref. [40]. As it is done also in ref.…”

“…(2.17) can be found in ref. [40]). The combinations u − and u + are taken as representatives of the quark sector.…”

“…As it is done also in ref. [40], only the homogeneus part of dPDFs evolution is implemented, for the moment being, in our scheme. According to some studies, the inhomogeneus part could play some role in this phenomenology [35,43]; its analysis is beyond the scope of the present paper.…”

“…The exponent n has to be fixed phenomenologically, as seen in section 2.3.1 in the case of the model of ref. [40] and will be discussed in the next sections for the LF-approach;…”

“…As in ref. [40], for the moment being, only the homogeneus part of the evolution of dPDFs is performed. As already said, the Q 2 evolution of the k ⊥ dependence has not been investigated yet and is still a missing item in this phenomenology.…”