Numerical Study of MRW-Type Unintegrated Double Parton Distribution Functions from Non-Factorized DPDFs

Abstract

Double parton scattering provides a sensitive probe of multiparton correlations inside hadrons. In this work we present a numerical study of unintegrated double parton distribution functions constructed from non-factorized collinear DPDFs. As input we use the \texttt{GS09} DPDFs and evolve them to unequal scales with a numerical double DGLAP evolution framework, which is validated through the corresponding momentum and valence-number sum rules. We investigate MRW-inspired prescriptions for generating transverse momentum dependence in the double parton case. In particular, we study the double LO-MRW approach (DLO-MRW) in the perturbative region, the double modified KMRW approach (DMKMRW), the double virtuality ordered MRW (DVO-MRW) model, and a normalization-matched version of the latter. The DMKMRW, DVO-MRW, and matched DVO-MRW prescriptions can be applied directly to the full collinear DPDF, including its nonhomogeneous component, and avoid the piecewise treatment required in the conventional LO-MRW construction. We analyze the normalization, transverse momentum dependence, flavor dependence, and sensitivity to longitudinal DPDF correlations of the resulting distributions. The DMKMRW model is normalization preserving by construction, while the DVO-MRW model shows nontrivial normalization deviations that are removed in the matched version. Non-factorized effects are strongly channel-dependent. In DMKMRW, they enter mainly through longitudinal DPDF correlations, whereas in the LO-MRW and virtuality-ordered models, they also modify the transverse momentum shape. The largest deviations occur near the double parton kinematic boundary and in channels affected by valence-number and quark-antiquark correlations.