Double parton distributions of the pion

Abstract

We present a calculation of valence double parton distributions of the pion in the framework of chiral quark models. The result obtained at the low-energy quark model scale is particularly simple, where in the chiral limit a factorized form follows, $D(x_1,x_2,\vec{q})=\delta (1-x_1-x_2)F(\vec{q})$ with $x_{1,2}$ standing for the longitudinal momentum fractions of the valence quark and antiquark, and $\vec{q}$ denotes the relative transverse momentum. For $\vec{q}=\vec{0}$ the result satisfies the Gaunt-Sterling sum rules. The QCD evolution to higher scales is carried out within the dDGLAP framework. We argue that the ratios of the valence Mellin moments $⟨x_1^n{x}_2^m⟩/⟨x_1^n⟩⟨x_2^m⟩$, which do not depend on the dDGLAP evolution, provide particularly convenient measures of the longitudinal correlations between the partons. Such ratios could be probed in future lattice QCD simulations.

Comments: 6 pages, talk presented by WB at Excited QCD 2020, Krynica Zdrój, Poland, 2-8 February 2020