The asymmetry $A_{LL}^{\cos2\phi}$ in the polarized proton-proton Drell-Yan process within TMD factorization

Abstract

We study the $\cos2\phi$ azimuthal asymmetry in doubly longitudinally polarized proton-proton Drell-Yan collisions within the transverse momentum dependent factorization framework. The asymmetry arises from the convolution of the longitudinal transversity distribution $h_{1L}^{\perp}$ for both protons. Using the Bacchetta-Delcarro-Pisano-Radici-Signori parametrization for the nonperturbative Sudakov form factor and the Wandzura-Wilczek approximation for the collinear $h_{1L}^{\perp}$, we predict the double spin asymmetry $A_{LL}^{\cos2\phi}$ at RHIC and NICA kinematics. Our results demonstrate sensitivity to sea quark distributions, with the asymmetry reaching up to $25\%$ for maximal sea quark contributions. These predictions highlight the potential of polarized Drell-Yan measurements to probe sea quark dynamics and advance our understanding of nucleon structure.