Azimuthal spin asymmetries in pion-polarized proton induced Drell–Yan process at COMPASS using holographic light-front QCD

We compute all the leading-twist azimuthal spin asymmetries in the pion-proton induced Drell–Yan process. These spin asymmetries arise from convolutions of the leading-twist transverse-momentum-dependent parton distributions (TMDs) of both the incoming pion and the target proton. We employ the holographic light-front pion wave functions for the pion TMDs, while for the proton TMDs, we utilize a light-front quark-spectator model constructed by the soft-wall AdS/QCD. The gluon rescattering is crucial to predict nonzero time-reversal odd TMDs. We study the utility of a nonperturbative SU(3) gluon rescattering kernel, which extends beyond the typical assumption of perturbative U(1) gluons. Subsequently, we employ Collins–Soper scale evolution at Next-to-Leading Logarithmic precision for the TMDs evolution. Our predictions for the spin asymmetries are consistent with the available experimental data from COMPASS and other phenomenological studies. We also present the cross section for the pion-nucleus induced Drell–Yan process with the obtained pion TMDs supplemented by the TMDs of the target nucleus.