Azimuthal anisotropies at high-p_T from transverse momentum dependent (TMD) parton distribution and fragmentation functions

Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201.

^* e-mail: ismail.soudi@wayne.edu
^** e-mail: majumder@wayne.edu

Published online: 26 June 2024

Abstract

Unpolarized protons can generate transversely polarized quarks or linearly polarized gluons through a distribution known as the Boer-Mulders’ function. The fragmentation of similarly polarized partons to unpolarized hadrons is called the Collins’ function. Both of these functions include correlations between the spin or polarization and the relative transverse momentum of the incoming parton or outgoing hadron, with respect to the parent particle. We explore the effect of including these and other TMDs on the production of high-pT (unpolarized) hadron production from (unpolarized) proton-proton scattering. The resulting initial state anisotropies, modulated with similar final state effects, may account for the observed azimuthal anisotropy of the produced high transverse momentum hadrons, without modification to the angle integrated spectra (R_AA). This may be an explanation for the existence of a v₂ in high-pT hadron spectra in p-A collisions without any observable nuclear modification of the spectra.