Speaker
Description
The TMD factorization is a consistent framework to describe hadron processes at small transverse momenta [1], though there are several approaches for modeling TMD parton distributions. The Soft Gluon Resummation approach is such a model that allows to express TMD parton distributions via collinear ones and nonperturbative phenomenological part [2]. Evolution of perturbative part is controlled with Collins-Soper equations and can be derived as Sudakov factor [3]. Parton distributions for initial unpolarized protons can be written in terms of TMD unpolarized parton distributions and Boer-Mulders functions that refer to linearly polarized partons in unpolarized nucleons [4]. Charmonium production in proton-proton collisions is an appropriate process to estimate these contributions. Contribution of unpolarized parton distributions have already been investigated in Refs. [5, 6] and now we focus on linearly polarized gluons and report on $J/\psi$ and $\eta_c^{}$ production at $p_T^{} \ll M$ with $M$ as a mass of charmonium, for $\sqrt{s} \leqslant 200$ GeV, including 27 GeV for the forthcoming experiments of SPD NICA. Hadronization of produced quarks into charmonium is considered within the NRQCD framework [7].
References:
[1] J. C. Collins, Foundations of Perturbative QCD (2011).
[2] J. Bor, D. Boer, Phys. Rev. D 106 (2022) 1, 014030.
[3] J. C. Collins, D. E. Soper, Nucl. Phys. B 193 (1981) 381.
[4] P. J. Mulders, J. Rodrigues, Phys. Rev. D 63 (2001) 094021.
[5] V. A. Saleev, K. K. Shilyaev, Phys. Atom. Nucl. 88 (2025) 2, 338-341.
[6] V. A. Saleev, K. K. Shilyaev, arXiv:2502.16461 [hep-ph] (2025).
[7] G. T. Bodwin, E. Braaten, G. P. Lepage, Phys. Rev. D 51 (1995) 1125-1171.
