Two-gluon production of $\phi$ and $\eta'$ mesons in proton-proton collisions at high energies

TL;DR

This paper investigates gluon-gluon fusion mechanisms for producing $ta'$ and $$ mesons in high-energy proton-proton collisions, calculating cross sections and transverse momentum distributions, and comparing with experimental data and models.

Contribution

It introduces a detailed calculation of meson production via gluon-gluon fusion using the $k_t$-factorization approach, including form factors from light-cone wave functions, and compares results with experimental data and other models.

Findings

Gluon-gluon fusion is not the dominant production mechanism for $ta'$ and $$ mesons.

Higher-twist effects may persist at large photon virtualities.

The model's predictions align variably with experimental data, especially at higher energies.

Abstract

We discuss gluon-gluon mechanisms for production of mesons with hidden strangeness, such as $\eta'$ and $\phi$ meson, in proton-proton collisions at large energies. The $g^* g^* \to \eta'$ and $g^* g^* \to \phi g$ mechanisms are considered only and the corresponding cross sections are calculated in the $k_t$-factorization approach. The $F_{\gamma^* \gamma^* \to \eta'}$ and $F_{g^* g^* \to \eta'}$ form factors are calculated from quark-antiquark $\eta'$ light-cone wave function including quark/antiquark transverse momenta. The result for two-photon transition form factor demonstrates that higher twists may survive even to large photon virtualities. The result is compared with the result of a recent leading-twist NLO analysis which uses phenomenological distribution amplitudes fitted to exclusive production of $\eta'$ in $e^+ e^- \to e^+ e^- \eta'$ reaction. We calculate transverse momentum distributions of both $\eta'$ and $\phi$ mesons in proton-proton collisions for RHIC and LHC energies. The results are compared to experimental data whenever available. The results of the Lund string model are shown for comparison for $\eta'$ production at LHC energies. It seems that the two-gluon fusion is not the dominant mechanism for both $\phi$ and $\eta'$ production, although the situation for $\eta'$, especially at larger energies, is less clear due to lack of experimental data.