Production of $f_2(1270)$ meson in $pp$ collisions at the LHC via gluon-gluon fusion in the $k_t$-factorization approach

TL;DR

This paper calculates the production cross section of the $f_2(1270)$ meson in proton-proton collisions at the LHC using the $k_t$-factorization approach, comparing results with experimental data and discussing saturation effects.

Contribution

It introduces a detailed calculation of $f_2(1270)$ production via gluon-gluon fusion with various unintegrated gluon distributions, exploring different tensorial parametrizations and their impact.

Findings

Results depend strongly on the form factor parametrization.

Agreement with ALICE data achieved at higher transverse momenta.

No clear evidence of saturation effects observed.

Abstract

We calculate inclusive cross section for $f_2(1270)$ tensor meson production via color singlet gluon-gluon fusion in the $k_t$-factorization approach with unintegrated gluon distribution functions (UGDFs). The process may be potentially interesting in the context of searches for saturation effects. The energy-momentum tensor, equivalent to helicity-2 coupling, and helicity-0 coupling are used for the $g^* g^* \to f_2(1270)$ vertex. Two somewhat different parametrizations of helicity-2 and helicity-0 tensorial structure from the literature are used in our calculations. Some parameters are extracted from $\gamma \gamma \to f_2(1270) \to \pi \pi$ reactions. Different modern UGDFs from the literature are used. The results strongly depend on the parametrization of the $g^* g^* \to f_2(1270)$ form factor. Our results for transverse momentum distributions of $f_2$ are compared to preliminary ALICE data. We can obtain agreement with the data only at larger $f_2(1270)$ transverse momenta only for some parametrizations of the $g^* g^* \to f_2(1270)$ form factor. No obvious sign of the onset of saturation is possible. At low transverse momenta one needs to include also the $\pi\pi$ final-state rescattering. The agreement with the ALICE data can be obtained by adjusting probability of formation and survival of $f_2(1270)$ in a harsh quark-gluon and multipion environment. The pomeron-pomeron fusion mechanism is discussed in addition and results are quantified.