Central exclusive production of $\eta$ and $\eta'$ mesons in diffractive proton-proton collisions at the LHC within the tensor-pomeron approach

TL;DR

This paper models the central exclusive production of $ta$ and $ta'$ mesons in high-energy proton-proton collisions at the LHC using the tensor-pomeron approach, fitting parameters to existing data and predicting cross sections and distributions.

Contribution

It introduces a tensor-pomeron model for CEP of pseudoscalar mesons, fitting parameters to WA102 data and providing predictions for LHC energies, including cross sections and differential distributions.

Findings

Predicted cross sections for $ta$ and $ta'$ production at LHC energies.

Upper limits for $ta$ production cross section in specific pseudorapidity ranges.

Evidence that scalar-pomeron models cannot produce $ta$, $ta'$, or $f_1(1285)$ in CEP, supporting tensor-pomeron approach.

Abstract

We present a study of the central exclusive production (CEP) of $\eta$ and $\eta'(958)$ mesons in diffractive proton-proton collisions at high energies. The amplitudes, including pomeron and $f_{2 \mathbb{R}}$ reggeon exchanges, are calculated within the tensor-pomeron model. Absorption effects are also taken into account at the amplitude level. We fit some undetermined model parameters (coupling constants and cutoff parameters in form factors) to the WA102 experimental data and then make predictions for the LHC energy $\sqrt{s} = 13$ TeV. Both, total cross sections and several differential distributions are presented. For $pp \to pp \eta$, we find an upper limit for the total cross section of 2.5 $\mu$b for pseudorapidity of the $\eta$ meson $|\eta_{M}| < 1$ and 5.6 $\mu$b for $2 < \eta_{M} < 5$. For $pp \to pp \eta'$, we predict the cross section to be in the range of 0.3-0.7 $\mu$b for pseudorapidity of the $\eta'$ meson $|\eta_{M}| < 1$ and 0.9-2.1 $\mu$b for $2 < \eta_{M} < 5$. This opens the possibility to study diffractive production of pseudoscalar mesons in experiments at the LHC. We discuss if there are arguments from SU(3)-flavor symmetry which would forbid pomeron-pomeron fusion giving an $\eta$ meson. In our opinion such arguments do not exist. We also consider CEP of the pseudoscalars $\eta$ and $\eta'(958)$ and the pseudovector meson $f_{1}(1285)$ in diffractive proton-proton collisions in a theory with a scalar pomeron. We show that none of these particles can be produced in this way in the scalar-pomeron theory. Thus, experimental observation of any of these particles in the above CEP processes at the LHC would give striking evidence against a scalar character of the pomeron.