Exclusive scalar $f_0(1500)$ meson production for energy ranges available at the GSI Facility for Antiproton and Ion Research (GSI-FAIR) and at the Japan Proton Accelerator Research Complex (J-PARC)

TL;DR

This paper evaluates the production mechanisms and differential distributions of the scalar meson $f_0(1500)$ at energies relevant to GSI-FAIR and J-PARC, including both QCD diffractive and pion-pion exchange processes, providing new theoretical insights and predictions.

Contribution

It introduces the first calculation of both QCD diffractive and meson exchange mechanisms for $f_0(1500)$ production at these energies, including the use of various unintegrated gluon distribution functions.

Findings

Pion-pion fusion dominates near threshold energies.

Gluonic diffractive mechanisms are negligible at PANDA energies.

Predicted large cross sections for pion-pion fusion at PANDA energies.

Abstract

We evaluate differential distributions for exclusive scalar $f_0(1500)$ meson (glueball candidate) production for $p \bar p \to N_1 N_2 f_0$ (FAIR@GSI) and $p p \to p p f_0$ (J-PARC@Tokai). Both QCD diffractive, pion-pion meson exchange current (MEC) components as well as double-diffractive mechanism with intermediate pionic loop are calculated for the first time in the literature. The pion-pion component, which can be reliably calculated, dominates close to the threshold while the diffractive component may take over only for larger energies. At the moment only upper limit for the QCD-diffractive component can be obtained. The diffractive component is calculated based on two-gluon impact factors as well as in the framework of Khoze-Martin-Ryskin approach proposed for diffractive Higgs boson production. Different unintegrated gluon distribution functions (UGDFs) from the literature are used. Rather large cross sections due to pion-pion fusion are predicted for PANDA energies, where the gluonic mechanism is shown to be negligible. The production of $f_0(1500)$ close to threshold could limit the so-called $\pi NN$ form factor in the region of larger pion virtualities. We discuss in detail the two-pion background to the production of the $f_0(1500)$ meson. We compare our result with the existing data of %the WA102 Collaboration.