Light Scalar Mesons in Central Production at COMPASS

TL;DR

This paper reports on the analysis of light scalar mesons produced centrally in proton-proton collisions at CERN, aiming to identify glueballs and understand meson decay dynamics through partial wave analysis.

Contribution

It presents a detailed partial wave analysis of neutral resonances in central production, addressing mathematical ambiguities and exploring resonance parameterizations with a large dataset.

Findings

Identification of scalar meson resonances

Analysis of decay angular distributions

Insights into meson-glueball mixing

Abstract

COMPASS is a fixed-target experiment at the CERN SPS that studies the spectrum of light-quark hadrons. In 2009, it collected a large dataset using a $190\,$GeV$/c$ positive hadron beam impinging on a liquid-hydrogen target in order to measure the central exclusive production of light scalar mesons. One of the goals is the search for so-called glueballs, which are hypothetical meson-like objects without valence-quark content. We study the decay of neutral resonances by selecting centrally produced pion pairs from the COMPASS dataset. The angular distributions of the two pseudoscalar mesons are decomposed in terms of partial waves, where particular attention is paid to the inherent mathematical ambiguities. The large dataset allows us to perform a detailed analysis in bins of the two squared four-momentum transfers carried by the exchange particles in the reaction. Possible parameterisations of the mass dependence of the partial-wave amplitudes in terms of resonances are also discussed.