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HK: Fachverband Physik der Hadronen und Kerne

HK 29: Hadron Structure and Spectroscopy III

HK 29.1: Group Report

Wednesday, March 12, 2025, 15:45–16:15, HS 3 Physik

Light-Meson Spectroscopy at COMPASS — •Julien Beckers for the COMPASS collaboration — Technische Universität München

COMPASS is a multi-purpose fixed-target experiment at the CERN SPS. One of its main goals is to probe the strong interaction at low energies by studying the excitation spectrum of light mesons in diffractive scattering reactions of a 190 GeV/c hadron beam. This is done by decomposing the data into partial-wave amplitudes with well-defined quantum numbers and searching for resonances in these amplitudes.

We have collected the world’s largest datasets of various final states. First and foremost, COMPASS’ flagship πππ+ channel has allowed high-precision measurements of many light mesons. Its strange equivalent, Kππ+, has given insight into the lesser known strange-meson spectrum. New analyses of final states with kaons complement their findings. After briefly presenting the analysis method, we will discuss measurements in the KS0 K final state, which gives access exclusively to aJ mesons at higher invariant masses.

COMPASS has also contributed significantly in the search for exotic (non-qq) mesons. We will present novel analyses of the ωππ0 and πππ+η final states, which are especially interesting as the lightest hybrid meson is theorized to decay into both of these final states.

The COMPASS data also allows for measurements beyond typical spectroscopy. We will discuss one such analysis of the nonresonant double-Regge exchange process, done in collaboration with JPAC.

Funded by the DFG under Germany’s Excellence Strategy - EXC2094 - 390783311.

Keywords: COMPASS; meson spectroscopy; partial-wave analysis; exotic mesons

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