Bochum 2018 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 38: Hadron Structure and Spectroscopy VII

HK 38.4: Talk

Wednesday, February 28, 2018, 17:30–17:45, HZO 80

Freed-isobar Partial-Wave Analysis of the Spin-Exotic J^PC = 1⁻⁺ Wave at COMPASS — •Dmitri Rybachikov for the COMPASS collaboration — Physik-Department E18, Technische Universität München

COMPASS is a multi-purpose fixed-target experiment at the CERN Super Proton Synchrotron aimed at studying the structure and spectrum of hadrons. The spectrum of isovector light-meson resonances is studied in diffractive-dissociation reactions using a 190 GeV/c π⁻ beam. The flagship channel is the π⁻π⁻π⁺ final state, for which COMPASS has recorded a large data sample of 46 million events. From these data, 3π resonances are extracted by performing a partial-wave analysis (PWA) using the isobar model. The model depedence of the PWA result is studied using a novel method, the freed-isobar PWA, which extracts the amplitudes of the π⁻π⁺ subsytems from the data. Using this method, we studied the spin-exotic partial wave with J^PC = 1⁻⁺ quantum numbers, which decays via an isovector π⁻π⁺ subsystem with J^PC = 1^–. This wave is of particular interest because it has quantum numbers that are forbidden for qq systems in the non-relativistic limit. Continuous mathematical ambiguites may arise in the freed-isobar approach. We will discuss methods to resolve these ambiguities and present results of this analysis.

This work was supported by the BMBF, the DFG Cluster of Excellence “Origin and Structure of the Universe” (Exc 153), and the Maier-Leibnitz-Laboratorium der Universität und der Technischen Universität München.