The $2\pi$ Subsystem in Diffractively Produced $\pi^-\pi^+\pi^-$ at COMPASS
Abstract
The COMPASS experiment at CERN has collected a large dataset of million events produced diffractively from a proton target using a pion beam. The partial-wave analysis (PWA) of these high-precision data reveals previously unseen details but is limited in parts by systematic effects. The PWA is based on the isobar model, in which multi-particle decays are described as a chain of subsequent two-body decays. Here, fixed mass distributions for the appearing intermediate resonances, the so-called isobars, are assumed. These shapes, which e.g. may be parametrized by Breit-Wigner amplitudes, represent prior knowledge that has to be put into the analysis model and may therefore introduce a model dependence, thus increasing systematic uncertainties. We present a novel method, which allows to extract isobar amplitudes directly from the data in a more model-independent way. As a first application, diffractively produced events are analyzed. Here, the focus lies in particular on the scalar subsystem, where in a previous analysis a signal for a new axial-vector state was found in the decay mode.
Keywords
Cite
@article{arxiv.1512.04249,
title = {The $2\pi$ Subsystem in Diffractively Produced $\pi^-\pi^+\pi^-$ at COMPASS},
author = {Fabian Krinner},
journal= {arXiv preprint arXiv:1512.04249},
year = {2017}
}