{
  "id": "1512.04249",
  "version": "v1",
  "published": "2015-12-14T10:41:55.000Z",
  "updated": "2015-12-14T10:41:55.000Z",
  "title": "The $2π$ Subsystem in Diffractively Produced $π^-π^+π^-$ at COMPASS",
  "authors": [
    "Fabian Krinner"
  ],
  "journal": "Proceedings for the HADRON 2015 conference from 13 September 2015 to 18 September 2015, 6 pages, 18 figures",
  "categories": [
    "hep-ex",
    "hep-ph"
  ],
  "abstract": "The COMPASS experiment at CERN has collected a large dataset of $50$ million $\\pi^-\\pi^+\\pi^-$ events produced diffractively from a proton target using a $190\\,\\mathrm{GeV}/c$ 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 $\\pi^-\\pi^+\\pi^-$ events are analyzed. Here, the focus lies in particular on the scalar $\\pi^+\\pi^-$ subsystem, where in a previous analysis a signal for a new axial-vector state $a_1(1420)$ was found in the $f_0(980)\\pi$ decay mode.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-12-14T10:41:55.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "extract isobar amplitudes",
      "represent prior knowledge",
      "subsequent two-body decays",
      "first application",
      "proton target"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1063/1.4949396"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015arXiv151204249K",
      "inspire": 1409493
    }
  }
}