Heidelberg 2015 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 9: Hadron Structure and Spectroscopy 2
HK 9.5: Talk
Monday, March 23, 2015, 16:00–16:15, T/SR25
Observation of a new narrow axial-vector meson a1(1420) in diffractively produced π−π+π− final states at COMPASS — •Stefan Wallner1 and Compass Collaboration2 — 1TU München E18 — 2Cern
The COMPASS experiment studies the spectrum of hadrons and has acquired a large data sample of diffractively produced π−π+π− final states using a 190 GeV pion beam on a hydrogen target. The size of the data set permits to perform a partial-wave analysis with the largest wave set used so far consisting of 88 waves in bins of the squared four-momentum transfer t′ from the beam to the target.
Based on this partial-wave decomposition, resonance parameters can be extracted by disentangling resonant and non-resonant parts of the partial waves in mass-dependent fits. The additional information obtained from the division in bins of the squared four-momentum transfer t′, allows for a better separation of resonant and non-resonant parts, as they exhibit different t′-dependences.
Using this method, the resonance parameters of a new axial-vector state, the a1(1420), observed only in the f0(980) π decay mode, have been extracted.
We will present extensive studies that have been performed in order to investigate the systematic uncertainties of the resonance parameters, due to the applied fit model, the correlation with other waves or the event selection.
Supported by BMBF, MLL and the Excellence Cluster Universe.