Speaker
Stefanie Grabmüller
(TU München)
Description
COMPASS is a multi-purpose fixed-target experiment at CERN SPS, that investigates the structure and spectroscopy of hadrons. Dissociation of pions on nuclear or hydrogen targets provides clean access to the light meson spectrum. During a short run with 190 GeV/c pi- beam on lead in the year 2004, about 4 million exclusive pi-pi-pi+ events have been collected. For the 3 million events with low momentum transfer t'<0.01 (GeV/c)^2, coherent scattering off the nucleus as a whole can be assumed, with contributions from Reggeon (Pomeron) and photon exchange. For the lowest t'<0.001 (GeV/c)^2, the electromagnetic interaction part becomes apparent.
The status of the partial-wave analysis of these data will be presented, focussing on new techniques for the extraction of the contribution from photon exchange at low masses. Its measured absolute cross-section is compared to ChPT calculations.
Primary author
Stefanie Grabmüller
(TU München)
