First measurement of the helicity dependence for the gamma p -> p pi(+)pi(-) reaction

ISSN
1434-6001
Date Issued
2007
Author(s)
Ahrens, J.
Altieri, S.
Annand, J. R. M.
Arends, H.-J.
Beck, R.
Blackston, M. A.
Bradtke, C.
Braghieri, A.
d'Hose, N.
Dutz, H.
Fix, A.
Goertz, S.
Grabmayr, P.
Hasegawa, S.
Heid, E.
Holvoet, H.
Horikawa, N.
Iwata, T.
Jennewein, P.
Klein, F.
Kondratiev, R.
Lang, M.
Lannoy, B.
Lisin, V.
Martinez-Fabregate, M.
McGeorge, J. C.
Meyer, Werner
Panzeri, A.
Pedroni, P.
Pinelli, T.
Preobrajenski, I.
Reicherz, G.
Rohlof, Ch.
Rosner, G.
Rost, M.
Rostomyan, T.
Ryckbosch, D.
Schumacher, M.
Seitz, Bjoern
Tamas, Gabor
Thomas, Andy
de Vyver, R. van
Weller, H. R.
Zapadtka, F.
DOI
10.1140/epja/i2007-10491-5
Abstract
The helicity dependence of the total cross-section and the invariant-mass distributions in the (p pi(+/-)) and (pi(+) pi(-)) final states for the gamma p -> p pi(+)pi(-) reaction have been measured for the first time at incident photon energies from 400 to 800MeV. The measurement was performed with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. Although this channel is found to be predominantly excited by the intermediate production of a Delta pi state, both the measured unpolarized and the helicity-dependent observables are generally not well described by the existing theoretical models.