Intermediate resonance excitation in the gamma p -> p pi(0)pi(0) reaction

ISSN
1873-2445
0370-2693
Date Issued
2005
Author(s)
Ahrens, J.
Altieri, S.
Annand, JRM
Anton, G.
Arends, H. J.
Aulenbacher, K.
Beck, R.
Bradtke, C.
Braghieri, A.
Degrande, N.
d'Hose, N.
Dutz, H.
Goertz, S.
Grabmayr, P.
Hansen, K.
Harmsen, J.
von Harrach, D.
Hasegawa, S.
Hasegawa, T.
Heid, E.
Helbing, Krister
Holvoet, H.
van Hoorebeke, L.
Horikawa, N.
Iwata, T.
Jennewein, P.
Kageya, T.
Kiel, B.
Klein, F.
Kondratiev, R.
Kossert, K.
Krimmer, J.
Lang, M.
Lannoy, B.
Leukel, R.
Lisin, V.
Matsuda, T.
McGeorge, J. C.
Meier, A.
Menze, D.
Meyer, Werner
Michel, Tanja Maria
Naumann, J.
Panzeri, A.
Pedroni, P.
Pinelli, T.
Preobrajenski, I.
Radtke, E.
Reichert, E.
Reicherz, G.
Rohlof, C.
Rosner, G.
Rostomyan, T.
Ryckbosch, D.
Schoch, B.
Schumacher, M.
Seitz, Bjoern
Speckner, T.
Takabayashi, N.
Tamas, Gabor
Thomas, Andy
van de Vyver, R.
Wakai, A.
Weihofen, W.
Wissmann, F.
Zapadtka, F.
Zeitler, G.
DOI
10.1016/j.physletb.2005.08.034
Abstract
The helicity dependence of the total cross section for the (gamma) over right arrow(p) over right arrow -> p pi(0)pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement, performed at the tagged photon beam facility of the MAMI accelerator in Mainz, used the large acceptance detector DAPHNE and a longitudinally polarized frozen-spin target. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, most likely due to the intermediate production of the D-13(1520) resonance. However, the contribution of the antiparallel spin configuration, arising from other reaction mechanisms, is also not negligible. This result gives important new information to resolve the existing model discrepancies in the identification of the nucleon resonances contributing to this channel. (c) 2005 Elsevier B.V. All rights reserved.