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Production of the 1S0 diproton in the pp -> pp pi0 reaction at 0.8 GeV

S. Dymov, D. Gusev, M. Hartmann, V. Hejny, A. Kacharava, A. Khoukaz, V. Komarov, P. Kulessa, A. Kulikov, V. Kurbatov, N. Lang, G. Macharashvili, T. Mersmann, S. Merzliakov, S. Mikirtytchiants, A. Mussgiller, D. Prasuhn, F. Rathmann, R. Schleichert, H. Stroeher, Yu. Uzikov, C. Wilkin, S. Yaschenko

nucl-exarXiv:nucl-ex/0512035

Abstract

The pp -> pp pi0 differential cross section has been measured with the ANKE spectrometer at COSY-Juelich for pion cms angles between 0 and 15.4 degrees at a proton beam energy of 0.8 GeV. The selection of diproton pairs with an excitation energy Epp < 3 MeV ensures that the final pp system is dominantly in the spin-singlet 1S0 state. The kinematics are therefore very similar to those of pp -> d pi+ but with different spin and isospin transitions. The results will thus provide a crucial extra test of pion production models in nucleon-nucleon collisions. The cross sections, which are over two orders of magnitude smaller than those of pp -> d pi+, show a forward dip, even stronger than that seen at lower energies. This behaviour is well reproduced in a theoretical model that includes P-wave Delta-N states.

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