Eur. Phys. J. A (2009) 39: 281-289
https://doi.org/10.1140/epja/i2008-10721-4

Regular Article - Experimental Physics

Single-pion production in pp collisions at 0.95 GeV/c (II)

¹ Ruhr-Universität Bochum, Bochum, Germany
² Technische Universität Dresden, Dresden, Germany
³ Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen-Nürnberg, Germany
⁴ Forschungszentrum Jülich, Jülich, Germany
⁵ Forschungszentrum Rossendorf, Dresden, Germany
⁶ Physikalisches Institut der Universität Tübingen, Tübingen, Germany
⁷ University of Torino and INFN, Sezione di Torino, Torino, Italy
⁸ Atomic Energy Authority NRC Cairo, Cairo, Egypt
⁹ Soltan Institute for Nuclear Studies, Warsaw, Poland

^* e-mail: clement@pit.physik.uni-tuebingen.de

Received: 8 July 2008
Revised: 3 December 2008
Accepted: 14 January 2009
Published online: 13 February 2009

Abstract

The single-pion production reactions pp d , pp np and pp pp were measured at a beam momentum of 0.95GeV/c ( T _p 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and discussion of the np channel, since the results on the other channels have already been published previously. The total and differential cross-sections obtained are compared to theoretical calculations. In contrast to the pp channel we observe in the np channel a strong influence of the excitation. In particular, the pion angular distribution exhibits a (3 cos² + 1) -dependence, typical for a pure s -channel excitation and identical to that observed in the d channel. Since the latter is understood by a s -channel resonance in the ¹ D ₂ pn partial wave, we discuss an analogous scenario for the pn channel.