https://doi.org/10.1140/epja/i2011-11108-2
Regular Article - Experimental Physics
Exclusive measurement of the pp → nnπ+π+ reaction at 1.1 GeV
1
Physikalisches Institut, Universität Tübingen, D-72076, Tübingen, Germany
2
Kepler Center for Astro and Particle Physics, University of Tübingen, D-72076, Tübingen, Germany
3
Joint Institute for Nuclear Research, 141980, Dubna, Russia
4
The Svedberg Laboratory, Uppsala University, 75121, Uppsala, Sweden
5
Institut für Experimentalphysik, Hamburg University, 22761, Hamburg, Germany
6
Department of Physics and Astronomy, Uppsala University, 75120, Uppsala, Sweden
7
Institut für Kernphysik, Forschungszentrum Jülich, 52425, Jülich, Germany
8
Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia
9
The Andrzej Soltan Institute for Nuclear Studies, 00-681, Warsaw, Poland
10
Physics Department, Stockholm University, 10691, Stockholm, Sweden
11
High Energy Accelerator Research Organization, Tsukuba, Japan
12
90-950, Lodz, Poland
* e-mail: clement@pit.physik.uni-tuebingen.de
Received:
19
July
2011
Accepted:
13
September
2011
Published online:
22
September
2011
First exclusive data for the 
reaction have been obtained at CELSIUS with the WASA detector setup at a beam energy of Tp = 1.1 GeV. Total and differential cross-sections disagree with theoretical calculations, which predict the 
excitation to be the dominant process at this beam energy. Instead, the data require the excitation of one of the nucleons to a higher-lying state, preferably the 
, to be the leading process.
© SIF, Springer-Verlag Berlin Heidelberg, 2011
