The European Physical Journal A (EPJ A)

Eur. Phys. J. A 36, 7-16 (2008)
DOI: 10.1140/epja/i2007-10543-x

Single $\mathrm{\ensuremath{\pi^ }$ production in np collisions for excess energies up to 90 MeV

The COSY-TOF Collaboration, M. Abdel-Bary¹, K. -Th. Brinkmann², H. Clement³, E. Doroshkevich³, S. Dshemuchadse², A. Erhardt³, W. Eyrich⁴, H. Freiesleben², A. Gillitzer¹, R. Jäkel², L. Karsch², K. Kilian¹, E. Kuhlmann², K. Möller⁵, H. P. Morsch^{1, 6}, L. Naumann⁵, N. Paul¹, C. Pizzolotto⁴, J. Ritman¹, E. Roderburg¹, W. Schroeder⁴, M. Schulte-Wissermann², Th. Sefzick¹, A. Teufel⁴, A. Ucar¹, W. Ullrich², P. Wintz¹, P. Wüstner¹ and P. Zupranski⁶

¹ Institut für Kernphysik, Forschungszentrum Jülich, D-52425, Jülich, Germany
² Institut für Kern- und Teilchenphysik, Technische Universität Dresden, D-01062, Dresden, Germany
³ Physikalisches Institut, Universität Tübingen, D-72076, Tübingen, Germany
⁴ Physikalisches Institut, Universität Erlangen, D-91058, Erlangen, Germany
⁵ Institut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, D-01314, Dresden, Germany
⁶ Andrzej Soltan Institute for Nuclear Studies, PL-00681, Warsaw, Poland

e.kuhlmann@physik.tu-dresden.de

(Received 15 August 2007 / Published online 9 April 2008)

Abstract

The quasifree reaction $np\rightarrow pp\ensuremath{\pi^$ was studied in a kinematically complete experiment by bombarding a liquid-hydrogen target with a deuteron beam of momentum 1.85GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector $\mathbb{P} _n$ which differed from event to event. A range of almost 90MeV excess energy above threshold was covered. Energy-dependent angular distributions, invariant-mass spectra as well as fully covered Dalitz plots were deduced. Sizeable pp FSI effects were found as were contributions of p and d partial waves. In comparison with existing literature data the results provide a sensitive test of the spectator model. The behavior of the elementary cross-section σ₀₁ close to threshold is discussed in view of new cross-section data.

PACS
13.75.Cs - Nucleon-nucleon interactions (including antinucleons, deuterons, etc.).
25.10.+s - Nuclear reactions involving few-nucleon systems.

Correspondence: e.kuhlmann@physik.tu-dresden.de

Communicated by P. Braun-Munzinger

Single production in np collisions for excess energies up to 90 MeV

Single $\mathrm{\ensuremath{\pi^ }$ production in np collisions for excess energies up to 90 MeV