https://doi.org/10.1140/epjc/s10052-015-3341-9
Regular Article - Experimental Physics
Spin density matrix of the 
in the reaction 
Crystal Barrel Collaboration
1
Ruhr-Universität Bochum, 44801, Bochum, Germany
2
Carnegie Mellon University, Pittsburgh, PS, 15213, USA
3
Physik-Institut der Universität Zürich, 8057, Zurich, Switzerland
4
Laboratory for High Energy Physics, Albert Einstein Center for Fundamental Physics, University of Bern, 3012, Bern, Switzerland
5
GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291, Darmstadt, Germany
* e-mail: bertram@ep1.rub.de
Received:
21
October
2014
Accepted:
2
March
2015
Published online:
17
March
2015
The spin density matrix of the has been determined for the reaction with unpolarized in-flight data measured by the Crystal Barrel LEAR experiment at CERN. The two main decay modes of the into 
and 
have been separately analyzed for various 
momenta between 600 and 1940 MeV/c. The results obtained with the usual method by extracting the matrix elements via the decay angular distributions and with the more sophisticated method via a full partial wave analysis are in good agreement. A strong spin alignment of the is clearly visible in this energy regime and all individual spin density matrix elements exhibit an oscillatory dependence on the production angle. In addition, the largest contributing orbital angular momentum of the 
system has been identified for the different beam momenta. It increases from 
2 at 600 MeV/c to
5 at 1940 MeV/c.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
