EPJ

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EPJ A - Hadrons and Nuclei
Hadrons and Nuclei


Eur. Phys. J. A 11, 237-245 (2001)

Medium effects in the production and ${\pi^0 \gamma}$ decay of ${\omega}$-mesons in pA collisions in the GeV region

Ye.S. Golubeva1, L.A. Kondratyuk2, M. Büscher3, W. Cassing4, V. Hejny3 and H. Ströher3

1  Institute of Nuclear Research, 117312 Moscow, Russia
2  Institute of Theoretical and Experimental Physics, 117259 Moscow, Russia
3  Forschungszentrum Jülich, Institut für Kernphysik, 52425 Jülich, Germany
4  Institute for Theoretical Physics, University of Giessen, D-35392 Giessen, Germany

m.buescher@fz-juelich.de

(Received: 2 April 2001 / Revised version: 23 May 2001 Communicated by A. Schäfer)

Abstract
The ${\omega}$ resonance production and its ${\pi^0 \gamma}$ decay in pA reactions close to threshold is considered within the Intranuclear Cascade (INC) model. The ${\pi^0 \gamma}$ invariant-mass distribution shows two components which correspond to the ${\omega}$ decay "inside" and "outside" the nucleus, respectively. The "inside" component is distorted by medium effects, which introduce a mass shift as well as collisional broadening for the ${\omega}$-meson and its decaying pion. The relative contribution of the "inside" component is analyzed in detail for different kinematical conditions and nuclear targets. It is demonstrated that a measurement of the correlation in azimuthal angle between the $\pi^0$ and $\gamma$ momenta allows to separate events related to the "inside" ${\omega}$ decay from different sources of background when uncorrelated $\pi^0$'s and $\gamma$'s are produced.

PACS
25.40.Ep - Inelastic proton scattering.
25.80.-e - Meson- and hyperon-induced reactions.
25.80.Ek - Pion inelastic scattering.

© Società Italiana di Fisica, Springer-Verlag 2001

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