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

Ye.S. Golubeva; L.A. Kondratyuk; M. Büscher; W. Cassing; V. Hejny; H. Ströher

doi:doi:10.1007/s100500170088

2021 Impact factor 3.131

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