Eur. Phys. J. A (2016) 52: 297
https://doi.org/10.1140/epja/i2016-16297-4

Regular Article - Experimental Physics

Momentum dependence of the imaginary part of the - and -nucleus optical potential

¹ II. Physikalisches Institut, Universität Gießen, Gießen, Germany
² Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Bonn, Germany
³ Petersburg Nuclear Physics Institute, Gatchina, Russia
⁴ Physikalisches Institut, Universität Bonn, Bonn, Germany
⁵ Department of Physics, Florida State University, Tallahassee, FL, USA
⁶ Departement Physik, Universität Basel, Basel, Switzerland
⁷ Physikalisches Institut, Universität Bochum, Bochum, Germany

^* e-mail: Mariana.Nanova@exp2.physik.uni-giessen.de

Received: 3 May 2016
Accepted: 23 August 2016
Published online: 27 September 2016

Abstract

The photoproduction of and mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9GeV at the electron accelerator ELSA. The mesons have been identified via the and decays, respectively, registered with the CBELSA/TAPS detector system. From the measured meson momentum distributions the momentum dependence of the transparency ratio has been determined for both mesons. Within a Glauber analysis the in-medium and widths and the corresponding absorption cross sections have been deduced as a function of the meson momentum. The results are compared to recent theoretical predictions for the in-medium width and -N absorption cross sections. The energy dependence of the imaginary part of the - and -nucleus optical potential has been extracted. The finer binning of the present data compared to the existing data allows a more reliable extrapolation towards the production threshold. The modulus of the imaginary part of the -nucleus potential is found to be about three times smaller than recently determined values of the real part of the -nucleus potential, which makes the meson a suitable candidate for the search for meson-nucleus bound states. For the meson, the modulus of the imaginary part near threshold is comparable to the modulus of the real part of the potential. As a consequence, only broad structures can be expected, which makes the observation of mesic states very difficult experimentally.