Eur. Phys. J. A (2013) 49: 132
https://doi.org/10.1140/epja/i2013-13132-6

Regular Article - Experimental Physics

In-medium modifications of the ω meson near the production threshold

¹ II. Physikalisches Institut, University of Gießen, D-35392, Giessen, Germany
² Institut für Kernphysik, University of Mainz, D-55099, Mainz, Germany
³ SUPA, School of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
⁴ Kent State University, 44242, Kent, Ohio, USA
⁵ Helmholtz-Institut für Strahlen- und Kernphysik, University Bonn, D-53115, Bonn, Germany
⁶ Petersburg Nuclear Physics Institute, RU-188300, Gatchina, Russia
⁷ INFN Sezione di Pavia, I-27100, Pavia, Italy
⁸ Center for Nuclear Studies, The George Washington University, 20052, Washington, DC, USA
⁹ University of California Los Angeles, 90095-1547, Los Angeles, California, USA
¹⁰ Lebedev Physical Institute, RU-119991, Moscow, Russia
¹¹ Department of Physics, University of Basel, Ch-4056, Basel, Switzerland
¹² SUPA, School of Physics, University of Edingburgh, EH9 3JZ, Edinburgh, UK
¹³ Mount Allison University, E4L1E6, New Brunswick, Canada
¹⁴ Institute for Nuclear Research, RU-125047, Moscow, Russia
¹⁵ Rudjer Boskovic Institute, HR-10000, Zagreb, Croatia
¹⁶ II. Physikalisches Institut, University of Göttingen, D-37077, Göttingen, Germany
¹⁷ University of Massachusetts Amherst, 01003, Amherst, MA, USA
¹⁸ Institut für Theoretische Physik, University of Gießen, D-35392, Giessen, Germany

^* e-mail: thiel@kph.uni-mainz.de

Received: 29 May 2013
Revised: 22 September 2013
Accepted: 24 September 2013
Published online: 23 October 2013

Abstract

The in-medium properties of the ω meson were investigated at the MAMI-C electron accelerator using the Crystal Ball/TAPS detector system to identify ω mesons through their ω → π ⁰ γ decay channel. Two solid targets (C, Nb) and a LH₂ target as a reference have been used. In the energy range 900 to 1300 MeV the ω lineshapes for the different nuclei are compared and a broadening of the ω signal for the niobium target is observed in comparison to the liquid-hydrogen target. In a second analysis the ω momentum distributions for the solid targets are determined for 50 MeV/c wide bins. For both analyses a comparison to transport calculations shows that the data are consistent with an in-medium modification by collisional broadening, as observed by transparency ratio measurements.