Eur. Phys. J. A (2013) 49: 65
https://doi.org/10.1140/epja/i2013-13065-0

Regular Article - Experimental Physics

Measurements of ¹²C photon asymmetries for –450 MeV

¹ SUPA, School of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
² Institut für Kernphysik, University of Mainz, D-55099, Mainz, Germany
³ Petersburg Nuclear Physics Institute, 188300, Gatchina, Russia
⁴ Kent State University, 44242, Kent, Ohio, USA
⁵ Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, D-53115, Bonn, Germany
⁶ II Physikalisches Institut, University of Giessen, D-35392, Giessen, Germany
⁷ INFN Sezione di Pavia, I-27100, Pavia, Italy
⁸ SUPA, School of Physics, University of Edinburgh, EH9 3JZ, Edinburgh, UK
⁹ The George Washington University, 20052, Washington, DC, USA
¹⁰ University of California Los Angeles, 90095-1547, Los Angeles, California, USA
¹¹ Lebedev Physical Institute, 119991, Moscow, Russia
¹² Institut für Physik, University of Basel, CH-4056, Basel, Switzerland
¹³ Mount Allison University, E4L3B5, Sackville, New Brunswick, Canada
¹⁴ Institute for Nuclear Research, 125047, Moscow, Russia
¹⁵ Rudjer Boskovic Institute, HR-10000, Zagreb, Croatia
¹⁶ The Catholic University of America, DC 20064, Washington, USA

^* e-mail: douglas.macgregor@glasgow.ac.uk

Received: 2 April 2013
Revised: 9 May 2013
Accepted: 14 May 2013
Published online: 30 May 2013

Abstract

The ¹²C reaction has been studied in the photon energy range 200-450 MeV at the Mainz microtron MAMI-C, where linearly polarised photons were energy-tagged using the Glasgow-Mainz Tagged Photon Spectrometer and protons were detected in the Crystal Ball detector. The photon asymmetry has been measured over a wider range than previous measurements. The strongest asymmetries were found at low missing energies where direct emission of nucleon pairs is expected. Cuts on the difference in azimuthal angles of the two ejected protons increased the magnitude of the observed asymmetries. At low missing energies the data exhibit a strong angular dependence, similar to deuteron photodisintegration.