Eur. Phys. J. A (2014) 50: 79
https://doi.org/10.1140/epja/i2014-14079-8

Regular Article - Experimental Physics

Measurement of radiative widths of a₂(1320) and (1670)

¹ Universität Bielefeld, Fakultät für Physik, 33501, Bielefeld, Germany
² Universität Bochum, Institut für Experimentalphysik, 44780, Bochum, Germany
³ Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115, Bonn, Germany
⁴ Universität Bonn, Physikalisches Institut, 53115, Bonn, Germany
⁵ Institute of Scientific Instruments, AS CR, 61264, Brno, Czech Republic
⁶ Matrivani Institute of Experimental Research & Education, 700 030, Calcutta, India
⁷ Joint Institute for Nuclear Research, 141980, Dubna, Russia
⁸ Universität Erlangen-Nürnberg, Physikalisches Institut, 91054, Erlangen, Germany
⁹ Universität Freiburg, Physikalisches Institut, 79104, Freiburg, Germany
¹⁰ CERN, 1211, Geneva 23, Switzerland
¹¹ Technical University in Liberec, 46117, Liberec, Czech Republic
¹² LIP, 1000-149, Lisbon, Portugal
¹³ Universität Mainz, Institut für Kernphysik, 55099, Mainz, Germany
¹⁴ University of Miyazaki, 889-2192, Miyazaki, Japan
¹⁵ Lebedev Physical Institute, 119991, Moscow, Russia
¹⁶ Ludwig-Maximilians-Universität München, Department für Physik, 80799, Munich, Germany
¹⁷ Technische Universität München, Physik Department, 85748, Garching, Germany
¹⁸ Nagoya University, 464, Nagoya, Japan
¹⁹ Charles University in Prague, Faculty of Mathematics and Physics, 18000, Prague, Czech Republic
²⁰ Czech Technical University in Prague, 16636, Prague, Czech Republic
²¹ State Scientific Center Institute for High Energy Physics of National Research Center “Kurchatov Institute”, 142281, Protvino, Russia
²² CEA IRFU/SPhN Saclay, 91191, Gif-sur-Yvette, France
²³ Tel Aviv University, School of Physics and Astronomy, 69978, Tel Aviv, Israel
²⁴ Trieste Section of INFN, 34127, Trieste, Italy
²⁵ University of Trieste, Department of Physics, 34127, Trieste, Italy
²⁶ Abdus Salam ICTP, 34151, Trieste, Italy
²⁷ University of Turin, Department of Physics, 10125, Turin, Italy
²⁸ Torino Section of INFN, 10125, Turin, Italy
²⁹ University of Eastern Piedmont, 15100, Alessandria, Italy
³⁰ National Centre for Nuclear Research, 00-681, Warsaw, Poland
³¹ University of Warsaw, Faculty of Physics, 00-681, Warsaw, Poland
³² Warsaw University of Technology, Institute of Radioelectronics, 00-665, Warsaw, Poland
³³ Yamagata University, 992-8510, Yamagata, Japan

Received: 13 March 2014
Accepted: 24 March 2014
Published online: 25 April 2014

Abstract

The COMPASS Collaboration at CERN has investigated the reaction embedded in the Primakoff reaction of 190 GeV pions scattering in the Coulomb field of a lead target, . Exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at momentum transfer below 0.001 (GeV/c)². Using a partial-wave analysis the amplitudes and relative phases of the and mesons have been extracted, and the Coulomb and the diffractive contributions have been disentangled. Measuring absolute production cross sections we have determined the radiative width of the to be keV. As the first measurement, is obtained for the radiative width of the , where in this analysis the branching ratio has been used. We compare these values to previous measurements and theoretical predictions.