https://doi.org/10.1140/epjc/s10052-011-1609-2
Regular Article - Experimental Physics
Ratios of helicity amplitudes for exclusive ρ 0 electroproduction
1
Physics Division, Argonne National Laboratory, Argonne, IL, 60439-4843, USA
2
Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124, Bari, Italy
3
School of Physics, Peking University, Beijing, 100871, China
4
Nuclear Physics Laboratory, University of Colorado, Boulder, CO, 80309-0390, USA
5
DESY, 22603, Hamburg, Germany
6
DESY, 15738, Zeuthen, Germany
7
Joint Institute for Nuclear Research, 141980, Dubna, Russia
8
Physikalisches Institut, Universität Erlangen-Nürnberg, 91058, Erlangen, Germany
9
Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100, Ferrara, Italy
10
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044, Frascati, Italy
11
Department of Subatomic and Radiation Physics, University of Gent, 9000, Gent, Belgium
12
Physikalisches Institut, Universität Gießen, 35392, Gießen, Germany
13
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
14
Department of Physics, University of Illinois, Urbana, IL, 61801-3080, USA
15
Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI, 48109-1040, USA
16
Lebedev Physical Institute, 117924, Moscow, Russia
17
National Institute for Subatomic Physics (Nikhef), 1009 DB, Amsterdam, The Netherlands
18
St. Petersburg Nuclear Physics Institute, Gatchina, 188300, Leningrad region, Russia
19
Institute for High Energy Physics, Protvino, 142281, Moscow region, Russia
20
Institut für Theoretische Physik, Universität Regensburg, 93040, Regensburg, Germany
21
Istituto Nazionale di Fisica Nucleare, Sezione Roma 1, Gruppo Sanità, Roma, Italy
22
Physics Laboratory, Istituto Superiore di Sanità, 00161, Roma, Italy
23
TRIUMF, Vancouver, British Columbia, V6T 2A3, Canada
24
Department of Physics, Tokyo Institute of Technology, Tokyo, 152, Japan
25
Department of Physics and Astronomy, VU University, 1081 HV, Amsterdam, The Netherlands
26
Andrzej Soltan Institute for Nuclear Studies, 00-689, Warsaw, Poland
27
Yerevan Physics Institute, 375036, Yerevan, Armenia
* e-mail: klaus.rith@desy.de
Received:
17
December
2010
Revised:
2
March
2011
Published online:
2
April
2011
Exclusive ρ
0-meson electroproduction is studied in the HERMES experiment, using a 27.6 GeV longitudinally polarized electron/positron beam and unpolarized hydrogen and deuterium targets in the kinematic region 0.5 GeV2<Q
2<7.0 GeV2, 3.0 GeV <W<6.3 GeV, and −t′<0.4 GeV2. Real and imaginary parts of the ratios of the natural-parity-exchange helicity amplitudes T
11 (
), T
01 (
), T
10 (
), and T
1−1 (
) to T
00 (
) are extracted from the data. For the unnatural-parity-exchange amplitude U
11, the ratio |U
11/T
00| is obtained. The Q
2 and t′ dependences of these ratios are presented and compared with perturbative QCD predictions.
© Springer-Verlag / Società Italiana di Fisica, 2011
