




Item type: | Article | ||||
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Journal or Publication Title: | The European Physical Journal C | ||||
Publisher: | Springer | ||||
Place of Publication: | NEW YORK | ||||
Volume: | 77 | ||||
Number of Issue or Book Chapter: | 6 | ||||
Date: | 2017 | ||||
Institutions: | Physics > Institute of Theroretical Physics | ||||
Identification Number: |
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Keywords: | VECTOR-MESON PRODUCTION; GENERALIZED PARTON DISTRIBUTIONS; CROSS-SECTION; ELASTIC ELECTROPRODUCTION; J/PSI MESONS; HERA; SCATTERING; SPIN; LEPTOPRODUCTION; HYDROGEN; | ||||
Dewey Decimal Classification: | 500 Science > 530 Physics | ||||
Status: | Published | ||||
Refereed: | Yes, this version has been refereed | ||||
Created at the University of Regensburg: | Yes | ||||
Item ID: | 38896 |

Abstract
Exclusive rho(0)-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV2 < Q(2) < 7.0GeV(2), 3.0GeV< W < 6.3 GeV, and -t' < 0.4 GeV2. Using an unbinned maximum-likelihood method, 25 parameters are extracted. These determine the real and ...

Abstract
Exclusive rho(0)-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV2 < Q(2) < 7.0GeV(2), 3.0GeV< W < 6.3 GeV, and -t' < 0.4 GeV2. Using an unbinned maximum-likelihood method, 25 parameters are extracted. These determine the real and imaginary parts of the ratios of several helicity amplitudes describing rho(0)-meson production by a virtual photon. The denominator of those ratios is the dominant amplitude, the nucleon-helicity-non-flip amplitude F-0 (1/2 0 1/2), which describes the production of a longitudinal rho(0)-meson by a longitudinal virtual photon. The ratios of nucleon-helicity-nonflip amplitudes are found to be in good agreement with those from the previous HERMES analysis. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to F-0 (1/2 0 1/2). Results obtained in a handbag approach based on generalized parton distributions taking into account the contribution from pion exchange are found to be in good agreement with these ratios. Within the model, the data favor a positive sign for the pi - rho transition form factor. By also exploiting the longitudinal beam polarization, a total of 71.0 spin-density matrix elements is determined from the extracted 25 parameters, in contrast to only 53 elements as directly determined in earlier analyses.
Metadata last modified: 25 Nov 2020 15:45