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Ratios of helicity amplitudes for exclusive ρ⁰ electroproduction on transversely polarized protons

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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.
Keywords
VECTOR-MESON PRODUCTION, GENERALIZED PARTON DISTRIBUTIONS, CROSS-SECTION, ELASTIC ELECTROPRODUCTION, J/PSI MESONS, HERA, SCATTERING, SPIN, LEPTOPRODUCTION, HYDROGEN

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MLA
Airapetian, A et al. “Ratios of Helicity Amplitudes for Exclusive Ρ0 Electroproduction on Transversely Polarized Protons.” EUROPEAN PHYSICAL JOURNAL C 77.6 (2017): n. pag. Print.
APA
Airapetian, A., Akopov, N., Akopov, Z., Aschenauer, E., Augustyniak, W., Belostotski, S., Blok, H., et al. (2017). Ratios of helicity amplitudes for exclusive ρ0 electroproduction on transversely polarized protons. EUROPEAN PHYSICAL JOURNAL C, 77(6).
Chicago author-date
Airapetian, A, N Akopov, Z Akopov, EC Aschenauer, W Augustyniak, S Belostotski, HP Blok, et al. 2017. “Ratios of Helicity Amplitudes for Exclusive Ρ0 Electroproduction on Transversely Polarized Protons.” European Physical Journal C 77 (6).
Chicago author-date (all authors)
Airapetian, A, N Akopov, Z Akopov, EC Aschenauer, W Augustyniak, S Belostotski, HP Blok, A Borissov, V Bryzgalov, GP Capitani, G Ciullo, M Contalbrigo, W Deconinck, R De Leo, E De Sanctis, M Duren, G Elbakian, F Ellinghaus, L Felawka, S Frullani, F Garibaldi, G Gavrilov, V Gharibyan, SV Goloskokov, Y Holler, A Ivanilov, HE Jackson, Sylvester Joosten, R Kaiser, G Karyan, A Kisselev, V Korotkov, V Kozlov, P Kravchenko, P Kroll, L Lagamba, L Lapikas, I Lehmann, P Lenisa, W Lorenzon, SI Manaenkov, B Marianski, H Marukyan, Y Miyachi, A Movsisyan, V Muccifora, A Nass, W-D Nowak, LL Pappalardo, A Petrosyan, PE Reimer, R Reolon, C Riedl, K Rith, G Rosner, A Rostomyan, Dirk Ryckbosch, Y Salomatin, A Schaefer, Gunar Schnell, B Seitz, T-A Shibata, V Shutov, M Statera, A Terkulov, R Truty, A Trzcinski, Michael Tytgat, Yves Van Haarlem, Charlotte Van Hulse, D Veretennikov, V Vikhrov, I Vilardi, S Yaschenko, B Zihlmann, and P Zupranski. 2017. “Ratios of Helicity Amplitudes for Exclusive Ρ0 Electroproduction on Transversely Polarized Protons.” European Physical Journal C 77 (6).
Vancouver
1.
Airapetian A, Akopov N, Akopov Z, Aschenauer E, Augustyniak W, Belostotski S, et al. Ratios of helicity amplitudes for exclusive ρ0 electroproduction on transversely polarized protons. EUROPEAN PHYSICAL JOURNAL C. 2017;77(6).
IEEE
[1]
A. Airapetian et al., “Ratios of helicity amplitudes for exclusive ρ0 electroproduction on transversely polarized protons,” EUROPEAN PHYSICAL JOURNAL C, vol. 77, no. 6, 2017.
@article{8565617,
  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.},
  articleno    = {378},
  author       = {Airapetian, A and Akopov, N and Akopov, Z and Aschenauer, EC and Augustyniak, W and Belostotski, S and Blok, HP and Borissov, A and Bryzgalov, V and Capitani, GP and Ciullo, G and Contalbrigo, M and Deconinck, W and De Leo, R and De Sanctis, E and Duren, M and Elbakian, G and Ellinghaus, F and Felawka, L and Frullani, S and Garibaldi, F and Gavrilov, G and Gharibyan, V and Goloskokov, SV and Holler, Y and Ivanilov, A and Jackson, HE and Joosten, Sylvester and Kaiser, R and Karyan, G and Kisselev, A and Korotkov, V and Kozlov, V and Kravchenko, P and Kroll, P and Lagamba, L and Lapikas, L and Lehmann, I and Lenisa, P and Lorenzon, W and Manaenkov, SI and Marianski, B and Marukyan, H and Miyachi, Y and Movsisyan, A and Muccifora, V and Nass, A and Nowak, W-D and Pappalardo, LL and Petrosyan, A and Reimer, PE and Reolon, R and Riedl, C and Rith, K and Rosner, G and Rostomyan, A and Ryckbosch, Dirk and Salomatin, Y and Schaefer, A and Schnell, Gunar and Seitz, B and Shibata, T-A and Shutov, V and Statera, M and Terkulov, A and Truty, R and Trzcinski, A and Tytgat, Michael and Van Haarlem, Yves and Van Hulse, Charlotte and Veretennikov, D and Vikhrov, V and Vilardi, I and Yaschenko, S and Zihlmann, B and Zupranski, P},
  issn         = {1434-6044},
  journal      = {EUROPEAN PHYSICAL JOURNAL C},
  keywords     = {VECTOR-MESON PRODUCTION,GENERALIZED PARTON DISTRIBUTIONS,CROSS-SECTION,ELASTIC ELECTROPRODUCTION,J/PSI MESONS,HERA,SCATTERING,SPIN,LEPTOPRODUCTION,HYDROGEN},
  language     = {eng},
  number       = {6},
  pages        = {23},
  title        = {Ratios of helicity amplitudes for exclusive ρ⁰ electroproduction on transversely polarized protons},
  url          = {http://dx.doi.org/10.1140/epjc/s10052-017-4899-1},
  volume       = {77},
  year         = {2017},
}

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