Beam-helicity asymmetry arising from deeply virtual Compton scattering measured with kinematically complete event reconstruction

A bstract The beam-helicity asymmetry in exclusive electroproduction of real photons by the longitudinally polarized Hera positron beam scattering off an unpolarized hydrogen target is measured at Hermes. The asymmetry arises from deeply virtual Compton scattering and its interference with the Bethe...

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Veröffentlicht in:	The journal of high energy physics 2012-10, Vol.2012 (10), Article 42
Hauptverfasser:	Akopov, N., Akopov, Z., Augustyniak, W., Avetissian, A., Avetisyan, E., Belostotski, S., Blok, H. P., Borissov, A., Bowles, J., Brodski, I., Bryzgalov, V., Burns, J., Capitani, G. P., Cisbani, E., Ciullo, G., Contalbrigo, M., Deconinck, W., De Leo, R., De Nardo, L., Di Nezza, P., Düren, M., Ehrenfried, M., Elbakian, G., Fabbri, R., Fantoni, A., Felawka, L., Frullani, S., Gapienko, G., Garibaldi, F., Gavrilov, G., Giordano, F., Gliske, S., Golembiovskaya, M., Gregor, I. M., Guler, H., Hartig, M., Hasch, D., Hillenbrand, A., Hoek, M., Holler, Y., Ivanilov, A., Joosten, S., Kaiser, R., Karyan, G., Kisselev, A., Kozlov, V., Krauss, B., Kravchenko, P., Lagamba, L., Lapikás, L., Lehmann, I., Lenisa, P., Ruiz, A. López, Lorenzon, W., Lu, S., Lu, X., Ma, B.-Q., Mahon, D., Manaenkov, S. I., Marianski, B., de la Ossa, A. Martinez, Movsisyan, A., Murray, M., Mussgiller, A., Nappi, E., Nass, A., Negodaev, M., Osborne, A., Perez-Benito, R., Petrosyan, A., Reimer, P. E., Reolon, A. R., Rith, K., Rostomyan, A., Rubacek, L., Rubin, J., Ryckbosch, D., Schäfer, A., Schnell, G., Schüler, K. P., Shibata, T.-A., Shutov, V., Statera, M., Stewart, J., Taroian, S., Terkulov, A., Truty, R., Trzcinski, A., Tytgat, M., Van Haarlem, Y., Van Hulse, C., Veretennikov, D., Vikhrov, V., Vilardi, I., Wang, S., Yaschenko, S., Yen, S., Zeiler, D., Zihlmann, B., Zupranski, P.
Format:	Artikel
Sprache:	eng
Schlagworte:	Amplitudes Asymmetry Classical and Quantum Gravitation Elastic scattering Elementary Particles Helicity High energy physics Physics Physics and Astronomy Positron beams Quantum Field Theories Quantum Field Theory Quantum Physics Recoil Relativity Theory String Theory
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Zusammenfassung:	A bstract The beam-helicity asymmetry in exclusive electroproduction of real photons by the longitudinally polarized Hera positron beam scattering off an unpolarized hydrogen target is measured at Hermes. The asymmetry arises from deeply virtual Compton scattering and its interference with the Bethe-Heitler process. Azimuthal amplitudes of the beam-helicity asymmetry are extracted from a data sample consisting of ep → epγ events with detection of all particles in the final state including the recoiling proton. The installation of a recoil detector, while reducing the acceptance of the experiment, allows the elimination of background from ep → eN πγ events, which was estimated to contribute an average of about 12% to the signal in previous Hermes publications. The removal of this background from the present data sample is shown to increase the magnitude of the leading asymmetry amplitude by 0 . 054 ± 0 . 016 to −0 . 328 ± 0 . 027 (stat . ) ± 0 . 045 (syst . ).
ISSN:	1029-8479 1029-8479
DOI:	10.1007/JHEP10(2012)042