Polarization transfer in wide-angle Compton scattering and single-pion photoproduction from the proton

Fanelli, C. et al. (2015) Polarization transfer in wide-angle Compton scattering and single-pion photoproduction from the proton. Physical Review Letters, 115(15), 152001. (doi:10.1103/PhysRevLett.115.152001)

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Abstract

Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θpcm=70°. The longitudinal transfer KLL, measured to be 0.645±0.059±0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ∼3 times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Annand, Dr John and Hamilton, Dr David
Authors: Fanelli, C., Cisbani, E., Hamilton, D.J., Salmé, G., Wojtsekhowski, B., Ahmidouch, A., Annand, J. R. M., Baghdasaryan, H., Beaufait, J., Bosted, P., Brash, E. J., Butuceanu, C., Carter, P., Christy, E., Chudakov, E., Danagoulian, S., Day, D., Degtyarenko, P., Ent, R., Fenker, H., Fowler, M., Frlez, E., Gaskell, D., Gilman, R., Horn, T., Huber, G. M., de Jager, C. W., Jensen, E., Jones, M. K., Kelleher, A., Keppel, C., Khandaker, M., Kohl, M., Kumbartzki, G., Lassiter, S., Li, Y., Lindgren, R., Lovelace, H., Luo, W., Mack, D., Mamyan, V., Margaziotis, D. J., Markowitz, P., Maxwell, J., Mbianda, G., Meekins, D., Meziane, M., Miller, J., Mkrtchyan, A., Mkrtchyan, H., Mulholland, J., Nelyubin, V., Pentchev, L., Perdrisat, C. F., Piasetzky, E., Prok, Y., Puckett, A. J. R., Punjabi, V., Shabestari, M., Shahinyan, A., Slifer, K., Smith, G., Solvignon, P., Subedi, R., Wesselmann, F. R., Wood, S., Ye, Z., and Zheng, X.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review Letters
Publisher:American Physical Society
ISSN:0031-9007
ISSN (Online):1079-7114
Copyright Holders:Copyright © 2015 American Physical Society
First Published:First published in Physical Review Letters 115(15):152001
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
570711Nuclear Physics GroupDavid IrelandScience & Technologies Facilities Council (STFC)ST/J000175/1P&A - PHYSICS & ASTRONOMY