Phys. Rev. C
77,
042201(R)
(2008)
[5 pages]
Measurement of ep→epπ0 beam spin asymmetries above the resonance region
R. De Masi et al. CLAS Collaboration
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R. De Masi1,30, M. Garçon1, B. Zhao2, M. J. Amaryan29, P. Ambrozewicz12, M. Anghinolfi18, G. Asryan40, H. Avakian35, H. Bagdasaryan29, N. Baillie39, J. Ball1, J. P. Ball4, N. A. Baltzell34, V. Batourine23, M. Battaglieri18, I. Bedlinskiy19, M. Bellis7, N. Benmouna14, B. L. Berman14, P. Bertin20,35, A. S. Biselli7,11, L. Blaszczyk13, S. Bouchigny30, S. Boiarinov35, R. Bradford7, D. Branford10, W. J. Briscoe14, W. K. Brooks35, S. Bültmann29, V. D. Burkert35, C. Butuceanu39, J. R. Calarco26, S. L. Careccia29, D. S. Carman35, L. Casey8, S. Chen13, L. Cheng8, P. L. Cole16, P. Collins4, P. Coltharp13, D. Crabb38, V. Crede13, N. Dashyan40, E. De Sanctis17, R. De Vita18, P. V. Degtyarenko35, A. Deur35, K. V. Dharmawardane29, R. Dickson7, C. Djalali34, G. E. Dodge29, J. Donnelly15, D. Doughty9,35, M. Dugger4, O. P. Dzyubak34, H. Egiyan35, K. S. Egiyan40, L. El Fassi3, L. Elouadrhiri35, P. Eugenio13, G. Fedotov25, G. Feldman14, A. Fradi30, H. Funsten39, G. Gavalian29, G. P. Gilfoyle33, K. L. Giovanetti22, F. X. Girod1,35, J. T. Goetz5, A. Gonenc12, R. W. Gothe34, K. A. Griffioen39, M. Guidal30, N. Guler29, L. Guo35, V. Gyurjyan35, K. Hafidi3, H. Hakobyan40, C. Hanretty13, F. W. Hersman26, K. Hicks28, I. Hleiqawi28, M. Holtrop26, C. E. Hyde-Wright29, Y. Ilieva14, D. G. Ireland15, B. S. Ishkhanov25, E. L. Isupov25, M. M. Ito35, D. Jenkins37, H. S. Jo30, J. R. Johnstone15, K. Joo2, H. G. Juengst14,29, N. Kalantarians29, J. D. Kellie15, M. Khandaker27, W. Kim23, A. Klein29, F. J. Klein8, A. V. Klimenko29, M. Kossov19, Z. Krahn7, L. H. Kramer12,35, V. Kubarovsky31,35, J. Kuhn7, S. E. Kuhn29, S. V. Kuleshov19, J. Lachniet7,29, J. M. Laget35, J. Langheinrich34, D. Lawrence24, T. Lee26, K. Livingston15, H. Y. Lu34, M. MacCormick30, N. Markov2, P. Mattione32, M. Mazouz21, B. McKinnon15, B. A. Mecking35, M. D. Mestayer35, C. A. Meyer7, T. Mibe28, B. Michel20, K. Mikhailov19, M. Mirazita17, R. Miskimen24, V. Mokeev25,35, B. Moreno30, K. Moriya7, S. A. Morrow1,30, M. Moteabbed12, E. Munevar14, G. S. Mutchler32, P. Nadel-Turonski14, R. Nasseripour12,34, S. Niccolai30, G. Niculescu22, I. Niculescu22, B. B. Niczyporuk35, M. R. Niroula29, R. A. Niyazov35, M. Nozar35, M. Osipenko18,25, A. I. Ostrovidov13, K. Park23, E. Pasyuk4, C. Paterson15, S. Anefalos Pereira17, J. Pierce38, N. Pivnyuk19, D. Pocanic38, O. Pogorelko19, S. Pozdniakov19, J. W. Price6, S. Procureur1, Y. Prok35,38, D. Protopopescu15, B. A. Raue12,35, G. Ricco18, M. Ripani18, B. G. Ritchie4, F. Ronchetti17, G. Rosner15, P. Rossi17, F. Sabatié1, J. Salamanca16, C. Salgado27, J. P. Santoro8, V. Sapunenko35, R. A. Schumacher7, V. S. Serov19, Y. G. Sharabian35, D. Sharov25, N. V. Shvedunov25, E. S. Smith35, L. C. Smith38, D. I. Sober8, D. Sokhan10, A. Stavinsky19, S. Stepanyan35, S. S. Stepanyan23, B. E. Stokes13, P. Stoler31, I. I. Strakovsky14, S. Strauch14,34, M. Taiuti18, D. J. Tedeschi34, A. Tkabladze14,28, S. Tkachenko29, C. Tur34, M. Ungaro2, M. F. Vineyard36, A. V. Vlassov19, E. Voutier21, D. P. Watts15, L. B. Weinstein29, D. P. Weygand35, M. Williams7, E. Wolin35, M. H. Wood34, A. Yegneswaran35, L. Zana26, J. Zhang29, and Z. W. Zhao34 (CLAS Collaboration)
1CEA-Saclay, Service de Physique Nucléaire, F-91191 Gif-sur-Yvette, France
2University of Connecticut, Storrs, Connecticut 06269, USA
3Argonne National Laboratory, Argonne, Illinois 60439, USA
4Arizona State University, Tempe, Arizona 85287-1504, USA
5University of California at Los Angeles, Los Angeles, California 90095-1547, USA
6California State University, Dominguez Hills, Carson, California 90747, USA
7Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
8Catholic University of America, Washington, D. C. 20064, USA
9Christopher Newport University, Newport News, Virginia 23606, USA
10Edinburgh University, Edinburgh EH9 3JZ, United Kingdom
11Fairfield University, Fairfield, Connecticut 06824, USA
12Florida International University, Miami, Florida 33199, USA
13Florida State University, Tallahassee, Florida 32306, USA
14The George Washington University, Washington, D. C. 20052, USA
15University of Glasgow, Glasgow G12 8QQ, United Kingdom
16Idaho State University, Pocatello, Idaho 83209, USA
17INFN, Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
18INFN, Sezione di Genova, I-16146 Genova, Italy
19Institute of Theoretical and Experimental Physics, Moscow RU-117259, Russia
20LPC Clermont-Ferrand, Université Blaise Pascal, CNRS/IN2P3, F-63177 Aubière, France
21LPSC, Université Joseph Fourier, CNRS/IN2P3, INPG, F-38026 Grenoble, France
22James Madison University, Harrisonburg, Virginia 22807, USA
23Kyungpook National University, Daegu 702-701, South Korea
24University of Massachusetts, Amherst, Massachusetts 01003, USA
25Moscow State University, General Nuclear Physics Institute, RU-119899 Moscow, Russia
26University of New Hampshire, Durham, New Hampshire 03824-3568, USA
27Norfolk State University, Norfolk, Virginia 23504, USA
28Ohio University, Athens, Ohio 45701, USA
29Old Dominion University, Norfolk, Virginia 23529, USA
30Institut de Physique Nucléaire, F-91406 Orsay, France
31Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA
32Rice University, Houston, Texas 77005-1892, USA
33University of Richmond, Richmond, Virginia 23173, USA
34University of South Carolina, Columbia, South Carolina 29208, USA
35Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
36Union College, Schenectady, New York 12308, USA
37Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0435, USA
38University of Virginia, Charlottesville, Virginia 22901, USA
39College of William and Mary, Williamsburg, Virginia 23187-8795, USA
40Yerevan Physics Institute, 375036 Yerevan, Armenia
Received 4 December 2007; published 14 April 2008
The beam spin asymmetry (BSA) in the exclusive reaction e⃗p→epπ0 was measured with the CEBAF 5.77 GeV polarized electron beam and Large Acceptance Spectrometer (CLAS). The xB,Q2,t, and ϕ dependences of the π0 BSA are presented in the deep inelastic regime. The asymmetries are fitted with a sinϕ function and their amplitudes are extracted. Overall, they are of the order of 0.04–0.11 and roughly independent of t. This is the signature of a nonzero longitudinal-transverse interference. The implications concerning the applicability of a formalism based on generalized parton distributions, as well as the extension of a Regge formalism at high photon virtualities, are discussed.
© 2008 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevC.77.042201
DOI:
10.1103/PhysRevC.77.042201
PACS:
12.40.Vv, 13.40.Gp, 13.60.Hb, 13.60.Le
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