Phys. Rev. Lett.
87,
182002
(2001)
[5 pages]
Observation of Exclusive Deeply Virtual Compton Scattering in Polarized Electron Beam Asymmetry Measurements
S. Stepanyan et al. (CLAS Collaboration)
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S. Stepanyan1,2, V. D. Burkert2, L. Elouadrhiri1,2, G. S. Adams28, E. Anciant7, M. Anghinolfi15, B. Asavapibhop20, G. Audit7, T. Auger7, H. Avakian14, J. Ball3, S. Barrow13, M. Battaglieri15, K. Beard18, M. Bektasoglu25, P. Bertin9, N. Bianchi14, A. Biselli28, S. Boiarinov17, B. E. Bonner29, S. Bouchigny2,26, D. Branford11, W. K. Brooks2, J. R. Calarco22, D. S. Carman24, B. Carnahan6, L. Ciciani25, P. L. Cole32,2, A. Coleman35,*, D. Cords2, P. Corvisiero15, D. Crabb33, H. Crannell6, J. Cummings28, P. V. Degtiarenko2, H. Denizli27, L. C. Dennis13, E. De Sanctis14, R. DeVita15, K. V. Dharmawardane25, C. Djalali31, G. E. Dodge25, D. Doré7, D. Doughty1,2, P. Dragovitsch13, S. Dytman27, M. Eckhause35, H. Egiyan35, K. S. Egiyan36, A. Empl28, R. Fatemi33, R. J. Feuerbach5, J. Ficenec34, K. Fissum21, T. A. Forest25, A. P. Freyberger25, H. Funsten35, S. Gaff10, M. Gai8, M. Garçon7, G. Gavalian36,†, S. Gilad21, G. P. Gilfoyle30, K. Giovanetti18, P. Girard31, K. A. Griffioen35, M. Guidal26, M. Guillo31, V. Gyurjyan2, C. Hadjidakis26, J. Hardie1,2, D. Heddle1,2, F. W. Hersman22, K. Hicks24, R. S. Hicks20, M. Holtrop22, J. Hu28, C. E. Hyde-Wright25, M. M. Ito2, D. Jenkins34, K. Joo33,‡, J. Kelley10, M. Khandaker23, D. H. Kim19, K. Kim19, K. Y. Kim27, W. Kim19, A. Klein25, F. J. Klein2, M. Klusman28, M. Kossov17, L. H. Kramer12,2, S. E. Kuhn25, J. M. Laget7, D. Lawrence20, A. Longhi6, K. Lukashin32,2,§, J. J. Manak2,**, C. Marchand7, S. McAleer13, J. McCarthy33, J. W. C. McNabb5, B. A. Mecking2, M. D. Mestayer2, C. A. Meyer5, K. Mikhailov17, R. Minehart33, M. Mirazita14, R. Miskimen20, L. Morand7, V. Muccifora14, J. Mueller27, G. S. Mutchler29, J. Napolitano28, S. Nelson10, S. Niccolai16, G. Niculescu24, I. Niculescu16, R. A. Niyazov25, A. Opper24, G. O'Rielly16, J. T. O'Brien6, K. Park19, E. Pasyuk3, G. A. Peterson20, S. Philips16, N. Pivnyuk17, D. Pocanic33, O. Pogorelko17, E. Polli14, I. Popa16, S. Pozdniakov17, B. M. Preedom31, J. W. Price31, D. Protopopescu22, L. M. Qin25, B. A. Raue12,2, A. R. Reolon14, G. Riccardi13, G. Ricco15, M. Ripani15, B. G. Ritchie3, F. Ronchetti14, P. Rossi14, D. Rowntree21, P. D. Rubin30, F. Sabatié7,25, K. Sabourov10, C. W. Salgado23,2, V. Sapunenko15, R. A. Schumacher5, V. Serov17, Y. G. Sharabian36,2, J. Shaw20, S. Simionatto16, A. Skabelin21, E. S. Smith2, L. C. Smith33, D. I. Sober6, A. Stavinsky17, P. Stoler28, I. I. Strakovsky16, R. Suleiman21, M. Taiuti15, S. Taylor29, D. Tedeschi31,2, R. Thompson27, L. Todor5, M. F. Vineyard30, A. Vlassov17, K. Wang33, H. Weller10, L. B. Weinstein25, R. Welsh35, D. P. Weygand2, S. Whisnant31, E. Wolin2, A. Yegneswaran2, J. Yun25, J. Zhao21, B. Zhang21, and Z. Zhou21 (CLAS Collaboration)
1Christopher Newport University, Newport News, Virginia 23606
2Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606
3Arizona State University, Department of Physics and Astronomy, Tempe, Arizona 85287
4University of California at Los Angeles, Department of Physics and Astronomy, Los Angeles, CA 90095
5Carnegie Mellon University, Department of Physics, Pittsburgh, Pennsylvania 15213
6Catholic University of America, Department of Physics, Washington, D.C. 20064
7CEA Saclay, DAPNIA-SPhN, F91191 Gif-sur-Yvette Cedex, France
8University of Connecticut, Physics Department, Storrs, Connecticut 06269
9University Blaise Pascal/IN2P3, Aubiere Cedex, France
10Duke University, Physics Department, Durham, North Carolina 27706
11Edinburgh University, Department of Physics and Astronomy, Edinburgh EH9 3JZ, United Kingdom
12Florida International University, Department of Physics, Miami, Florida 33199
13Florida State University, Department of Physics, Tallahassee, Florida 32306
14Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, C.P. 13, 00044 Frascati, Italy
15Istituto Nazionale di Fisica Nucleare, Sezione di Genova e Dipartimento di Fisica dell'Universita, 16146 Genova, Italy
16The George Washington University, Department of Physics, Washington, D.C. 20052
17Institute of Theoretical and Experimental Physics, Moscow, 117259, Russia
18James Madison University, Department of Physics, Harrisonburg, Virginia 22807
19Kyungpook National University, Department of Physics, Taegu 702-701, South Korea
20University of Massachusetts, Department of Physics, Amherst, Massachusetts 01003
21MIT-Bates Linear Accelerator, Middleton, Massachusetts 01949
22University of New Hampshire, Department of Physics, Durham, New Hampshire 03824
23Norfolk State University, Norfolk, Virginia 23504
24Ohio University, Department of Physics, Athens, Ohio 45701
25Old Dominion University, Department of Physics, Norfolk, Virginia 23529
26Institut de Physique Nucleaire d'Orsay, IN2P3, BP 1, 91406 Orsay, France
27University of Pittsburgh, Department of Physics, Pittsburgh, Pennsylvania 15260
28Rensselaer Polytechnic Institute, Department of Physics, Troy, New York 12181
29Rice University, T.W. Bonner Nuclear Laboratory, Houston, Texas 77005-1892
30University of Richmond, Department of Physics, Richmond, Virginia 23173
31University of South Carolina, Department of Physics, Columbia, South Carolina 29208
32University of Texas, Department of Physics, El Paso, Texas 79968
33University of Virginia, Department of Physics, Charlottesville, Virginia 22903
34Virginia Polytechnic Institute and State University, Department of Physics, Blacksburg, Virginia 24061
35College of William and Mary, Department of Physics, Williamsburg, Virginia 23185
36Yerevan Physics Institute, 375036 Yerevan, Armenia
Received 17 July 2001; published 10 October 2001
We report the first results of the beam-spin asymmetry measured in the reaction e⃗p→epγ at a beam energy of 4.25 GeV. A large asymmetry with a sinφ modulation is observed, as predicted for the interference term of deeply virtual compton scattering (DVCS) and the Bethe-Heitler process. The amplitude of this modulation is α = 0.202±0.028. In leading-order and leading-twist perturbative QCD, the α is directly proportional to the imaginary part of the DVCS amplitude.
© 2001 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.87.182002
DOI:
10.1103/PhysRevLett.87.182002
PACS:
13.60.Fz, 14.20.Dh, 24.85.+p
*Present address: Systems Planning and Analysis, 2000 North Beauregard Street, Suite 400, Alexandria, Virginia 22311. †Present address: Department of Physics, University of New Hampshire, Durham, New Hampshire 03824. ‡Present address: Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606. §Present address: Department of Physics, Catholic University of America, Washington, D.C. 20064. **Present address: The Motley Fool, Alexandria, Virginia 22314.
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