Phys. Rev. Lett.
97,
112003
(2006)
[6 pages]
Measurement of the N→Δ+(1232) Transition at High-Momentum Transfer by π0 Electroproduction
M. Ungaro et al. CLAS Collaboration
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M. Ungaro1,2,3, P. Stoler1, I. Aznauryan3,40, V. D. Burkert3, K. Joo2, L. C. Smith38, G. Adams1, M. Amarian31, P. Ambrozewicz13, M. Anghinolfi19, G. Asryan40, G. Audit9, H. Avakian3, H. Bagdasaryan40,31, J. P. Ball4, N. A. Baltzell35, S. Barrow14, V. Batourine24, M. Battaglieri19, I. Bedliski22, M. Bektasoglu31,30, M. Bellis1,7, N. Benmouna15, B. L. Berman15, A. S. Biselli1,7, B. E. Bonner33, S. Bouchigny20, S. Boiarinov22,3, R. Bradford7, D. Branford11, W. J. Briscoe15, W. K. Brooks3, S. Bültmann31, C. Butuceanu39, J. R. Calarco28, S. L. Careccia31, D. S. Carman30, A. Cazes35, S. Chen14, P. L. Cole3,8,17, P. Coltharp14, D. Cords3, P. Corvisiero19, D. Crabb38, J. P. Cummings1, E. De Sanctis18, R. DeVita19, P. V. Degtyarenko3, H. Denizli32, L. Dennis14, A. Deur3, K. V. Dharmawardane31, C. Djalali35, G. E. Dodge31, J. Donnelly16, D. Doughty10,3, M. Dugger4, S. Dytman32, O. P. Dzyubak35, H. Egiyan39,3, K. S. Egiyan40, L. Elouadrhiri3, P. Eugenio14, R. Fatemi38, G. Fedotov27, G. Feldman15, R. J. Feuerbach7, H. Funsten39, M. Garçon9, G. Gavalian28,31, G. P. Gilfoyle34, K. L. Giovanetti23, F. X. Girod9, J. Goetz5, C. I. O. Gordon16, R. W. Gothe35, K. A. Griffioen39, M. Guidal20, M. Guillo35, N. Guler31, L. Guo3, V. Gyurjyan3, C. Hadjidakis20, R. S. Hakobyan8, J. Hardie10,3, D. Heddle3, F. W. Hersman28, I. Hleiqawi30, M. Holtrop28, K. Hicks30, C. E. Hyde-Wright31, Y. Ilieva15, D. G. Ireland16, B. S. Ishkhanov27, M. M. Ito3, D. Jenkins37, H. S. Jo20, H. G. Juengst15,31, J. D. Kellie16, M. Khandaker29, W. Kim24, A. Klein31, F. J. Klein8, A. V. Klimenko31, M. Kossov22, L. H. Kramer13,3, V. Kubarovsky1, J. Kuhn1,7, S. E. Kuhn31, J. Lachniet7,31, J. M. Laget3, J. Langheinrich35, D. Lawrence26, T. Lee28, Ji Li1, K. Livingston16, C. Marchand9, N. Markov2, S. McAleer14, B. McKinnon16, J. W. C. McNabb7, B. A. Mecking3, S. Mehrabyan32, J. J. Melone16, M. D. Mestayer3, C. A. Meyer7, K. Mikhailov22, R. Minehart38, M. Mirazita18, R. Miskimen26, V. Mokeev27, L. Morand9, S. A. Morrow20,9, J. Mueller32, G. S. Mutchler33, J. Napolitano1, R. Nasseripour13, S. Niccolai15,20, G. Niculescu30,23, I. Niculescu15,3,23, B. B. Niczyporuk3, M. Niroula31, R. A. Niyazov31,3, M. Nozar3, G. V. O’Rielly15, M. Osipenko19,27, A. I. Ostrovidov14, K. Park24, E. Pasyuk4, S. A. Philips15, N. Pivnyuk22, D. Pocanic38, O. Pogorelko22, E. Polli18, S. Pozdniakov22, B. M. Preedom35, J. W. Price6, Y. Prok38,3,*, D. Protopopescu28,16, L. M. Qin31, B. A. Raue13,3, G. Riccardi14, G. Ricco19, M. Ripani19, B. G. Ritchie4, F. Ronchetti18, G. Rosner16, P. Rossi18, P. D. Rubin34, F. Sabatié9, C. Salgado29, J. P. Santoro37,3,8, V. Sapunenko3, R. A. Schumacher7, V. S. Serov22, Y. G. Sharabian3, A. V. Skabelin25, E. S. Smith3, D. I. Sober8, A. Stavinsky22, S. S. Stepanyan24, S. Stepanyan10,3, B. E. Stokes14, I. I. Strakovsky15, S. Strauch15,35, M. Taiuti19, D. J. Tedeschi35, U. Thoma3,21,12,†, A. Tkabladze30,15, L. Todor7,34, S. Tkachenko31, C. Tur35, M. F. Vineyard36,34, A. V. Vlassov22, L. B. Weinstein31, D. P. Weygand3, M. Williams7, E. Wolin3, M. H. Wood35,‡, A. Yegneswaran3, L. Zana28, B. Zhang25, J. Zhang31, and B. Zhao2 (CLAS Collaboration)
1Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA
2University of Connecticut, Storrs, Connecticut 06269, USA
3Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, 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, DC 20064, USA
9CEA-Saclay, Service de Physique Nucléaire, F91191 Gif-sur-Yvette, Cedex, France
10Christopher Newport University, Newport News, Virginia 23606, USA
11Edinburgh University, Edinburgh EH9 3JZ, United Kingdom
12Emmy-Noether Foundation, Germany
13Florida International University, Miami, Florida 33199, USA
14Florida State University, Tallahassee, Florida 32306, USA
15The George Washington University, Washington, DC 20052, USA
16University of Glasgow, Glasgow G12 8QQ, United Kingdom
17Idaho State University, Pocatello, Idaho 83209, USA
18INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
19INFN, Sezione di Genova, 16146 Genova, Italy
20Institut de Physique Nucleaire ORSAY, Orsay, France
21Institute für Strahlen und Kernphysik, Universität Bonn, Germany
22Institute of Theoretical and Experimental Physics, Moscow, 117259, Russia
23James Madison University, Harrisonburg, Virginia 22807, USA
24Kyungpook National University, Daegu 702-701, South Korea
25Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
26University of Massachusetts, Amherst, Massachusetts 01003, USA
27Moscow State University, General Nuclear Physics Institute, 119899 Moscow, Russia
28University of New Hampshire, Durham, New Hampshire 03824-3568, USA
29Norfolk State University, Norfolk, Virginia 23504, USA
30Ohio University, Athens, Ohio 45701, USA
31Old Dominion University, Norfolk, Virginia 23529, USA
32University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
33Rice University, Houston, Texas 77005-1892, USA
34University of Richmond, Richmond, Virginia 23173, USA
35University of South Carolina, Columbia, South Carolina 29208, 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 16 June 2006; published 15 September 2006
We report a new measurement of the exclusive electroproduction reaction γ*p→π0p to explore the evolution from soft nonperturbative physics to hard processes via the Q2 dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the N→Δ transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c2, 4π center-of-mass solid angle, and Q2 from 3 to 6 GeV2/c2, the highest yet achieved. It is found that the magnetic form factor GM* decreases with Q2 more steeply than the proton magnetic form factor, the ratio E1+/M1+ is small and negative, indicating strong helicity nonconservation, and the ratio S1+/M1+ is negative, while its magnitude increases with Q2.
© 2006 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.97.112003
DOI:
10.1103/PhysRevLett.97.112003
PACS:
13.60.Le, 13.40.Gp, 14.20.Gk
*Current address: Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA. †Current address: Physikalisches Institut der Universitaet Giessen, 35392 Giessen, Germany. ‡Current address: University of Massachusetts, Amherst, MA 01003, USA.
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