Phys. Rev. Lett.
84,
1398–1402
(2000)
GEp/GMp Ratio by Polarization Transfer in e⃗p → ep⃗
M. K. Jones et al. (The Jefferson Lab Hall A Collaboration)
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M. K. Jones1, K. A. Aniol7, F. T. Baker4, J. Berthot6, P. Y. Bertin6, W. Bertozzi22, A. Besson6, L. Bimbot26, W. U. Boeglin10, E. J. Brash5, D. Brown21, J. R. Calarco23, L. S. Cardman30, C.-C. Chang21, J.-P. Chen30, E. Chudakov30, S. Churchwell8, E. Cisbani15, D. S. Dale18, R. De Leo14, A. Deur6,30, B. Diederich25, J. J. Domingo30, M. B. Epstein7, L. A. Ewell21, K. G. Fissum22, A. Fleck5, H. Fonvieille6, S. Frullani15, J. Gao22, F. Garibaldi15, A. Gasparian13,18, G. Gerstner1, S. Gilad22, R. Gilman2,30, A. Glamazdin19, C. Glashausser2, J. Gomez30, V. Gorbenko19, A. Green33, J.-O. Hansen30, C. R. Howell8, G. M. Huber5, M. Iodice15, C. W. de Jager30, S. Jaminion6, X. Jiang2, W. Kahl28, J. J. Kelly21, M. Khayat17, L. H. Kramer10, G. Kumbartzki2, M. Kuss30, E. Lakuriki29, G. Lavessière6, J. J. LeRose30, M. Liang30, R. A. Lindgren32, N. Liyanage22, G. J. Lolos5, R. Macri8, R. Madey17, S. Malov2, D. J. Margaziotis7, P. Markowitz10, K. McCormick25, J. I. McIntyre2, R. L. J. van der Meer5, R. Michaels30, B. D. Milbrath9, J. Y. Mougey12, S. K. Nanda30, E. A. J. M. Offermann30, Z. Papandreou5, C. F. Perdrisat1, G. G. Petratos17, N. M. Piskunov16, R. I. Pomatsalyuk19, D. L. Prout17, V. Punjabi3, G. Quéméner1,12, R. D. Ransome2, B. A. Raue10, Y. Roblin6, R. Roche11, G. Rutledge1, P. M. Rutt30, A. Saha30, T. Saito31, A. J. Sarty11, T. P. Smith23, P. Sorokin19, S. Strauch2, R. Suleiman17, K. Takahashi31, J. A. Templon4, L. Todor25, P. E. Ulmer25, G. M. Urciuoli15, P. Vernin27, B. Vlahovic24, H. Voskanyan34, K. Wijesooriya1, B. B. Wojtsekhowski30, R. J. Woo20, F. Xiong22, G. D. Zainea5, and Z.-L. Zhou22 (The Jefferson Lab Hall A Collaboration)
1College of William and Mary, Williamsburg, Virginia 23187
2Rutgers, The State University of New Jersey, Piscataway, New Jersey 08855
3Norfolk State University, Norfolk, Virginia 23504
4University of Georgia, Athens, Georgia 30602
5University of Regina, Regina, SK S4S OA2, Canada
6Université Blaise Pascal/CNRS-IN2P3, F-63177 Aubière, France
7California State University at Los Angeles, Los Angeles, California 90032
8Duke University and TUNL, Durham, North Carolina 27708
9Eastern Kentucky University, Richmond, Kentucky 40475
10Florida International University, Miami, Florida 33199
11Florida State University, Tallahassee, Florida 32306
12Institut des Sciences Nucléaires, CNRS-IN2P3, F-38026 Grenoble, France
13Hampton University, Hampton, Virginia 23668
14INFN, Sezione di Bari and University of Bari, 70126 Bari, Italy
15INFN, Sezione Sanità and Istituto Superiore di Sanità, 00161 Rome, Italy
16JINR-LHE, 141980 Dubna, Moscow Region, Russian Federation
17Kent State University, Kent, Ohio 44242
18University of Kentucky, Lexington, Kentucky 40506
19Kharkov Institute of Physics and Technology, Kharkov, 310108, Ukraine
20University of Manitoba, Winnipeg, MB R3T 2N2, Canada
21University of Maryland, College Park, Maryland 20742
22Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
23University of New Hampshire, Durham, New Hampshire 03824
24North Carolina Central University, Durham, North Carolina 27707
25Old Dominion University, Norfolk, Virginia 23508
26Institut de Physique Nucléaire, F-91406 Orsay, France
27CEA Saclay, F-91191 Gif-sur-Yvette, France
28Syracuse University, Syracuse, New York 13244
29Temple University, Philadelphia, Pennsylvania 19122
30Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606
31Tohoku University, Sendai 980, Japan
32University of Virginia, Charlottesville, Virginia 22901
33Western Cape University, Capetown, South Africa
34Yerevan Physics Institute, Yerevan 375036, Armenia
Received 4 October 1999; published in the issue dated 14 February 2000
The ratio of the proton's elastic electromagnetic form factors, GEp/GMp, was obtained by measuring Pt and Pℓ, the transverse and the longitudinal recoil proton polarization, respectively. For elastic e⃗p→ep⃗, GEp/GMp is proportional to Pt/Pℓ. Simultaneous measurement of Pt and Pℓ in a polarimeter provides good control of the systematic uncertainty. The results for the ratio GEp/GMp show a systematic decrease as Q2 increases from 0.5 to 3.5GeV2, indicating for the first time a definite difference in the spatial distribution of charge and magnetization currents in the proton.
© 2000 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.84.1398
DOI:
10.1103/PhysRevLett.84.1398
PACS:
25.30.Bf, 13.40.Gp, 14.20.Dh, 24.70.+s
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