Phys. Rev. Lett.
95,
102001
(2005)
[6 pages]
Recoil Polarization for Δ Excitation in Pion Electroproduction
J. J. Kelly et al. Jefferson Laboratory E91011 and Hall A Collaborations
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J. J. Kelly1, R. E. Roché2, Z. Chai3, M. K. Jones4, O. Gayou3, A. J. Sarty5, S. Frullani6, K. Aniol7, E. J. Beise1, F. Benmokhtar8, W. Bertozzi3, W. U. Boeglin9, T. Botto10, E. J. Brash11, H. Breuer1, E. Brown12, E. Burtin13, J. R. Calarco14, C. Cavata13, C. C. Chang1, N. S. Chant1, J.-P. Chen4, M. Coman9, D. Crovelli8, R. De Leo6, S. Dieterich8, S. Escoffier13, K. G. Fissum15, V. Garde16, F. Garibaldi6, S. Georgakopoulus10, S. Gilad3, R. Gilman8, C. Glashausser8, J.-O. Hansen4, D. W. Higinbotham3, A. Hotta17, G. M. Huber11, H. Ibrahim18, M. Iodice6, C. W. de Jager4, X. Jiang8, A. Klimenko18, A. Kozlov11, G. Kumbartzki8, M. Kuss4, L. Lagamba6, G. Laveissière16, J. J. LeRose4, R. A. Lindgren19, N. Liyanage4, G. J. Lolos11, R. W. Lourie20, D. J. Margaziotis7, F. Marie13, P. Markowitz9, S. McAleer2, D. Meekins2, R. Michaels4, B. D. Milbrath21, J. Mitchell4, J. Nappa8, D. Neyret13, C. F. Perdrisat22, M. Potokar23, V. A. Punjabi24, T. Pussieux13, R. D. Ransome8, P. G. Roos1, M. Rvachev3, A. Saha4, S. Širca3, R. Suleiman3, S. Strauch8, J. A. Templon12, L. Todor18, P. E. Ulmer18, G. M. Urciuoli6, L. B. Weinstein18, K. Wijesooriya25, B. Wojtsekhowski4, X. Zheng3, and L. Zhu3 (Jefferson Laboratory E91011 and Hall A Collaborations)
1Department of Physics, University of Maryland, College Park, Maryland 20742, USA
2Florida State University, Tallahassee, Florida 32306, USA
3Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
5Saint Mary’s University, Halifax, Nova Scotia, Canada B3H 3C3
6Istituto Nazionale di Fisica Nucleare, Sezione Sanità and Istituto Superiore di Sanità, Physics Laboratory, 00161 Roma, Italy
7California State University Los Angeles, Los Angeles, California 90032, USA
8Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
9Florida International University, Miami, Florida 33199, USA
10University of Athens, Athens, Greece
11University of Regina, Regina, Saskatchewan, Canada S4S 0A2
12University of Georgia, Athens, Georgia 30602, USA
13CEA Saclay, F-91191 Gif-sur-Yvette, France
14University of New Hampshire, Durham, New Hampshire 03824, USA
15University of Lund, Box 118, SE-221 00 Lund, Sweden
16Université Blaise Pascal Clermont Ferrand et CNRS/IN2P3 LPC 63, 177 Aubière Cedex, France
17University of Massachusetts, Amherst, Massachusetts 01003, USA
18Old Dominion University, Norfolk, Virginia 23529, USA
19University of Virginia, Charlottesville, Virginia 22901, USA
20Renaissance Technologies Corporation, Setauket, New York 11733, USA
21Eastern Kentucky University, Richmond, Kentucky 40475, USA
22College of William and Mary, Williamsburg, Virginia 23187, USA
23Institut Jožef Stefan, University of Ljubljana, SI-1001 Ljubljana, Slovenia
24Norfolk State University, Norfolk, Virginia 23504, USA
25University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
Received 24 May 2005; published 29 August 2005
We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q2=1.0 (GeV/c)2, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S1+/M1+)=-(6.84±0.15)% and Re (E1+/M1+)=-(2.91±0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ℓπ≤1 truncation.
© 2005 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.95.102001
DOI:
10.1103/PhysRevLett.95.102001
PACS:
14.20.Gk, 13.60.Le, 13.40.Gp, 13.88.+e
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