Precision measurement of the p (e,e'p)π0 reaction at threshold

K. Chirapatpimol, M. H. Shabestari, R. A. Lindgren, L. C. Smith, J. R.M. Annand, D. W. Higinbotham, B. Moffit, V. Nelyubin, B. E. Norum, K. Allada, K. Aniol, K. Ardashev, D. S. Armstrong, R. A. Arndt, F. Benmokhtar, A. M. Bernstein, W. Bertozzi, W. J. Briscoe, L. Bimbot, A. CamsonneJ. P. Chen, S. Choi, E. Chudakov, E. Cisbani, F. Cusanno, M. M. Dalton, C. Dutta, K. Egiyan, C. Fernàndez-Ramìrez, R. Feuerbach, K. G. Fissum, S. Frullani, F. Garibaldi, O. Gayou, R. Gilman, S. Gilad, J. Goity, J. Gomez, B. Hahn, D. Hamilton, J. O. Hansen, J. Huang, R. Igarashi, D. Ireland, C. W. De Jager, X. Jin, X. Jiang, T. Jinasundera, J. Kellie, C. E. Keppel, N. Kolb, J. Lerose, N. Liyanage, K. Livingston, D. McNulty, L. Mercado, R. Michaels, M. Mihovilovič, S. Qian, X. Qian, S. Mailyan, V. Mamyan, S. Marrone, P. Monaghan, S. Nanda, C. F. Perdrisat, E. Piasetzky, D. Protopopescu, V. Punjabi, Y. Qiang, I. A. Rachek, A. Rakhman, S. Riordan, G. Ron, G. Rosner, A. Saha, B. Sawatzky, A. Shahinyan, S. Širca, N. Sparveris, R. R. Subedi, R. Suleiman, I. Strakovsky, V. Sulkosky, J. Moinelo, H. Voskanyan, K. Wang, Y. Wang, J. Watson, D. Watts, B. Wojtsekhowski, R. L. Workman, H. Yao, X. Zhan, Y. Zhang

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Abstract

New results are reported from a measurement of π0 electroproduction near threshold using the p(e,e'p)π0 reaction. The experiment was designed to determine precisely the energy dependence of s- and p-wave electromagnetic multipoles as a stringent test of the predictions of chiral perturbation theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the φπ∗ and θπ∗ angles in the pπ0 center of mass was obtained for invariant energies above threshold from 0.5 up to 15 MeV. The 4-momentum transfer Q2 coverage ranges from 0.05 to 0.155(GeV/c)2 in fine steps. A simple phenomenological analysis of our data shows strong disagreement with p-wave predictions from ChPT for Q2>0.07(GeV/c)2, while the s-wave predictions are in reasonable agreement.

Original languageAmerican English
Article number192503
JournalPhysical Review Letters
Volume114
Issue number19
DOIs
StatePublished - 13 May 2015

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© 2015 American Physical Society.

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