Precision Measurement of the $p(e,e^{\text{'}}p){\pi }^0$ Reaction at Threshold

Journal Article · Wed May 13 00:00:00 EDT 2015 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.114.192503 · OSTI ID:1179440

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

New results are reported from a measurement of $$\pi^0$$ 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 $$\phi^*_{\pi}$$ and $$\theta^*_{\pi}$$ angles in the $$p \pi^0$$ center-of-mass was obtained for invariant energies above threshold from 0.5 MeV up to 15 MeV. The 4-momentum transfer $Q^2$ 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 $Q^2>0.07$ (GeV/c)$^2$, while the $s-$wave predictions are in reasonable agreement.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• Contributing Organization: Jefferson Hall A Collaboration
• Grant/Contract Number: FG02-97ER41025; AC05-06OR23177
• OSTI ID: 1179440
• Report Number(s): JLAB/PHY--15-2013; DOE/OR--23177-3313; FG02-97ER41025; NSF MRI Award No. 021635; JLAB-E04-007
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 19 Vol. 114; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English