A precision measurement of the $p$($e,e^{\prime }p$)${\pi }^0$ reaction at threshold

Abstract

New results are reported from a measurement of ${\pi }^0$ electroproduction near threshold using the $p(e,e^{\prime }p){\pi }^0$ 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 ${\varphi }_{\pi }^{\ast }$ and ${\theta }_{\pi }^{\ast }$ 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.

arXiv comment5 pages, 6 figures

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Cited by in corpus (4)

• Model Selection for Pion Photoproduction
• Exclusive ${\mathbf{\pi }}^0\mathbf{p}$ electroproduction off protons in the resonance region at photon virtualities 0.4~GeV${}^2$ $\le {\mathbf{Q}}^2\le 1$~GeV${}^2$
• Pion photo- and electroproduction and the chiral MAID interface
• Pion Photo- and Electroproduction and the Chiral MAID Interface