Precision Measurement of the P(e, Ép) ?0 Reaction at Threshold

Download or read book Precision Measurement of the P(e, Ép) ?0 Reaction at Threshold written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: New results are reported from a measurement of $\pi0̂$ electroproduction near threshold using the p(e, ép) ?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 $\phi*̂_{\pi}$ and $\theta*̂_{\pi}$ angles in the $p \pi0̂$ center-of-mass was obtained for invariant energies above threshold from 0.5 MeV up to 15 MeV. The 4-momentum transfer $Q2̂$ coverage ranges from 0.05 to 0.155 (GeV/c)$2̂$ in fine steps. A simple phenomenological analysis of our data shows strong disagreement with $p-$wave predictions from ChPT for $Q2̂>0.07$ (GeV/c)$2̂$, while the $s-$wave predictions are in reasonable agreement.