Well-established nucleon resonances revisited by double-polarization measurements
Abstract
The first measurement is reported of the double-polarization observable G in photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand {\gamma}p -> p{\pi} 0 as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N (1535) with spin-parity J^P = 1/2^- and N (1520) with J^P = 3/2^- . In the third resonance region, where N (1680) with J^P = 5/2^+ production dominates, the new data are reasonably close to the predictions.
Keywords
Cite
@article{arxiv.1207.2686,
title = {Well-established nucleon resonances revisited by double-polarization measurements},
author = {A. Thiel and A. V. Anisovich and D. Bayadilov and B. Bantes and R. Beck and Yu. Beloglazov and M. Bichow and S. Böse and K. -Th. Brinkmann and Th. Challand and V. Crede and F. Dietz and P. Drexler and H. Dutz and H. Eberhardt and D. Elsner and R. Ewald and K. Fornet-Ponse and St. Friedrich and F. Frommberger and Ch. Funke and M. Gottschall and M. Grüner and E. Gutz and Ch. Hammann and J. Hannappel and J. Hartmann and W. Hillert and Ph. Hoffmeister and Ch. Honisch and I. Jaegle and I. Jürgensen and D. Kaiser and H. Kalinowsky and F. Kalischewski and S. Kammer and I. Keshelashvili and V. Kleber and F. Klein and E. Klempt and B. Krusche and M. Lang and I. Lopatin and Y. Maghrbi and K. Makonyi and V. Metag and W. Meyer and J. Müller and M. Nanova and V. Nikonov and R. Novotny and D. Piontek and G. Reicherz and A. Sarantsev and Ch. Schmidt and H. Schmieden and T. Seifen and V. Sokhoyan and V. Sumachev and U. Thoma and H. van Pee and D. Walther and Ch. Wendel and U. Wiedner and A. Wilson and A. Winnebeck and Y. Wunderlich},
journal= {arXiv preprint arXiv:1207.2686},
year = {2015}
}
Comments
Submitted for publication in PRL