2018 Impact factor 2.481
Hadrons and Nuclei


Eur. Phys. J. A 10, 207-215

Low-energy Compton scattering and the polarizabilities of the proton

V. Olmos de León1, F. Wissmann2, P. Achenbach3, J. Ahrens1, H.-J. Arends1, R. Beck1, P.D. Harty4, V. Hejny3, P. Jennewein1, M. Kotulla3, B. Krusche3, V. Kuhr2, R. Leukel1, J.C. McGeorge4, V. Metag3, R. Novotny3, A. Polonski5, F. Rambo2, A. Schmidt1, M. Schumacher2, U. Siodlaczek6, H. Ströher3, A. Thomas1, J. Weiß3 and M. Wolf3

1  Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany
2  II. Physikalisches Institut, Universität Göttingen, D-37073 Göttingen, Germany
3  II. Physikalisches Institut, Universität Giessen, D-35392 Giessen, Germany
4  Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
5  INR, Russian Academy of Sciences, Moscow, Russia
6  Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany

fwissma@gwdg.de

(Received: 9 January 2001 / Revised version: 8 February 2001 Communicated by M. Garçon)

Abstract
Differential cross-sections for Compton scattering from the proton have been measured at the MAMI tagged photon facility using the TAPS setup. The data cover an angular range of $\theta_{\gamma}^{\rm lab} = 59^\circ {--} 155^\circ$ and photon energies ranging from 55 MeV to 165 MeV. Our results are in good agreement with those from previous experiments, but yield higher precision. Using dispersion relations the proton polarizabilities have been determined to be $\bar{\alpha}= \lbrack11.9 \pm 0.5_{\rm stat.} \mp 1.3_{\rm syst.}
\pm 0.3_{\rm mod.}\rbrack\cdot 10^{-4} {\rm fm}^3$ and $\bar{\beta}= \lbrack1.2 \pm 0.7_{\rm stat.} \pm 0.3_{\rm syst.} \pm
0.4_{\rm mod.})\rbrack\cdot 10^{-4} {\rm fm}^3$. These results confirm the Baldin sum rule which was re-evaluated to be $\bar{\alpha}+ \bar{\beta}= \lbrack 13.8 \pm 0.4\rbrack\cdot 10^{-4} {\rm fm}^3$. We can also conclude that there is no significant additional asymptotic contribution to the backward spin polarizability $\gamma_\pi$ beyond the t-channel $\pi^0$-exchange.

PACS
11.55.Fv - Dispersion relation.
13.60.Fz - Elastic and Compton scattering.
14.20.Dh - Proton and neutrons.
25.20.Dc - Photon absorption and scattering.

© Società Italiana di Fisica, Springer-Verlag 2001