On approaches to measure the electromagnetic polarizabilities of the neutron

F. Wissmann; M.I. Levchuk; M. Schumacher

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Hadrons and Nuclei

Eur. Phys. J. A 1, 193-200

On approaches to measure the electromagnetic polarizabilities of the neutron

F. Wissmann¹ - M.I. Levchuk² - M. Schumacher¹

¹ II. Physikalisches Institut, Universität Göttingen, Bunsenstrasse 7-9, D-37073 Göttingen, Germany
² B.I. Stepanov Institute of Physics, Belarusian Academy of Sciences, F. Skaryna prospect 70, 220072, Minsk, Belarus

Received: 25 August 1997 / Revised version: 5 November 1997 Communicated by B. Povh

Abstract
The present experimental state of the neutron polarizabilities is discussed. Two possibilities to extract the neutron polarizabilities from experiments are considered: i) quasi-free Compton scattering from the bound neutron and ii) scattering of slow neutrons in the Coulomb field of heavy nuclei. The latter experiments have led to an intense discussion from which we conclude that all attempts to measure the neutron polarizabilities using this method have failed. It is shown that quasi-free Compton scattering from the neutron bound in the deuteron at photon energies from 200 MeV to 300 MeV is the most promising method of measuring the neutron polarizabilities. To arrive at an experimental accuracy of $\pm 2\cdot 10^{-4}\mbox{fm}^{3}$ when extracting the electric polarizability ${\bar \alpha}_n$ , one has to measure the differential cross section in the energy range from 200 MeV to 300 MeV at backward photon scattering angles with a precision of 5%. It is shown that theoretical uncertainties of the method are mainly due to the dependence of the cross section on the selection of multipole analysis of single pion photoproduction. At present they prevent the extraction of ${\bar \alpha}_n$ with an accuracy better than $\pm 2\cdot 10^{-4}\mbox{fm}^{3}$ .