Measurements of the generalized electric and magnetic polarizabilities of the proton at low<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math>using the virtual Compton scattering reaction

Abstract

Experimental details of a virtual Compton scattering (VCS) experiment performed on the proton at the MIT-Bates out-of-plane scattering facility are presented. The VCS response functions ${P}_{LL}\ensuremath{-}{P}_{TT}/\phantom{{P}_{TT}\ensuremath{\varepsilon}}\ensuremath{\varepsilon}$ and ${P}_{LT}$ have been measured at ${Q}^{2}=0.057\phantom{\rule{0.28em}{0ex}}{\mathrm{GeV}}^{2}/{c}^{2}$. The generalized electric and magnetic polarizabilities, $\ensuremath{\alpha}({Q}^{2})$ and $\ensuremath{\beta}({Q}^{2})$, and the mean-square electric polarizability radius$\ensuremath{\langle}{r}_{\ensuremath{\alpha}}^{2}\ensuremath{\rangle}$ are obtained from a dispersion analysis of the data. The results are in good agreement with $O({p}^{3})$ heavy baryon chiral perturbation and indicate the dominance of mesonic effects in the polarizabilities.