Surface Vibrations of the Nucleon

Recently a “dynamical bag model” has been developed such that the nucleon consists of a vibrating bag with quarks confined in it. The bag radius is a dynamical variable, and the Roper resonance is identified as an excitation of the breathing mode. In this paper we show that the same model well reproduces the empirical charge distribution of the proton. This is in contrast to the MIT bag model in its static cavity approximation which leads to an unnatural distribution with a sharp edge at the bag surface. Effects of nonadiabatic corrections to the bag-quark coupling are also examined.