Recent values of the proton charge radius derived from the Lamb shift in electronic hydrogen tend to be larger than those from electron scattering. Therefore low-momentum-transfer scattering data from different groups and laboratories have been reanalyzed with Coulomb and recoil corrections included. This was done by calculating at each scattering angle and scattering energy the corresponding correction obtained from a partial wave program which includes recoil approximately. Corrections due to magnetic scattering were also made before the rms-radius was determined by a fit which allows free normalization for each experiment. It is shown that an analysis of electron scattering data including Coulomb corrections lowers the χ 2 of the fit and increases the proton radius by about (0.008 − 0.013) fm depending on the fit strategy. A value of r p = 0.880 (15) fm is obtained which is in good agreement with the one extracted from Lamb shift measurements. *

No abstract

We apply nonperturbative variational techniques to a relativistic scalar field theory in which heavy bosons ("nucleons") interact with light scalar mesons via a Yukawa coupling. Integrating out the meson field and neglecting the nucleon vacuum polarization one obtains an effective action in terms of the heavy particle coordinates which is nonlocal in the proper time. As in Feynman's polaron approach we approximate this action by a retarded quadratic action whose parameters are to be determined variationally on the pole of the two-point function. Several ansätze for the retardation function are studied and for the most general case we derive a system of coupled variational equations. An approximate analytic solution displays the instability of the system for coupling constants beyond a critical value.

No abstract

We calculate the second-order corrections to the atomic S-level shifts in electronic and muonic deuterium due to virtual excitations of the deuteron using wave functions from realistic potentials.Common approximations like the long-wavelength limit or the closure approximation are avoided by integrating over the inelastic structure functions of the deuteron with specified weight functions. Transverse excitations are also included consistently. We estimate the potential dependence of our numerical results to be less than 2'Fo.PACS number(s): 12.20. Ds, 25.30.c, 36.10.Dr, 21.10.Ft