Exclusive measurements of virtual bremsstrahlung in proton-proton scattering at 190 MeV

Exclusive differential cross sections of virtual bremsstrahlung ih proton-proton scattering below the pion-production threshold have been measured for the first time. The total cross section integrated over photon invariant masses of 15 to 80 MeV/c(2) and integrated over the acceptance of the detector is 3.2 +/- 0.1 +/- 0.5 pb. The data are compared to a low-energy calculation and a fully relativistic microscopic model, which predict a virtual bremsstrahlung cross section of 3.4 and 5.9 pb, respectively. Over the entire experimentally covered phase space, the low-energy calculation gives a better description of the data than the microscopic model. [S0031-9007(99)08793-1].