On neutrino masses in the MSSM with BRpV

One-loop corrections to the neutrino mass matrix within the MSSM with bilinear R-parity violation are calculated, paying attention to the approach in which an effective neutrino mass matrix is used. The full mass matrix is block-diagonalized, it is found that second and third order terms can be numerically important, and this is analytically understood. Top–stop loops do not contribute to th effective approach at the first order, nevertheless they contribute at the third. An improved approach that includes these effects is proposed. A scan over parameter space is made supporting the conclusions.