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 3×33×3 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 the effective 3×33×3 approach at the first order, nevertheless they contribute at the third. An improved 3×33×3 approach that includes these effects is proposed. A scan over parameter space is made supporting the conclusions.