Four-Leptonic Decays of Charged and Neutral B Mesons within the Standard Model

The branching ratios and differential distributions for the four-leptonic decays , , and are calculated within the Standard Model. The branching ratios for the rare decays B (d,s) -> e (+) e (-) mu (+) mu (-) and B (d,s) -> mu (+) mu (-) mu (+) mu (-) are estimated. Methods for testing the lepton universality in rare multileptonic decays of charged and neutral B mesons are proposed.