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

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