The Higgs boson decays with the lepton flavor violation

Abstract

Within the left-right symmetric model (LRM) the decays $$S_1\to {\mu }^{+}+{\tau }^{-},S_1\to {\mu }^{-}+{\tau }^{+}$$ where $S_1$ is an analog of the standard model Higgs boson, are considered. The widths of this decays are found in the third order of the perturbation theory. Since the main contribution to the decay widths is caused by the diagram with the light and heavy neutrinos in the virtual state then investigation of this decays could shed light upon the neutrino sector structure. The obtained decay widths critically depend on the charged gauge bosons mixing angle $\xi$ and the heavy-light neutrinos mixing angle $\phi$. The LRM predicts the values of these angles as functions of the vacuum expectation values $v_L$ and $v_R$. Using the results of the existing experiments, on looking for the additional charged gauge boson $W_2$ and on measuring the electroweak $\rho$ parameter, gives $$\sin \xi \le 5\times 10^{-4},\sin \phi \le 2.3\times 10^{-2}.$$ However, even using the upper bounds on $\sin \xi$ and $\sin \phi$ one does not manage to get the upper experimental bound on the branching ratio $\text{mbox}BR(S_1\to \tau \mu {)}_{exp}$ being equal to $0.25\times 10^{-2}$. The theoretical expression proves to be on two orders of magnitude less than $\text{mbox}BR(S_1\to \tau \mu {)}_{exp}$.

Comments: 18 pages, 1 figure