Weak Decays of Doubly Heavy Baryons: Bcc→BcV{\cal B}_{cc}\to {\cal B}_c V

The weak decays of a spin-$1/2$ doubly charm baryon (${\cal B}_{cc}$) to a spin-$1/2$ singly charm baryon (${\cal B}_c$) and a light vector meson ($V$) are studied under a phenomenological scheme. The contributions are classified into different topological diagrams, among which the short distance ones are calculated under the factorization hypothesis, and the long distance contributions are modelled as final-state interactions (FSIs) which are estimated with the one-particle-exchange model. In calculation the topological contributions tend to fall in a hierarchy. The branching fractions or decay widths are estimated, and it indicates that $\Xi_{cc}^+\to\Xi_c^+\pi^+\pi^-$ and $\Omega_{cc}^{+}\rightarrow\Xi_{c}^{+}K^-\pi^+$ can be used as candidate decays for searching $\Xi_{cc}^+$ and $\Omega_{cc}^+$. Some decays that are mainly activated by the long distance effects are found, observation on which in future experiments can help to understand the role of FSIs in charm baryon decays.Comment: 29 pages, 5 figures, 7 tables; version published in EPJ

Higgs Decay h→μτh\to\mu\tau with Minimal Flavor Violation

We consider the tentative indication of flavor-violating Higgs boson decay $h\to\mu\tau$ recently reported in the CMS experiment within the framework of minimal flavor violation. Specifically, we adopt the standard model extended with the seesaw mechanism involving right-handed neutrinos plus effective dimension-six operators satisfying the minimal flavor violation principle in the lepton sector. We find that it is possible to accommodate the CMS $h\to\mu\tau$ signal interpretation provided that the right-handed neutrinos couple to the Higgs boson in some nontrivial way. We take into account empirical constraints from other lepton-flavor-violating processes and discuss how future searches for the $\mu\to e\gamma$ decay and $\mu\to e$ conversion in nuclei may further probe the lepton-flavor-violating Higgs couplings.Comment: 15 pages, no figures, minor errors corrected, references added, matches publicatio

Cosmic e^\pm, \bar p, \gamma and neutrino rays in leptocentric dark matter models

Dark matter annihilation is one of the leading explanations for the recently observed $e^\pm$ excesses in cosmic rays by PAMELA, ATIC, FERMI-LAT and HESS. Any dark matter annihilation model proposed to explain these data must also explain the fact that PAMELA data show excesses only in $e^\pm$ spectrum but not in anti-proton. It is interesting to ask whether the annihilation mode into anti-proton is completely disallowed or only suppressed at low energies. Most models proposed have negligible anti-protons in all energy ranges. We show that the leptocentric $U(1)_{B-3L_i}$ dark matter model can explain the $e^\pm$ excesses with suppressed anti-proton mode at low energies, but at higher energies there are sizable anti-proton excesses. Near future data from PAMELA and AMS can provide crucial test for this type of models. Cosmic $\gamma$ ray data can further rule out some of the models. We also show that this model has interesting cosmic neutrino signatures.Comment: Latex 20 pages and five figures. References adde