Search

We explore the neutrino signals from proton decays catalyzed by GUT monopoles in the Sun. Three typical proton decay modes, $p rightarrow e^+ + (rho^0, eta, omega...) rightarrow pi^+$, $p rightarrow mu^+ K^0$ and $p rightarrow bar{nu}_e pi^+$, have been analyzed for the Super-Kamiokande experiment. The monopole-induced neutrinos arise from interactions and subsequent decays of the proton decay products. To obtain the neutrino energy spectra, we use the Geant4 software to simulate propagations of daughter particles in the highly-dense solar center. It is found that $K^0$ can produce a large amount of 236 MeV monoenergetic $nu_mu$ neutrinos through the charge exchange process $K^0 + p rightarrow K^+ + n$ and the subsequent decay $K^+ rightarrow mu^+ nu_mu$ at rest. Based on this interesting feature, $p rightarrow mu^+ K^0$ can give the best discovery potential among three decay modes for most of the parameter space. In addition, we present the Super-Kamiokande sensitivities to the monopole flux for three proton decay modes.

We present an undated comprehensive analysis for the simplest dark matter model in which a real singlet scalar with a $Z_2$ symmetry is introduced to extend the standard model. According to the observed dark matter abundance, we predict the dark matter direct and indirect detection cross sections for the whole parameter space. The Breit-Wigner resonance effect has been considered to calculate the thermally averaged annihilation cross section. It is found that three regions can be excluded by the current direct and indirect dark matter search experiments. In addition, we also discuss the implication of this model for the Higgs searches at colliders., Comment: 14 pages, 7 figures. discussion and references added, published in JHEP

We investigate the lepton flavor violating (LFV) rare decays in the supersymmetric minimal seesaw model in which the Frampton-Glashow-Yanagida ansatz is incorporated. The branching ratio of $\mu \to e \gamma$ is calculated in terms of the Snowmass Points and Slopes (SPS). We find that the inverted mass hierarchy is disfavored by all SPS points. In addition, once the ratio of BR$(\tau \to \mu \gamma)$ to BR$(\mu \to e \gamma)$ is measured, one may distinguish the normal and inverted neutrino mass hierarchies, and confirm the masses of heavy right-handed Majorana neutrinos by means of the LFV processes and the thermal leptogenesis mechanism. It is worthwhile to stress that this conclusion is independent of the supersymmetric parameters., Comment: 12 pages, 5 figures, 1 table. Comments and references added, accepted for publication in Phys. Rev. D

In the framework of type II seesaw mechanism we propose two simple but instructive ansatze for neutrino mixing and leptogenesis. In each ansatz, the effective Majorana neutrino mass matrix is composed of two parts -- the part with Z_2 symmetry arises from the ordinary type I seesaw mechanism and the part with S_3 symmetry arises from an additional Higgs triplet vacuum expectation value. The two ansatze can simultaneously account for the current neutrino oscillation data and the cosmological baryon number asymmetry via leptogenesis., Comment: RevTex 14 pages, 1 table. More discussions and references added. To appear in Phys. Rev. D

We show that all nontrivial CP-violating phases can be determined in terms of three lepton flavor mixing angles and the ratio of $\Delta m^2_{\rm sun}$ to $\Delta m^2_{\rm atm}$ in the minimal seesaw model in which the Frampton-Glashow-Yanagida (FGY) ansatz is incorporated. This important point allows us to make very specific predictions for the cosmological baryon number asymmetry and CP violation in neutrino oscillations. A measurement of the smallest neutrino mixing angle will sensitively test the FGY ansatz, in particular in the case that three light neutrinos have a normal mass hierarchy., Comment: RevTex 13 pages (3 PS figures included). A new figure and references added

We calculate the rephasing invariants of CP and T violation in a favorable parametrization of the 4x4 lepton flavor mixing matrix. Their relations with the CP- and T-violating asymmetries in neutrino oscillations are derived, and the matter effects are briefly discussed., RevTex 9 pages. Slight changes. Phys. Rev. D (in press)