Softly Broken A_4 Symmetry for Nearly Degenerate Neutrino Masses

The leptonic Higgs doublet model of neutrino masses is implemented with an A_4 discrete symmetry (the even permutation of 4 objects or equivalently the symmetry of the tetrahedron) which has 4 irreducible representations: 1, 1', 1'', and 3. The resulting spontaneous and soft breaking of A_4 provides a realistic model of charged-lepton masses as well as a nearly degenerate neutrino mass matrix. Phenomenological consequences at and below the TeV scale are discussed.Comment: 11 pages, no figur

Optical Alignment System for the PHENIX Muon Tracking Chambers

A micron-precision optical alignment system (OASys) for the PHENIX muon tracking chambers is developed. To ensure the required mass resolution of vector meson detection, the relative alignment between three tracking station chambers must be monitored with a precision of 25$\mu$m. The OASys is a straightness monitoring system comprised of a light source, lens and CCD camera, used for determining the initial placement as well as for monitoring the time dependent movement of the chambers on a micron scale.Comment: Accepted for the publication in Nucl.Instr.Meth.

The \tau -> \mu \bar{\nu_i} \nu_i decay in the Randall Sundrum background with localized U(1)_Y gauge boson

We study the effects of localization of the U(1)_Y gauge boson around the visible brane and the contributions of the KK modes of Z bosons on the BR of the LFV \tau -> \mu \bar{\nu_i} \nu_i decay. We observe that the BR is sensitive to the amount of localization of Z boson in the bulk of the Randall Sundrum background.Comment: 13 pages, 4 figures,1 tabl

New "Square Root" Model of Lepton Family Cyclic Symmetry

Following the newly formulated notion of form invariance of the neutrino mass matrix, a complete model of leptons is constructed. It is based on a specific unitary 3 X 3 matrix U in family space, such that U^2 is the simple discrete symmetry nu_e to -nu_e, nu_mu to nu_tau. Thus U also generates the cyclic group Z_4. The charged-lepton mass matrix is nearly diagonal while the neutrino mass matrix is of the form suitable for explaining maximal (large) mixing in atmospheric (solar) neutrino oscillations in the context of three nearly degenerate neutrino masses. Observable lepton flavor violation is predicted. Quarks may be treated in the same way as the charged leptons.Comment: 10 pages, no figur

Supersymmetric Model of Muon Anomalous Magnetic Moment and Neutrino Masses

We propose the novel lepton-number relationship $L_\tau = L_e + L_\mu$, which is uniquely realized by the interaction $(\hat \nu_e \hat \mu - \hat e \hat \nu_\mu) \hat \tau^c$ in supersymmetry and may account for a possibly large muon anomalous magnetic moment. Neutrino masses (with bimaximal mixing) may be generated from the spontaneous and soft breaking of this lepton symmetry.Comment: 10 pages, including 2 figure

Nearly Bi-Maximal Neutrino Mixing, Muon g-2 Anomaly and Lepton-Flavor-Violating Processes

We interpret the newly observed muon g-2 anomaly in the framework of a leptonic Higgs doublet model with nearly degenerate neutrino masses and nearly bi-maximal neutrino mixing. Useful constraints are obtained on the rates of lepton-flavor-violating rare decays $\tau \to \mu \gamma$, $\mu \to e \gamma$ and $\tau \to e \gamma$ as well as the $\mu$-$e$ conversion ratio $R_{\mu e}$. We find that $\Gamma (\mu \to e \gamma)$, $\Gamma (\tau \to e \gamma)$ and $R_{\mu e}$ depend crucially on possible non-zero but samll values of the neutrino mixing matrix element $V_{e3}$, and they are also sensitive to the Dirac-type CP-violating phase. In particular, we show that $\Gamma (\tau \to \mu \gamma)/m^5_\tau$, $\Gamma (\mu \to e \gamma)/m^5_\mu$ and $\Gamma (\tau \to e \gamma)/m^5_\tau$ are approximately in the ratio $1: 2|V_{e3}|^2: 2|V_{e3}|^2$ if $|V_{e3}|$ is much larger than ${\cal O}(10^{-2})$, and in the ratio $2 (\Delta m^2_{\rm atm})^2: (\Delta m^2_{\rm sun})^2:(\Delta m^2_{\rm sun})^2$ if $|V_{e3}|$ is much lower than ${\cal O}(10^{-3})$, where $\Delta m^2_{\rm atm}$ and $\Delta m^2_{\rm sun}$ are the corresponding mass-squared differences of atmospheric and solar neutrino oscillations.Comment: LaTex 6 pages (2 PS figures). Phys. Rev. D (in printing

Lepton flavor violating signals of a little Higgs model at the high energy linear e+e−e^{+}e^{-} colliders

Littlest Higgs $(LH)$ model predicts the existence of the doubly charged scalars $\Phi^{\pm\pm}$, which generally have large flavor changing couplings to leptons. We calculate the contributions of $\Phi^{\pm\pm}$ to the lepton flavor violating $(LFV)$ processes $l_{i}\to l_{j}\gamma$ and $l_{i}\to l_{j}l_{k}l_{k}$, and compare our numerical results with the current experimental upper limits on these processes. We find that some of these processes can give severe constraints on the coupling constant $Y_{ij}$ and the mass parameter $M_{\Phi}$. Taking into account the constraints on these free parameters, we further discuss the possible lepton flavor violating signals of $\Phi^{\pm\pm}$ at the high energy linear $e^{+}e^{-}$ collider $(ILC)$ experiments. Our numerical results show that the possible signals of $\Phi^{\pm\pm}$ might be detected via the subprocesses $e^{\pm}e^{\pm}\to l^{\pm}l^{\pm}$ in the future $ILC$ experiments.Comment: 16 pages, 7 figures. Discussions and references added, typos correcte

TeV-scale seesaw from a multi-Higgs model

We suggest new simple model of generating tiny neutrino masses through a TeV-scale seesaw mechanism without requiring tiny Yukawa couplings. This model is a simple extension of the standard model by introducing extra one Higgs singlet, and one Higgs doublet with a tiny vacuum expectation value. Experimental constraints, electroweak precision data and no large flavor changing neutral currents, are satisfied since the extra doublet only has a Yukawa interaction with lepton doublets and right-handed neutrinos, and their masses are heavy of order a TeV-scale. Since active light neutrinos are Majorana particles, this model predicts a neutrinoless double beta decay.Comment: 21 pages, 8 figure

Slepton Oscillation at Large Hadron Collider

Measurement of Lepton-Flavor Violation (LFV) in the minimal SUSY Standard Model (MSSM) at Large Hadron Collider (LHC) is studied based on a realistic simulation. We consider the LFV decay of the second-lightest neutralino, $\tilde{\chi}^0_2 \to \tilde{l} l' \to l l' \tilde{\chi}^0_1$, in the case where the flavor mixing exists in the right-handed sleptons. We scan the parameter space of the minimal supergravity model (MSUGRA) and a more generic model in which we take the Higgsino mass $\mu$ as a free parameter. We find that the possibility of observing LFV at LHC is higher if $\mu$ is smaller than the MSUGRA prediction; the LFV search at LHC can cover the parameter range where the $\mu \to e \gamma$ decay can be suppressed by the cancellation among the diagrams for this case.Comment: 29 pages, 10 figure

Flavon exchange effects in models with abelian flavor symmetry

In models with abelian flavor symmetry the small mixing angles and mass ratios of quarks and leptons are typically given by powers of small parameters characterizing the spontaneous breaking of flavor symmetry by "flavon" fields. If the scale of the breaking of flavor symmetry is near the weak scale, flavon exchange can lead to interesting flavor-violating and CP violating effects. These are studied. It is found that d_e, mu -> e + gamma, and mu-e conversion on nuclei can be near present limits. For significant range of parameters mu-e conversion can be the most sensitive way to look for such effects.Comment: 19 pages, 5 Postscript figures, LATE