New Parametrization of Neutrino Mixing Matrix

Global fits to neutrino oscillation data are compatible with tri-bimaximal mixing pattern, which predicts $\theta_{23} = \frac{\pi}{4}, \theta_{12} = \sin^{-1} (\frac{1}{\sqrt{3}})$ and $\theta_{13} = 0$. We propose here to parametrize the tri-bimaximal mixing matrix $V_{TBM}$ by its hermitian generator $H_{TBM}$ using the exponential map. Then we use the exponential map to express the deviations from tri-bimaximal pattern by deriving the hermitian matrices $H_{z=0}$ and $H_1$. These deviations might come from the symmetry breaking of the neutrino and charged lepton sectors.Comment: 10 pages, no figures, correted minor typo

Model for a Light Z' Boson

A model of a light $Z'$ boson is constructed and phenomenological bounds are derived. This $Z'$ boson arises from a very simple extension to the Standard Model, and it is constrained to be light because the vacuum expectation values which generate its mass also break the electroweak gauge group. It is difficult to detect experimentally because it couples exclusively or primarily (depending on symmetry breaking details) to second and third generation leptons. However, if the $Z'$ boson is sufficiently light, then there exists the possibility of the two-body decay $\tau \rightarrow \mu Z'$ occuring. This will provide a striking signature to test the model.Comment: 20 pages + 5 pages of figures (appended as postscipt files), LaTeX, OITS-53

Topological phase due to electric dipole moment and magnetic monopole interaction

We show that there is an anologous Aharonov-Casher effect on a neutral particle with electric dipole moment interacting with a magnetic filed produced by magnetic monopoles.Comment: 8 page

Collective Modes in the Loop Ordered Phase of Cuprates

We show that the two branches of collective modes discovered recently in under-doped Cuprates with huge spectral weight are a necessary consequence of the loop-current state. Such a state has been shown in earlier experiments to be consistent with the symmetry of the order parameter competing with superconductivity in four families of Cuprates. We also predict a third branch of excitations and suggest techniques to discover it. Using parameters to fit the observed modes, we show that the direction of the effective moments in the ground state lies in a cone at an angle to the c-axis as observed in experiments

Hints of Standard Model Higgs Boson at the LHC and Light Dark Matter Searches

The most recent results of searches at the LHC for the Higgs boson h have turned up possible hints of such a particle with mass m_h about 125 GeV consistent with standard model (SM) expectations. This has many potential implications for the SM and beyond. We consider some of them in the contexts of a simple Higgs-portal dark matter (DM) model, the SM plus a real gauge-singlet scalar field D as the DM candidate, and a couple of its variations. In the simplest model with one Higgs doublet and three or four generations of fermions, for D mass m_D DD tends to have a substantial branching ratio. If future LHC data confirm the preliminary Higgs indications, m_D will have to exceed m_h/2. To keep the DM lighter than m_h/2, one will need to extend the model and also satisfy constraints from DM direct searches. The latter can be accommodated if the model provides sizable isospin violation in the DM-nucleon interactions. We explore this in a two-Higgs-doublet model combined with the scalar field D. This model can offer a 125-GeV SM-like Higgs and a light DM candidate having isospin-violating interactions with nucleons at roughly the required level, albeit with some degree of fine-tuning.Comment: 17 pages, 4 figures, slightly revised, main conclusions unchanged, references added, matches published versio

SU(2) gluon propagator on a coarse anisotropic lattice

We calculated the SU(2) gluon propagator in Landau gauge on an anisotropic coarse lattice with the improved action. The standard and the improved scheme are used to fix the gauge in this work. Even on the coarse lattice the lattice gluon propagator can be well described by a function of the continuous momentum. The effect of the improved gauge fixing scheme is found not to be apparent. Based on the Marenzoni's model, the mass scale and the anomalous dimension are extracted and can be reasonably extrapolated to the continuum limit with the values $\alpha\sim 0.3$ and $M\sim 600MeV$. We also extract the physical anisotropy $\xi$ from the gluon propagator due to the explicit $\xi$ dependence of the gluon propagator.Comment: LaTeX, 14 pages including 4 ps figure