Neutrino Oscillations: from Standard and Non-standard Viewpoints

In the standard model of neutrino oscillations, the neutrino flavor states are mixtures of mass-eigenstates, and the phenomena are well described by the neutrino mixing matrix, i.e., the PMNS matrix. I review the recent progress on parametrization of the neutrino mixing matrix. Besides that I also discuss on the possibility to describe the neutrino oscillations by a non-standard model in which the neutrino mixing is caused by the Lorentz violation (LV) contribution in the effective field theory for LV. We assume that neutrinos are massless and that neutrino flavor states are mixing states of energy eigenstates. In our calculation the neutrino mixing parts depend on LV parameters and neutrino energy. The oscillation amplitude varies with the neutrino energy, thus neutrino experiments with energy dependence may test and constrain the Lorentz violation scenario for neutrino oscillation.Comment: 6 pages, Talk presented at CosPA2008, published in Proceedings of the International Symposium on Cosmology and Particle Astrophysics; Pohang, Korea, 28 October - 1 November 2008; Editor: Sang Pyo Ki

NuTeV Anomaly & Strange-Antistrange Asymmetry

The NuTeV Collaboration reported a value of $\sin^{2}\theta_{w}$ measured in neutrino-nucleon deep inelastic scattering, and found that the value is three standard deviations from the world average value of other electroweak measurements. If this result cannot be explained within conventional physics, it must imply some novel physics beyond the standard model. We report the correction from the asymmetric strange-antistrange sea by using both the light-cone baryon-meson fluctuation model and the chiral quark model, and show that a significant part of the NuTeV anomaly can be explained by the strange-antistrange asymmetry.Comment: 4 pages, 2 figures. Talk at ICHEP04, August 16-22, 2004, Beijing, Chin

The Phantom of the OPERA: Superluminal Neutrinos

This report presents a brief review on the experimental measurements of the muon neutrino velocities from the OPERA, Fermilab and MINOS experiments and that of the (anti)-electron neutrino velocities from the supernova SN1987A, and consequently on the theoretical attempts to attribute the data as signals for superluminality of neutrinos. Different scenarios on how to understand and treat the background fields in the effective field theory frameworks are pointed out. Challenges on interpreting the OPERA result as a signal of neutrino superluminality are briefly reviewed and discussed. It is also pointed out that a covariant picture of Lorentz violation may avoid the refutation on the OPERA experiment.Comment: 10 latex pages. Final version for journal publicatio

The x-Dependent Helicity Distributions for Valence Quarks in Nucleons

We derive simple relations between the polarized and unpolarized valence quark distributions in a light-cone SU(6) quark-spectator model for nucleons. The explicit x-dependent Wigner rotation effect for the light-flavor quarks is calculated. It is shown that the mass difference between the scalar and vector spectators could reproduce the up and down valence quark asymmetry that accounts for the observed ratio $F_2^{n}/F_2^{p}$. The proton, neutron, and deuteron polarization asymmetries, $A_1^p$, $A_1^n$, and $A_1^d$, are in agreement with the available data by taking into account the Wigner rotation effect. The calculated $x$-dependent helicity distributions of the up and down valence quarks are compared with the recent results from semi-inclusive hadron asymmetries in polarized deep inelastic scattering by the Spin Muon Collaboration.Comment: 20 pages, latex, with 4 postscript figures, to be published in Phys.Lett.B, small corrections to reference

Simple parametrization of neutrino mixing matrix

We propose simple forms of neutrino mixing matrix in analogy with the Wolfenstein parametrization of quark mixing matrix, by adopting the smallest mixing angle $\theta_{13}$ as a measure of expansion parameters with the tribimaximal pattern as the base matrix. The triminimal parametrization technique is utilized to expand the mixing matrix under two schemes, i.e., the standard Chau-Keung (CK) scheme and the original Kobayashi-Maskawa (KM) scheme. The new parametrizations have their corresponding Wolfenstein-like parametrizations of quark mixing matrix, and therefore they share the same intriguing features of the Wolfenstein parametrization. The newly introduced expansion parameters for neutrinos are connected to the Wolfenstein parameters for quarks via the quark-lepton complementarity.Comment: 5 pages. Version for publication in PR