Universality of Quark-Lepton Mass Matrix

The recently observed lepton mixing angle $\theta_{13}$ of the MNS mixing matrix is well incorporated in a universal mixing hypothesis between quark and lepton sectors. This hypothesis asserts that, in the charged lepton diagonal base, all other mass matrices for up- and down-type quarks and light neutrinos are diagonalized by the same unitary matrix except for the phase elements. It is expressed as $V_{CKM}= U_{MNS}(\delta^\prime)^\dagger P U_{MNS}(\delta)$ for quark mixing matrix $V_{CKM}$ and lepton mixing matrix $U_{MNS}(\delta)$ in the phenomenological level. Here $P$ is a diagonal phase mass matrix. $\delta^\prime$ is a slightly different phase parameter from the Dirac CP violating phase $\delta=1.1\pi$ (best fit) in the MNS lepton mixing matrix.Comment: 6 pages, 2 figures, accepted by MPL

Simple neutrino mass matrix with only two free parameters

A simple form of neutrino mass matrix which has only two free parameters is proposed from a phenomenological point of view. Using this mass matrix, we succeed to reproduce all the observed values for the MNS lepton mixing angles and the neutrino mass squared difference ratio. Our model also predicts $\delta_{\nu}= 155^\circ$ for the Dirac CP violating phase in the lepton sector and the effective neutrino mass $\langle m \rangle=6.3\times 10^{-3}$ eV in the neutrinoless double beta decay.Comment: 7 pages, 3 figure

Measuring the lower bound of the neutrino mass at the LHC in Higgs triplet model

We show in the framework of Higgs triplet model that the lower bound of the neutrino mass is obtained if we can measure $\frac{\Gamma(\Delta^{--}\to ee)}{\Gamma(\Delta^{--}\to \mu\mu)}$ at the LHC.Comment: 5 pages, 2 figures, revised version in Pyhs.Rev.D. Using the reduced luminosity of LHC, we added the estimation on the order of magnitude of the considering reaction

Simple mass matrices of neutrinos and quarks consistent with observed mixings and masses

We propose a simple phenomenological model of quarks-leptons mass matrices having fundamentally universal symmetry structure. These mass matrices consist of democratic and semi-democratic mass matrix terms commonly to the neutrino and the quark sectors and have only eight free parameters. We show that this mass matrix model well reproduces all the observed values of the MNS lepton and the CKM quark mixing angles, the neutrino mass squared difference ratio, and quark mass ratios, with an excellent agreement. The model also predicts $\delta_{CP}^\ell =-94^\circ$ for the leptonic $CP$ violating phase and $\langle m\rangle\simeq 0.0073$ eV for the effective Majorana neutrino mass.Comment: 10 pages, 3 figures. Accepted version by Physics Letters

Universal Texture of Quark and Lepton Mass Matrices

Against the conventional picture that the mass matrix forms in the quark sectors will take somewhat different structures from those in the lepton sectors, a possibility that all the mass matrices of quarks and leptons have the same form as in the neutrinos is investigated. For the lepton sectors, the model leads to a nearly bimaximal mixing with the prediction |U_{e3}|^2=m_e/2m_\mu=0.0024 and \tan^2\theta_{sol} \simeq m_{\nu 1}/m_{\nu 2}, and so on. For the quark sectors, it can lead to reasonable values of the CKM mixing matrix and masses: |V_{us}|\simeq \sqrt{m_d/m_s}, |V_{ub}| \simeq |V_{cb}|\sqrt{m_u/m_c}, |V_{td}| \simeq |V_{cb}|\cdot |V_{us}|, and so on.Comment: 9 pages, Latex, talk given at The 4th workshop on "Neutrino Oscillations and their Origin" (NOON2003) (Kanazawa, Japan, 10--14 Feb. 2002). To appear in the Proceeding

Constraints from Neutrinoless Double Beta Decay

We examine the constraints from the recent HEIDELBERG-MOSCOW double beta decay experiment. It leads us to the almost degenerate or inverse hierarchy neutrino mass scenario. In this scenario, we obtain possible upper bounds for the Majorana CP violating phase in the lepton sector by incorporating the data from the neutrino oscillation, the single beta decay experiments, and from the astrophysical observation. We also predict the neutrino mass that may be measurable in the future beta decay experiments.Comment: 10 pages, 3 figure

Constraints of mixing angles from neutrino oscillation experiments and neutrinoless double beta decay

From the analyses of the recent data of neutrino oscillation experiments (especially the CHOOZ and the Super KAMIOKANDE experiments), we discuss how these data affect the neutrinoless double beta decay ($(\beta \beta)_{0\nu}$) rate and vice versa assuming that neutrinos are Majorana particles. For the case that $m_1 \sim m_2 \ll m_3$ ($m_i$ are neutrino masses), we obtain, from the data of the CHOOZ and Super KAMIOKANDE, $0.28 \le \sin^2\theta_{23} \le 0.76$ and $\sin^2\theta_{13} \le 0.05$. Combining the latter constraint with the analysis of the "averaged" neutrino mass () appeared in $(\beta \beta)_{0\nu}$, we find that (\frac{-m_2}{m_3-m_2}<\sin^2 \theta_{13} \le 0.05), which leads to the constraint on () as ( \le 0.05 m_3+(1-0.05)m_2). For the case that $m_1 \ll m_2 \sim m_3$, we find that the data of neutrino oscillation experiments and$(\beta \beta)_{0\nu}$ imply the constraints of mixing angles.Comment: 12pp, LaTeX, 6 Figure