Neutrino Masses Without Seesaw Mechanism in a SUSY SU(5) Model With Additional 5ˉL′+5L′\bar{5}'_L+5'_L

A radiatively-induced neutrino mass matrix with a simple structure is proposed on the basis of an SU(5) SUSY GUT model with R-parity violation. The model has matter fields $\bar{5}'_{L}+5'_{L}$ in addition to the ordinary matter fields $\bar{5}_{L}+10_{L}$ and Higgs fields $H_u+\bar{H}_d$. The R-parity violating terms are given by $\bar{5}_{L} \bar{5}_{L} 10_{L}$, while the Yukawa interactions are given by $\bar{H}_d \bar{5}'_{L} 10_{L}$. Since the matter fields $\bar{5}'_L$ and $\bar{5}_L$ are different from each other at the unification scale, the R-parity violation effects at a low energy scale appear only through the $\bar{5}'_L \leftrightarrow \bar{5}_{L}$ mixings. In order to make this R-parity violation effect harmless for proton decay, a discrete symmetry Z_3 and a triplet-doublet splitting mechanism analogous to the Higgs sector are assumed.Comment: 4 pages, 1 figure, talk at ICHEP2004, to appear in Proceeding

Another Formula for the Charged Lepton Masses

A charged lepton mass formula $(m_e +m_\mu + m_\tau)/(\sqrt{m_e}+\sqrt{m_\mu} + \sqrt{m_\tau})^2 =2/3$ is well-known. Since we can, in general, have two relations for three quantities, we may also expect another relation for the charged lepton masses. Then, the relation will be expressed by a form of $\sqrt{m_e m_\mu m_\tau}/(\sqrt{m_e}+\sqrt{m_\mu} + \sqrt{m_\tau})^3$. According to this conjecture, a scalar potential model is speculated.Comment: 5 pages, no figure; a typo in Eq.(7) correcte

Charged Lepton Mass Spectrum and a Scalar Potential Model

Stimulated by a recent work by Sumino, on the basis of a model in which effective Yukawa coupling constants are described by vacuum expectation values of a scalar $\Phi$ with $3\times 3$ components, a possible form of the scalar potential $V(\Phi)$ which can well describe the observed charged lepton mass spectrum is investigated without referring to a specific flavor symmetry model. A general relation among eigenvalues of is derived without referring to an explicit form of $V(\Phi)$.Comment: 9 pages, no figure, version to appear in Phys.Rev.

Neutrino Mass Hierarchies in a Mass Matrix Form Versus its Inverse Form

A neutrino mass matrix model M_\nu with M_\nu^T =M_\nu and a model with its inverse matrix form \widetilde{M}_\nu = m_0^2 (M_\nu^*)^{-1} can be diagonalized by the same mixing matrix U_\nu. It is investigated whether a scenario which provides a matrix model M_\nu with normal mass hierarchy can also give a model with an inverted mass hierarchy by considering a model with an inverse form of M_\nu.Comment: 6 pages, 4 figure

Structure of Right-Handed Neutrino Mass Matrix

Recently, Nishiura and the author have proposed a unified quark-lepton mass matrix model under a family symmetry U(3)$\times$U(3)$'$. The model can give excellent parameter-fitting to the observed quark and neutrino data. The model has a reasonable basis as far as the quark sector, but the form of the right-handed neutrino mass matrix $M_R$ does not have a theoretical grand, that is, it was nothing but a phenomenological assumption. In this paper, it is pointed out that the form of $M_R$ is originated in structure of neutrino mass matrix for $(\nu_i, N_\alpha)$ where $\nu_i$ ($i=1,2,3$) and $N_\alpha$ ($\alpha=1,2,3$) are U(3)-family and U(3)$'$-family triplets, respectively.Comment: 7 pages, no figur