Neutrino Masses Without Seesaw Mechanism in a SUSY SU(5) Model With Additional ${\bar{5}}_L^{\prime }+5_L^{\prime }$

Abstract

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 ${\bar{5}}_L^{\prime }+5_L^{\prime }$ 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 ${\bar{H}}_d{\bar{5}}_L^{\prime }10_L$. Since the matter fields ${\bar{5}}_L^{\prime }$ 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 ${\bar{5}}_L^{\prime }\leftrightarrow {\bar{5}}_L$ 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.

Comments: 4 pages, 1 figure, talk at ICHEP2004, to appear in Proceedings