Meeting the Constraint of Neutrino-Higgsino Mixing in Gravity Unified Theories

Abstract

In Gravity Unified Theories all operators that are consistent with the local gauge and discrete symmetries are expected to arise in the effective low-energy theory. Given the absence of multiplets like 126 of SO(10) in string models, and assuming that B-L is violated spontaneously to generate light neutrino masses via a seesaw mechanism, it is observed that string theory solutions generically face the problem of producing an excessive ${\nu }_L-\tilde{H}$ mixing mass at the GUT scale, which is some nineteen orders of magnitude larger than the experimental bound of 1 MeV. The suppression of ${\nu }_L-\tilde{H}$ mixing, like proton longevity, thus provides one of the most severe constraints on the validity of any string theory solution. We examine this problem in a class of superstring derived models. We find a family of solutions within this class for which the symmetries of the models and an allowed pattern of VEVs, surprisingly, succeed in adequately suppressing the neutrino-Higgsino mixing terms. At the same time they produce the terms required to generate small neutrino masses via a seesaw mechanism.

18 pages. Standard Latex

Cited by in corpus (6)

• Toward the classification of the realistic free fermionic models
• String Inspired Neutrino Mass Textures in Light of KamLAND and WMAP
• A Family--Universal Anomalous U(1) in String Models as the Origin of Supersymmetry Breaking and Squark Degeneracy
• String Inspired Z' Model With Stable Proton and Light Neutrino Masses
• With Neutrino Masses Revealed, Proton Decay is the Missing Link
• Hybrid MSW + VO Solution of the Solar Neutrino Problem in String-Motivated Unified Theories