Neutrino Masses at v^{3/2}
Nima Arkani-Hamed, Lawrence Hall, Hitoshi Murayama, David Smith, Neal Weiner
TL;DR
The paper investigates how neutrino masses can arise in gravity-mediated SUSY frameworks by treating the intermediate SUSY-breaking scale $m_I$ as the small parameter, aiming to explain atmospheric and solar neutrino data without a conventional high-scale see-saw. It presents two viable $O(m_I^3)$ mechanisms: (i) a simple tree-level construction with a weak-scale right-handed neutrino and Dirac masses suppressed by flavor factors, producing $m_ u \,\sim\, m_I^3$ (or $\lambda_\tau^2 m_I^3$), and (ii) a radiative scenario where hidden-sector vevs and Planck-suppressed operators yield a loop-induced $m_ u$ at the same order. The framework yields rich phenomenology, including the possibility of sneutrino dark matter, and demonstrates that $m_I$-driven neutrino masses can naturally reproduce the observed light-neutrino scale without invoking ultra-high mediation scales. These results offer a distinct route to neutrino mass generation with testable SUSY signatures.
Abstract
Theories in which neutrino masses are generated by a conventional see-saw mechanism generically yield masses which are O(v^2) in units where M_{Pl}=1, which is naively too small to explain the results from SuperKamiokande. In supersymmetric theories with gravity mediated supersymmetry breaking, the fundamental small parameter is not v/M_{Pl}, but m_I/M_{Pl}, where m_I is the scale of supersymmetry breaking in the hidden sector. We note that m_I^3/M_{Pl}^2 is only slightly too large to explain SuperKamiokande, and present two models that achieve neutrino masses at this order in m_I, one of which has an additional suppression lambda_tau^2, while the other has additional suppression arising from a loop factor. The latter model shares a great deal of phenomenology with a class of models previously explored, including the possibility of viable sneutrino dark matter.