Yukawas and Neutrinos at Infinite Distance

Abstract: We study limits of vanishing Yukawa couplings of 4d chiral matter fields in Quantum Gravity, using as a laboratory type IIA orientifolds with D6-branes. In these theories chiral fermions arise at brane intersections, where an infinite tower of charged particles are localized. We show that in the limit Y → 0 some of these towers become asymptotically massless, while at the same time the kinetic term of some chiral fields becomes singular and at least two extra dimensions decompactify. Moreover, in this limit some of the gauge couplings associated to the Yukawa vanish. We apply these results to the case of Dirac neutrino masses, which require tiny Yukawa couplings. We find Dirac neutrino masses of the form m_v ≃ g_ν ⟨H⟩, with g_ν the gauge coupling of the massive anomalous U (1) under which the right-handed neutrinos are charged, and which should be in the range g_ν ≃ 10^−13 to reproduce neutrino data. We also describe the difficulties in obtaining appropriate tiny neutrino Yukawas in the cases of a single or more than two large dimensions. Thus the case with two large dimensions seems to be quite unique in order to get Dirac neutrino masses.

general relativity and quantum cosmologyHEP - phenomenologyHEP - theorymathematical physicsquantum physics

Audience: researchers in the topic

High Energy Theory NYU Abu Dhabi