Phenomenology of the neutrino physics in Kaluza-Klein theories of low-scale quantum gravity

por Dr. Ara Ioannisian (IFIC and Yerevan Univ.)

jueves 14 sept. 2000 11:30 → 12:30 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

We discuss phenomenology of the neutrino physics in Kaluza-Klein theories of low-scale quantum gravity. We show that one-loop effects induced by Kaluza-Klein neutrinos, albeit tiny individually, act cumulatively in electroweak processes, giving rise to a non-decoupling behaviour for large values of the higher-dimensional Yukawa couplings. Owing to the non-decoupling effects of Kaluza-Klein neutrinos, we can derive stronger constraints on the parameters of the theory that originate from the non-observation of flavour-violating and universality-breaking phenomena, which involve the W and Z bosons, and the e, $\mu$ and $\tau$ leptons. In this theory we propose a four-neutrino model which can reconcile the existing data coming from underground experiments in terms of neutrino oscillations, together with the hint from the LSND experiment and a possible neutrino contribution to the hot dark matter of the Universe. Our fourth light neutrino $\nu_s$ ($s$ for sterile) is identified with the zero mode of the Kaluza-Klein states. It combines with one of the active neutrinos in order to form a Quasi--Dirac neutrino with mass in the eV range. On the other hand the solar and atmospheric mass scales arise from the violation of the fermion number on distant branes.