Non-unitary neutrino mixing from an extra-dimensional seesaw model
2010 (English)Manuscript (preprint) (Other academic)
We study the generation of light neutrino masses in an extra-dimensional model, where right-handed neutrinos are allowed to propagate in the extra dimension, while the Standard model (SM) particles are confined to a brane. Motivated by the fact that extra-dimensional models are non-renormalizable, we truncate the Kaluza–Klein (KK) towers at a maximal KK index. The structure of the bulk Majorana mass term, motivated by the Sherk–Schwarz mechanism, implies that the right-handed KK neutrinos pair to form Dirac neutrinos, except for a number of unpaired Majorana neutrinos at the top of each tower. These heavy Majorana neutrinos are the only sources of lepton number breaking in the model, and similarly to the type-I seesaw mechanism, they naturally generate small masses for the left-handed neutrinos. The lower KK modes mix with the light neutrinos, and the mixing effects are not suppressed with respect to the light neutrino masses. Compared to conventional fermionic seesaw models, the non-unitary effects induced by such mixing are quite significant. We study the signals of this model at the Large Hadron Collider (LHC), and find that the current bounds on the non-unitarity parameters are strong enough to exclude an observation.
Place, publisher, year, edition, pages
IdentifiersURN: urn:nbn:se:kth:diva-31716OAI: oai:DiVA.org:kth-31716DiVA: diva2:406049
FunderSwedish Research Council, 621-2008-4210EU, FP7, Seventh Framework Programme
QC 20110324. Manuskriptet har uppdaterats och publicerats som "Signatures from an extra-dimensional seesaw model" i PHYSICAL REVIEW D, 2010, Vol 82,Issue 4.
The submitted manuscript has been peer-reviewed and published under the title "Signatures from an extra-dimensional seesaw model" in PHYSICAL REVIEW D, 2010, Vol 82,Issue 4.2011-06-212011-03-242012-03-15Bibliographically approved