Electroweak scale seesaw and heavy Dirac neutrino signals at LHC
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ElectroweakDirac neutrinoLHC (Large Hadron Collider)
Águila, F.; Aguilar-Saavedra, J.A. Electroweak scale seesaw and heavy Dirac neutrino signals at LHC. Physics Letters B, 672(2): 158-165 (2009). [http://hdl.handle.net/10481/30594]
PatrocinadorThis work has been supported by MEC project FPA2006-05294 and Junta de Andalucía projects FQM 101, FQM 437 and FQM03048. The work of J.A.A.S. has been supported by a MEC Ramón y Cajal contract.
Models of type I seesaw can be implemented at the electroweak scale in a natural way provided that the heavy neutrino singlets are quasi-Dirac particles. In such case, their contribution to light neutrino masses has the suppression of a small lepton number violating parameter, so that light neutrino masses can arise naturally even if the seesaw scale is low and the heavy neutrino mixing is large. We implement the same mechanism with fermionic triplets in type III seesaw, deriving the interactions of the new quasi-Dirac neutrinos and heavy charged leptons with the SM fermions. We then study the observability of heavy Dirac neutrino singlets (seesaw I) and triplets (seesaw III) at LHC. Contrarily to common wisdom, we find that heavy Dirac neutrino singlets with a mass around 100 GeV are observable at the 5σ level with a luminosity of 13 fb−1. Indeed, in the final state with three charged leptons ℓ±ℓ±ℓ∓, not previously considered, Dirac neutrino signals can be relatively large and backgrounds are small. In the triplet case, heavy neutrinos can be discovered with a luminosity of 1.5 fb−1 for a mass of 300 GeV in the same channel.