Speaker
Daniele Teresi
(University of Manchester)
Description
Flavour effects play an important role in the statistical evolution of particle number densities in several particle physics phenomena. We present a fully flavour-covariant formalism for transport phenomena, in order to consistently capure all flavour effects in the system. We explicitly study a Resonant Leptogenesis (RL) scenario, and show that flavour covariance requires one to consider generically off-diagonal number densities, rank-4 rate tensors in flavour space, and non-trivial generalization of the discrete symmetries $C$, $P$ and $T$.
The flavour-covariant transport equations, obtained in our semi-classical framework, describe the effect of three relevant physical phenomena: coherent heavy-neutrino oscillations, quantum decoherence in the charged-lepton sector, and the standard resonant $CP$ violation due to heavy-neutrino mixing. We show quantitatively that the final asymmetry is enhanced by up to an order of magnitude, for electroweak-scale heavy neutrinos, as compared to that obtained from flavour-diagonal or partially flavour off-diagonal equations.
A full field-theoretical treatment in the weakly-resonant regime, based on the so-called Kadanoff-Baym (KB) equations, confirms that heavy-neutrino oscillations and mixing are two *distinct* phenomena, and reproduces the results obtained in our semi-classical framework. Finally, we show that the quasi-particle ansaetze, often employed in KB approaches to RL, discard the phenomenon of mixing, capturing only oscillations and leading to an underestimate of the final asymmetry by a factor of order 2.
Authors
Apostolos Pilaftsis
(University of Manchester (GB))
Bhupal Dev
(University of Manchester)
Daniele Teresi
(University of Manchester)
Dr
Peter Millington
(Technische Universität München (TUM))
