Flavor effects in leptogenesis

Abstract

Flavor effects can have a significant impact on the final estimate of the lepton (and therefore baryon) asymmetry in scenarios of leptogenesis. It is therefore necessary to account fully for this flavor dynamics in the relevant transport equations that describe the production (and washout) of the asymmetry. Doing so can both open up and restrict viable regions of parameter space relative to the predictions of more approximate calculations. In this review, we identify the regimes in which flavor effects can be relevant and illustrate their impact in a number of phenomenological models. These include type I and type II seesaw embeddings, and low-scale resonant scenarios. In addition, we provide an overview of the semi-classical and field-theoretic methods that have been developed to capture flavor effects in a consistent way.b Here, we have taken the right-handed charged leptons to live in their flavor basis, which we can always do without the need to rotate other couplings. This is, of course, different for the doublet leptons, which have SM Yukawa coupling, as well as couplings to RH neutrinos, that cannot be simultaneously diagonalized. A flavor-covariant description of the right-handed charged leptons is presented in Ref. [41].

Why is there more matter than antimatter? Calculational methods for leptogenesis and electroweak baryogenesis

“…Given the large number of possible scenarios for baryogenesis and variants thereof a comprehensive phenomenological survey of the field would require a far more extensive treatment than is offered in this work. We note nonetheless that recently, a series of review articles on leptogenesis has appeared that provides some comprehensive, yet detailed, review of the state of the art [34][35][36][37][38][39]. The present article presents basic elements necessary in order to set up some minimal fluid equations for baryogenesis, and it additionally justifies these equations in a more detailed way based on the CTP methods.…”

Fitting high-energy Littlest Seesaw parameters using low-energy neutrino data and leptogenesis

“…and N (K α ) = 3π K α 4 , where K α is the decay parameter [55]. For the flavourdependent case this will become K 2 , combining the e and µ decay parameters.…”

Flavor physics without flavor symmetries

“…However, for the heavy Majorana masses given in Table III, the baryon asymmetry calculated from Eqs. (23)- (25) can be modified by flavor effects of charged leptons and other heavy neutrinos by more than an order of magnitude [61,62]. To obtain a realistic estimate of the baryon asymmetry, the flavor effects of charged leptons and in particular the contributions of the heavier Majorana neutrinos have to be taken into account.…”