Leptogenesis in the μτ basis

Abstract

Abstract We formulate three-flavor type-I leptogenesis in the μτ basis which is convenient because in the three-flavor regime, both μ and τ charged lepton Yukawa interactions are in thermal equilibrium and the thermal bath is symmetric under the exchange μ ↔ τ . We apply this formalism to models with μτ -reflection CPμτ symmetry. We confirm the previous result that leptogenesis fails in the three-flavor regime with exact CPμτ symmetry. Allowing CPμτ symmetry to be broken to various degrees, we show that leptogenesis can be successful in the three-flavor regime only in certain tuned parameter space, which could further imply additional symmetry is at play. As a bonus, we derive analytical expressions which could be utilized whenever the branching ratios for the decays to μ and τ flavors are equal or approximately so.