Reconciliation of CDM abundance and $\mu\to e\gamma$ in a radiative seesaw model

Understand

We reexamine relic abundance of a singlet fermion as a CDM candidate, which contributes to the neutrino mass generation through radiative seesaw mechanism.

• We search solutions for Yukawa couplings and the mass spectrum of relevant fields to explain neutrino oscillation data.
• For such solutions, we show that an abundance of a lightest singlet fermion can be consistent with WMAP data without conflicting with both bounds of $\mu\to e\gamma$ and $\tau\to \mu\gamma$.
• This reconciliation does not need any modification of the original radiative seesaw model other than by specifying flavor structure of Yukawa couplings and taking account of coannihilation effects.