where Y u , Y d , and Y e are 3 × 3 matrices of Yukawa couplings, with the mn term giving the coupling of the generations m and n, and h.c. means Hermitian conjugate of preceding terms. The fields Q L and ℓ ℓ L are left-handed quark and lepton doublets. Likewise, u R , d R and e R are right-handed up-type quark, down-type quark, and lepton singlets. Finally φ φ is the Higgs doublet and φ φ ~ ~ = i τ τ 2 φ φ ∗ ∗ is its charge conjugate state.