Fourth-generation quark masses and Fritzsch mass matrices from Abelian family symmetry.

Abstract

We examine possible mass relations resulting from Fritzsch-type mass matrices for quarks in left-right-symmetric models with an Abelian family symmetry. While the three-generation model predicts no realistic mass relation, six possible schemes exist in the presence of a fourth generation of quarks (t',b'), with realistic constraints on the quark masses. The most attractive scheme predicts (${m}_{b\mathcal{'}}$-${m}_{b}$)(${m}_{t\mathcal{'}}$-${m}_{t}$)\ensuremath{\simeq}(${m}_{\mathrm{sb}}$${m}_{b}$${\mathcal{'}}_{\mathrm{ct}\mathcal{'}}^{13}$@B. When combined with the experimental constraints on the \ensuremath{\rho} parameter, this leads to ${m}_{t}$\ensuremath{\le}68 GeV, ${m}_{b\mathcal{'}}$\ensuremath{\le}46 GeV, and 145 GeV\ensuremath{\le}${m}_{t\mathcal{'}}$\ensuremath{\le}310 GeV.