Anthropic tuning of the weak scale and ofmu/mdin two-Higgs-doublet models

Abstract

It is shown that, in a model in which up-type and down-type fermions acquire mass from different Higgs doublets, the anthropic tuning of the Higgs mass parameters can explain the fact that the observed masses of the $d$ and $u$ quarks are nearly the same with $d$ slightly heavier. If Yukawa couplings are assumed not to scan (vary among domains), this would also help explain why $t$ is much heavier than $b$. It is also pointed out that the existence of dark matter invalidates some earlier anthropic arguments against the viability of domains where the standard model Higgs has positive ${\ensuremath{\mu}}^{2}$, but makes other even stronger arguments possible.