KL→2μ,KL→2γ, and quark masses in gauge models

Abstract

Experimental knowledge of the decay rates for $K_L\to 2\mu$ and $K_L\to 2\gamma$ is combined with theoretical understanding of strangeness-changing neutral-current effects in unified gauge models of the weak and electromagnetic interactions for a determination of quark masses. Given that the Weinberg parameter ${sin}^2{\theta }_W$ is between 0.3 and 0.4, the mass of the proton quark becomes roughly 900 MeV, while that of the "charmed" quark is about 5 GeV.