Strangeness-changing processes and the limit on the right-handed gauge-boson mass

We study strangeness-changing processes, in particular, the $K_L-K_S$ mass difference and $K\to 2\pi$ decays, in the context of left-right-symmetric gauge theories in a search for a lower bound on a scale of parity-breaking $M_R$. We find that the previously claimed limit on $M_R$ is a function of Higgs-boson masses and also the top-quark mass and its mixings to lighter quarks. For the light $t$ quark ($M_t\le 30$ GeV), we get $M_R>200\mathrm{}$ GeV (for $m_H\simeq 100$ GeV), and the bound goes down with the increasing $t$-quark mass. Even in the case of a very heavy neutral Higgs boson ($m_H\simeq 1$ TeV), the lower limit on $M_R$ is only ∼400 GeV. We argue that the best limits on $M_R$ must come from neutral-current phenomena.