Extended Technicolor Models with Two ETC Groups

摘要

We construct extended technicolor (ETC) models that can produce the largesplitting between the masses of the $t$ and $b$ quarks without necessarilyexcessive contributions to the $\rho$ parameter or to neutral flavor-changingprocesses. These models make use of two different ETC gauge groups, such thatleft- and right-handed components of charge $Q=2/3$ quarks transform under thesame ETC group, while left- and right-handed components of charge -1/3 quarksand charged leptons transform under different ETC groups. The models therebysuppress the masses $m_b$ and $m_\tau$ relative to $m_t$, and $m_s$ and $m_\mu$relative to $m_c$ because the masses of the $Q=-1/3$ quarks and charged leptonsrequire mixing between the two ETC groups, while the masses of the $Q=2/3$quarks do not. A related source of the differences between these masssplittings is the effect of the two hierarchies of breaking scales of the twoETC groups. We analyze a particular model of this type in some detail. Althoughwe find that this model tends to suppress the masses of the first twogenerations of down-type quarks and charged leptons too much, it gives usefulinsights into the properties of theories with more than one ETC group.