Abstract
We analyze constraints on a class of extended technicolor (ETC) models from neutral flavor-changing processes induced by (dimension-six) four-fermion operators. The ETC gauge group is taken to commute with the standard model gauge group. The models in the class are distinguished by how the left- and right-handed components of the quarks and charged leptons transform under the ETC group. We consider and other pseudoscalar meson mixings, and conclude that they are adequately suppressed if the and components of the relevant quarks are assigned to the same (fundamental or conjugate-fundamental) representation of the ETC group. Models in which the and components of the down-type quarks are assigned to relatively conjugate representations, while they can lead to realistic CKM mixing and intrafamily mass splittings, do not adequately suppress these mixing processes. We identify an approximate global symmetry that elucidates these behavioral differences and can be used to analyze other possible representation assignments. Flavor-changing decays, involving quarks and/or leptons, are adequately suppressed for any ETC representation assignment of the and components of the quarks, as well as the leptons. We draw lessons for future ETC model building.
- Received 3 September 2004
DOI:https://doi.org/10.1103/PhysRevD.70.093010
©2004 American Physical Society