Signatures of Pseudo-goldstone Bosons in Technicolor Theories with the Gim Mechanism

One of the few phenomenologically viable technicolor (TC) scenarios are models that incorporate the GIM mechanism (TC-GIM). A large value of the top quark mass requires that the scale of extended-technicolor interactions is not much larger than 1 TeV. In many TC scenarios, this leads to unacceptably large flavor-changing neutral currents. Viable models should not violate the custodial SU(2) symmetry too strongly, in order to successfully predict the value of the ρ parameter. In TC-GIM models, extended-technicolor interactions are separated into three sectors corresponding to left-handed quarks and leptons, right-handed up sector and right-handed down sector. Due to this construction, TC-GIM theories possess a large GIM-like flavor symmetry, which guarantees that the flavor-changing neutral currents are sufficiently small. These models have only one electroweak doublet of technifermion fields, so their contribution to the S parameter is small. The custodial symmetry is preserved to a sufficient degree. In order to cancel anomalies, several fermion families beyond the ones in the Standard Model are needed in TC-GIM models. These fermions are confined by new gauge interactions. Below the confinement scale, the observable particles are pseudo-Goldstone bosons (PGBs) associated with spontaneous breaking of approximate chiral symmetries of these new interactions. We will describe the spectrum and the properties of these PGBs in a particular, socalled high-scale TC-GIM model . However, most of the properties are similar for the whole class of TC-GIM models. Note that in generic TC models PGBs are associated with chiral symmetry breaking by the technicolor gauge group. Here, they are due to extra confining interactions. There are two analogous sectors of PGBs in TC-GIM theories: one associated with the up quarks and neutral leptons, another with down quarks and charged leptons. We will focus on the down-type sector. The PGBs arise at a characteristic scale of confining interactions fS−1. This scale governs the