Goldstone Bosons in the Appelquist-Terning ETC Model

Abstract

It is demonstrated that the extended technicolor model proposed recently by Appelquist and Terning has pair of potentially light $U(1)$ Goldstone bosons coupling to ordinary matter with strength $\frac{2m_f}{F_{\pi }}$, where $m_f$ is the mass of the fermion and $F_{\pi }\approx 125\text{GeV}$. These Goldstone bosons could get a mass if the spontaneously broken $U(1)$ symmetries are also explicitly broken, by physics beyond that specified in the model. An attempt to break these symmetries by embedding the model into a larger gauge group seems to be inadequate. The problem is because there are too many representations and there is a mismatch between the number of condensates and the number of gauge symmetries broken.

Comments: 14 pages, uses harvmac, to be published in Phys. Rev. D