Extended technicolor contribution to the Zbb vertex

Abstract

We show that the flavor-diagonal gauge boson of the extended technicolor theory contributes with opposite sign to the standard model correction for the $Zbb$ vertex. This mechanism can naturally explain the deviation of the LEP result from the standard model prediction for the partial width $\Gamma (Z\to b\bar{b})$. A smaller value of the QCD coupling, ${\alpha }_s(m_Z)\simeq 0.115$, is then preferred by the $\Gamma (Z\to \text{mbox}hadron)$ data, which is consistent with both the recent Lattice-QCD estimate and the Particle Data Group average.

Comments: 12 pages, latex (using subeqnarray.sty), no figures