Anatomy of Top-Mode Extended Technicolor Model

TL;DR

This paper analyzes extended technicolor models incorporating topcolor to generate realistic top quark mass, revealing the importance of anomalous dimensions and proposing a twisted model with enhanced quark mass generation.

Contribution

It introduces a twisted topcolor-assisted technicolor model with large anomalous dimensions that enhances quark masses and predicts a universal upper bound on the top-pion mass.

Findings

The straightforward model yields too small third-generation masses.

The twisted model achieves realistic quark masses via large anomalous dimensions.

Top-pion mass is bounded above by 70 GeV in the model.

Abstract

We analyze two versions of the extended technicolor (ETC) incorporating the top quark condensate via the flavor-universal coloron type topcolor $SU(3)_1 \times SU(3)_2$: A straightforward top-mode ETC having quarks and techniquarks assigned to a single (strong) $SU(3)_1$, and a ``twisted model'' with techniquarks carrying the weak $SU(3)_2$ while quarks the strong $SU(3)_1$. The straightforward model has the same ETC structure as that of Appelquist et al. without topcolor which we first analyze to find that it yields only too small ETC-induced mass for the third generation. In contrast, our model having topcolor takes the form of a version of the topcolor-assisted technicolor (TC2) after ETC breakings, which triggers the top quark condensate giving rise to a realistic top mass. However, techniquarks have the strong topcolor $SU(3)_1$ in addition to the already strong walking/conformal technicolor, which triggers the techniquark condensate at scale much higher than the weak scale, a disaster. We then consider a ``twisted model'' of TC2, though not an explicit ETC. We find a new feature that ``ETC''-induced quark mass is enhanced to the realistic value by the large anomalous dimension $\gamma_m \simeq 2$ of Nambu-Jona-Lasinio-type topcolor interactions. The result roughly reproduces the realistic quark masses. We further find a novel effect of the above large anomalous dimension $\gamma_m \simeq 2$: The top-pion mass has a universal upper bound, $m_{\pi_t} < 70 \GeV$, in the generic TC2 model.