Massive Color-Octet Bosons: Bounds on Effects in Top-Quark Pair Production

Understand

A critical survey of the existing direct and indirect constraints on massive spin-one color octets is presented.

• Since such new degrees of freedom appear in any extension of the color gauge group to a product of at least two SU(3) factors, we keep our discussion as independent as possible from the underlying theory.
• In the framework of scenarios that involve flavor non-universal couplings, we show that excessive flavor-changing neutral currents can be avoided by a suitable alignment in flavor space.
• Constraints from electroweak precision observables and direct production at hadron colliders still leave space for sizable new-physics effects in top-quark pair production, in particular a large forward-backward asymmetry.