Helicity amplitudes for QCD with massive quarks

TL;DR

This paper applies a new massive spinor-helicity formalism to compute specific tree-level QCD scattering amplitudes involving a massive quark pair and multiple gluons, allowing flexible spin quantization.

Contribution

It provides explicit all-multiplicity formulas for QCD amplitudes with massive quarks using the novel formalism, extending previous results to arbitrary spin projections.

Findings

Derived formulas for amplitudes with all gluons identical helicity

Derived formulas for amplitudes with one opposite-helicity gluon adjacent to a quark

Results include known amplitudes for fixed spin quantization axes

Abstract

The novel massive spinor-helicity formalism of Arkani-Hamed, Huang and Huang provides an elegant way to calculate scattering amplitudes in quantum chromodynamics for arbitrary quark spin projections. In this note we compute two families of tree-level QCD amplitudes with one massive quark pair and n-2 gluons. The two cases include all gluons with identical helicity and one opposite-helicity gluon being color-adjacent to one of the quarks. Our results naturally incorporate the previously known amplitudes for both quark spins quantized along one of the gluonic momenta. In the all-multiplicity formulae presented here the spin quantization axes can be tuned at will, which includes the case of the definite-helicity quark states.