Single-minus gluon tree amplitudes are nonzero
TL;DR
Imagine tiny particles called gluons are like spinning tops. Their spin can be in one of two directions, which physicists call 'plus' or 'minus'. For decades, the rulebook seemed to say that you could never have a situation where just one gluon was spinning 'minus' and all the others were spinning 'plus' — that outcome was thought to be zero. This paper found a loophole. Under very specific, purely mathematical conditions that don't exist in our physical reality but are useful for calculations, this interaction can happen. The researchers wrote down the exact recipe for it, fixing a small but important detail in our fundamental rulebook for how the universe works.
Single-minus tree-level $n$-gluon scattering amplitudes are reconsidered. Often presumed to vanish, they are shown here to be nonvanishing for certain "half-collinear" configurations existing in Klein space or for complexified momenta. We derive a piecewise-constant closed-form expression for the decay of a single minus-helicity gluon into $n-1$ plus-helicity gluons as a function of their momenta. This formula nontrivially satisfies multiple consistency conditions including Weinberg's soft theorem.
- 1Single-minus tree-level $n$-gluon amplitudes are nonzero for certain configurations.
- 2Derived a closed-form expression for single minus-helicity gluons.
- 3Expression satisfies multiple consistency conditions including Weinberg's theorem.
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