Gauge invariance from on-shell massive amplitudes and tree-level unitarity

Apr 27, 2022
50 pages
Published in:
  • Phys.Rev.D 106 (2022) 7, 076003
  • Published: Oct 1, 2022
e-Print:
DOI:
Report number:
  • UUITP-23/22

Citations per year

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Abstract: (APS)
We study the three-particle and four-particle scattering amplitudes for an arbitrary, finite number of massive scalars, spinors and vectors by employing the on-shell massive spinor formalism. We consider the most general three-particle amplitudes with energy-growing behavior at most of O(E). This is the special case of the requirement of tree unitarity, which states that the N-particle scattering amplitudes at tree level should grow at most as O(E4-N) in the high-energy hard-scattering limit, i.e., at fixed nonzero angles. Then the factorizable parts of the four-particle amplitudes are calculated by gluing the on-shell three-particle amplitudes together and utilizing the fact that tree-level amplitudes have only simple poles. The contact parts of the four-particle amplitudes are further determined by tree unitarity, which also puts strong constraints on the possible allowed three-particle coupling constants and the masses. The derived relations among them converge to the predictions of gauge invariance in the UV theory. This provides a purely on-shell understanding of spontaneously broken gauge theories.
Note:
  • 39 pages + appendices; matched to the published version in v2
  • invariance: gauge
  • energy: high
  • spinor: massive
  • unitarity
  • tree approximation
  • scattering amplitude
  • gauge field theory
  • spontaneous symmetry breaking
  • hard scattering
  • pole