https://doi.org/10.1140/epjp/s13360-024-05067-5
Regular Article
Helicity amplitudes in light-cone and Feynman-diagram gauges
1
Department of Physics, Jinan University, 510632, Guangzhou, Guangdong Province, China
2
Center for Theory and Computation, National Tsing Hua University, 300, Hsinchu, Taiwan
3
KEK Theory Center and Sokendai, 305-0801, Tsukuba, Ibaraki, Japan
4
Kavli IPMU (WPI), UTIAS, The University of Tokyo, 277-8583, Kashiwa, Chiba, Japan
5
Faculty of Education, Iwate University, 020-8550, Morioka, Iwate, Japan
6
Department of Physics and Astronomy, University of Kansas, 66045, Lawrence, KS, USA
Received:
24
November
2023
Accepted:
6
March
2024
Published online:
15
April
2024
Recently proposed Feynman-diagram (FD) gauge propagator for massless and massive gauge bosons is obtained from a light-cone (LC) gauge propagator, by choosing the gauge vector along the opposite direction of the gauge boson three-momentum. We implement a general LC gauge propagator for all the gauge bosons of the standard model (SM) in the helicity amplitude subroutines (HELAS) codes, such that all the SM helicity amplitudes can be evaluated at the tree level in the LC gauge by using MadGraph. We confirm that our numerical codes produce helicity amplitudes which agree among all gauge choices. We then study interference patterns among Feynman amplitudes, for a few 
scattering processes in QED and QCD, and the process 
followed by the 
decays. We find that the particular choice of the FD gauge vector has advantages over generic LC gauge, not only because all the terms which grow with energy of off-shell and on-shell currents are removed systematically from all the diagrams, but also because no artificial gauge vector direction dependence of individual amplitudes appears.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2024. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
