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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2409.08099 |
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Table of Contents:
- We present a procedure g5anchor to anchor $γ_5$ in the definition of a Dirac trace with $γ_5$ in Dimensional Regularization (DR) in Feynman diagrams for the Standard Model, based on a recent revision of the works by Kreimer, Gottlieb and Donohue. For each closed fermion chain with an odd number of primitive (i.e.~not-yet-clearly-defined) $γ_5$ in a given Feynman diagram, g5anchor returns a definite set of anchor points for $γ_5$, in terms of pairs of ordered fermion propagators; at each of these $γ_5$ anchor points a fixed expression in terms of the Levi-Civita tensor and elementary Dirac matrices will be inserted together with a sign determined by anticommutatively shifting all $γ_5$ from their original places (dictated by the Feynman rules) to this anchor point. The defining expressions for the cyclic $γ_5$-odd Dirac traces in DR associated with closed fermion chains in amplitudes, or more generally squared amplitudes, thus follow from this procedure, where the Levi-Civita tensors are not necessarily treated strictly in 4-dimensions. We propose utilizing this definition in practical perturbative calculations in the Standard Model at least to two-loop orders with the current implementation. Certain limitations and modifications of the KKS and/or the Kreimer scheme are addressed, as well as the possible caveats with g5anchor.