Effective interactions and on-shell recursion relation for massive spin 3/2

Aug 28, 2024
46 pages
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Report number:
  • UMN-TH-4332/24,FTPI-MINN-24-19

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Abstract: (arXiv)
We use on-shell methods to compute all three-point interactions of massive spin-3/2 particles involving a graviton and particles of spin 1\leq 1. By employing the massive spinor-helicity formalism we identify the interactions which have a smooth massless limit as expected from the superHiggs mechanism. These interactions are then used to on-shell construct four-point massive spin-3/2 amplitudes using an all-line transverse shift for the external momenta, which correctly reproduces the contact gravitino interactions in the N=1N=1 supergravity Lagrangian. The on-shell constructed four-point amplitudes are also used to derive well-known unitarity bounds in supergravity. In particular, by adding scalar and pseudoscalar interactions to construct the four-point massive spin-3/2 amplitudes that scale as E2E^2 in the high-energy limit, we recover the on-shell Polonyi model with a Planck scale unitarity bound. These effective three-point interactions and on-shell recursion relations provide an alternative and simpler way to study the interactions of massive spin-3/2 particles without a Lagrangian or the use of Feynman diagrams.
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  • 46 pages
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