Abstract
We study the space of 2 → 2 scattering amplitudes of neutral Goldstone bosons in four space-time dimensions. We establish universal bounds on the first two non-universal Wilson coefficients of the low energy Effective Field Theory (EFT) for such particles. We reconstruct the analytic, crossing-symmetric, and unitary amplitudes saturating our bounds, and we study their physical content. We uncover non-perturbative Regge trajectories by continuing our numerical amplitudes to complex spins. We then explore the consequence of additional constraints arising when we impose the knowledge about the EFT up to the cut-off scale. In the process, we improve on some aspects of the numerical S-matrix bootstrap technology for massless particles.
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Acknowledgments
We thank Miguel Correia, Aditya Hebbar, Sasha Monin, Francesco Riva, Biswajit Sahoo and Alexandre Zhiboedov for useful discussions. We also thank Simon Caron-Huot, Joan Elias-Miró, and Joao Penedones for discussions and comments on the draft. The work of FA is supported by the Galileo Galilei Institute Boost Fellowship. Research at the Perimeter Institute is supported in part by the Government of Canada through NSERC and by the Province of Ontario through MRI. AG is supported by the European Union — NextGenerationEU, under the programme Seal of Excellence@UNIPD, project acronym CluEs. The work of KH is supported by the Simons Foundation grant 488649 (Simons Collaboration on the Non-perturbative Bootstrap) and by the Swiss National Science Foundation through the project 200020 197160 and through the National Centre of Competence in Research SwissMAP. DK also thanks the organisers and participants of the “S-matrix Bootstrap Workshop V” where part of this work was presented. DK is supported by the SNSF Ambizione grant PZ00P2_193411.
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Acanfora, F., Guerrieri, A., Häring, K. et al. Bounds on scattering of neutral Goldstones. J. High Energ. Phys. 2024, 28 (2024). https://doi.org/10.1007/JHEP03(2024)028
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DOI: https://doi.org/10.1007/JHEP03(2024)028