Unitarity bounds on the massive spin-2 particle explanation of muon anomaly

Da Huang; Chao-Qiang Geng; Jiajun Wu

doi:10.1140/epjc/s10052-024-12569-0

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2024) 84: 246
https://doi.org/10.1140/epjc/s10052-024-12569-0

Regular Article - Theoretical Physics

Unitarity bounds on the massive spin-2 particle explanation of muon $g - 2$ anomaly

Da Huang¹^,2^,3^a, Chao-Qiang Geng²^,3 and Jiajun Wu²^,3^,4

¹ National Astronomical Observatories, Chinese Academy of Sciences, 100012, Beijing, China
² School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, UCAS, 310024, Hangzhou, China
³ International Centre for Theoretical Physics Asia-Pacific, Beijing/Hangzhou, China
⁴ CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100190, Beijing, China

^a dahuang@bao.ac.cn

Received: 8 June 2023
Accepted: 18 February 2024
Published online: 8 March 2024

Abstract

Motivated by the long-standing discrepancy between the Standard Model prediction and the experimental measurement of the muon magnetic dipole moment, we have recently proposed to interpret this muon $g - 2$ $$g-2$$ anomaly in terms of the loop effect induced by a new massive spin-2 field G. In the present paper, we investigate the unitarity bounds on this scenario. We calculate the s-wave projected amplitudes for two-body elastic scatterings of charged leptons and photons mediated by G at high energies for all possible initial and final helicity states. By imposing the condition of the perturbative unitarity, we obtain the analytic constraints on the charged-lepton-G and photon-G couplings. We then apply our results to constrain the parameter space relevant to the explanation of the muon $g - 2$ $$g-2$$ anomaly.

© The Author(s) 2024

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