HEFT approach to investigate the muon g-2 anomaly at a muon collider

TL;DR

This paper explores how a multi-TeV muon collider could test new physics explanations for the muon g-2 anomaly by analyzing high-energy processes using HEFT and SMEFT frameworks, highlighting potential increased sensitivity.

Contribution

It compares HEFT and SMEFT approaches to high-energy muon collider processes, assessing their effectiveness in probing new physics related to muon g-2.

Findings

HEFT may offer higher sensitivity to NP in muon g-2

Current HEFT parameters are insufficient for definitive conclusions

Complementary measurements are necessary for better constraints

Abstract

In a previous work \cite{Buttazzo:2020ibd}, it has been pointed out that heavy new physics (NP) contributions to lepton dipole moments and high-energy cross-sections of lepton pairs into Higgs and $\gamma/Z$ bosons are connected, if the electroweak symmetry breaking is realized linearly. As a consequence, a multi-TeV muon collider would provide a unique test of NP in the muon $g$-2 through the study of high-energy processes such as $\mu^+ \mu^-\to h +\gamma /Z$. Since the analysis involved a SMEFT approach to Higgs-processes, it could also be studied by the more general HEFT formulation. We compute the modification of the high-energy cross-section $\mu^+ \mu^-\to h +\gamma/Z$ and $h\to \mu^{+} \mu^{-} +\gamma /Z$ decay using the dimension six HEFT Lagrangian and compare them with the SMEFT analysis. We find that, within the current HEFT analysis, there are plausible scenarios where the HEFT approach could lead to a higher sensitivity to test the NP contributions in the muon $g$-2. However, a more precise knowledge of the new HEFT parameters is needed for a definite conclusion, which motivates the search for complementary measurements.