Probing dark particles indirectly at the CEPC

TL;DR

This paper investigates how quantum loop effects of nearly degenerate dark matter candidates and their parent particles can be indirectly probed at the CEPC through muon pair production, using a simplified model with new scalar and fermion fields.

Contribution

It introduces a method to detect dark sector particles via loop effects on muon couplings at the CEPC, extending beyond direct detection capabilities.

Findings

Loop contributions can modify muon couplings significantly.

CEPC measurements could reveal effects of new scalar and fermion particles.

Potential to probe dark sector particles with small mass splittings.

Abstract

When dark matter candidate and its parent particles are nearly degenerate, it would be difficult to probe them at the Large Hadron Collider directly. We propose to explore their quantum loop effects at the CEPC through the golden channel process $e^+e^-\to \mu^+\mu^-$. We use a renormalizable toy model consisting of a new scalar and a fermion to describe new physics beyond the Standard Model. The new scalar and fermion are general multiplets of the $SU(2)_L\times U(1)_Y$ symmetry, and couple to the muon lepton through Yukawa interaction. We calculate their loop contributions to anomalous $\gamma\mu^+\mu^-$ and $Z\mu^+\mu^-$ couplings which can be applied to many new physics models. The prospects of their effects at the CEPC are also examined assuming a 0.002 accuracy in the cross section measurement.