Indirect Probe of Electroweak-Interacting Particles at Future Lepton Colliders

TL;DR

Future lepton colliders can indirectly detect electroweak-interacting particles and probe higher-dimensional operators through high-precision measurements, even below direct production thresholds, enabling exploration of new physics beyond the Standard Model.

Contribution

This paper estimates the sensitivity of future lepton colliders to electroweak-interacting particles and higher-dimensional operators via quantum effects in precision measurements.

Findings

Particles with masses 100-1000 GeV above beam energy are detectable.

Collider measurements can probe cutoff scales up to tens of TeV.

Quantum effects enable indirect detection below production thresholds.

Abstract

Various types of electroweak-interacting particles, which have non-trivial charges under the $\mathrm{SU}(2)_L \times \mathrm{U}(1)_Y$ gauge symmetry, appear in various extensions of the Standard Model. These particles are good targets of future lepton colliders, such as the International Linear Collider (ILC), the Compact LInear Collider (CLIC) and the Future Circular Collider of electrons and positrons (FCC-ee). An advantage of the experiments is that, even if their beam energies are below the threshold of the production of the new particles, quantum effects of the particles can be detected through high precision measurements. We estimate the capability of future lepton colliders to probe electroweak-interacting particles through the quantum effects, with particular focus on the wino, the Higgsino and the so-called minimal dark matters, and found that a particle whose mass is greater than the beam energy by 100-1000 GeV is detectable by measuring di-fermion production cross sections with $O(0.1)$\% accuracy. In addition, with the use of the same analysis, we also discuss the sensitivity of the future colliders to model independent higher dimensional operators, and found that the cutoff scales corresponding to the operators can be probed up to a few ten TeV.