HECATE

Marcin Chrząszcz,Marco Drewes,Jan Hajer

doi:10.1140/epjc/s10052-021-09253-y

Abstract

The next generation of circular high energy collider is expected to be a lepton collider, FCC-ee at CERN or CEPC in China. However, the civil engineering concepts foresee to equip these colliders with bigger detector caverns than one would need for a lepton collider, so that they can be used for a hadron collider that may be installed in the same tunnel without further civil engineering. This opens up the possibility to install extra instrumentation at the cavern walls to search for new long-lived particles at the lepton collider. We use the example of heavy neutral leptons to show that such an installation could improve the sensitivity to the squared mixing parameter by almost half an order of magnitude.

Highlights

Future lepton colliders such as the FCC-ee [1] or CEPC [2] have an extremely rich physics program [3,4]
In this Letter we point out that an instrumentation of the large detector caverns that are planned at future circular lepton colliders could considerably increase the sensitivity of searches for long-lived particles (LLPs)
The main difference between the HErmetic CAvern TrackEr (HECATE) concept and other proposals lies in the approximate 4π solid angle coverage that can be achieved by covering the cavern walls with detectors

Summary

Introduction

Future lepton colliders such as the FCC-ee [1] or CEPC [2] have an extremely rich physics program [3,4] They are outstanding intensity frontier machines that can study the properties of the electroweak and Higgs sector at unprecedented accuracy, but they can search for feebly coupled hidden particles that have escaped detection at the LHC due to their low production cross section. Due to their small interaction strength hidden particles can have comparably long lifetimes. We propose to include such a HErmetic CAvern TrackEr (HECATE) in future FCC-ee and CEPC studies.

Possible implementation and cost estimate

Sensitivity estimate

Discussion and conclusions