Speaker
Description
In most Dark Matter (DM) models, the DM particles interact with each other through an unknown force carrier, the dark Z_D boson, which is associated with a broken hidden U(1)_D gauge symmetry. The DM particles can communicate to the visible sector only when Z_D develops a tiny coupling to the electromagnetic current due to a small kinetic mixing between the SM hypercharge and Z_D field strength tensors. If Z_D is the lightest particle in the hidden sector, the decay of Z_D is
restricted only to the SM sector. In such a scenario, the production rate is governed by the mass of Z_D and the tiny kinetic mixing parameter ε. Current experiments have put strong bounds on the m_Z_D − ε space for low Z_D mass. However, the limits become weaker as the Z_D becomes heavy, and at the TeV scale, even the projected sensitivities from HL-LHC and FCC-hh deteriorate rapidly, with their reach
limited to m_Z_D ≃ 3 TeV for ε = 0.1.
In this talk, I will discuss the sensitivity reach of multi-TeV muon colliders for a heavy Z_D through the annihilation channel µ+µ− → Z_Dγ. I will demonstrate that muon colliders operating at 3, 6, and 10 TeV with integrated luminosities of 1, 4, and 10 ab−1, respectively, can significantly improve
sensitivity to the kinetic mixing parameter ε over a broad Z_D mass range - particularly above 1 TeV - compared to hadron colliders.
