Here, we calculate the effects of astrophysical gravitational waves (GWs) on the travel times of proton bunch test masses in circular particle accelerators. We show that a high-precision proton bunch time-tagging detector could turn a circular particle accelerator facility into a GW observatory sensitive to millihertz GWs. We comment on sources of noise and the technological feasibility of ultrafast single-photon detectors by conducting a case study of the Large Hadron Collider at CERN.

• Received 10 July 2020
• Accepted 30 November 2020

DOI:https://doi.org/10.1103/PhysRevD.102.122006