First observations of beam losses due to bound-free pair production in a heavy-ion collider

TL;DR

This paper reports the first experimental observation of beam losses caused by bound-free pair production in a heavy-ion collider, confirming theoretical predictions and highlighting potential limitations for future collider operations.

Contribution

First experimental detection of bound-free pair production-induced beam losses in a heavy-ion collider, validating theoretical cross sections and informing collider design considerations.

Findings

Observed beam losses due to bound-free pair production at RHIC.

Confirmed theoretical cross section estimates for the process.

Demonstrated potential impact on collider magnet safety at LHC.

Abstract

We report the first observations of beam losses due to bound-free pair production at the interaction point of a heavy-ion collider. This process is expected to be a major luminosity limit for the Large Hadron Collider (LHC) when it operates with 208Pb82+ ions because the localized energy deposition by the lost ions may quench superconducting magnet coils. Measurements were performed at the Relativistic Heavy Ion Collider (RHIC) during operation with 100 GeV/nucleon 63Cu29+ ions. At RHIC, the rate, energy and magnetic field are low enough so that magnet quenching is not an issue. The hadronic showers produced when the single-electron ions struck the RHIC beampipe were observed using an array of photodiodes. The measurement confirms the order of magnitude of the theoretical cross section previously calculated by others.