Optical stochastic cooling of hadron beams at collider energies
In plain words
Optical stochastic cooling, first shown with electrons in a small ring, uses light pulses emitted by each particle to correct that particle's motion; it is unproven for heavy high-energy beams.
Precise statement
Optical stochastic cooling was demonstrated with $100\,\mathrm{MeV}$ electrons at the Fermilab IOTA ring (published 2022) using undulator light at $\sim 1e-4\,\mathrm{cm}$ wavelength without optical amplification. Determine whether OSC with optical amplification can cool protons at $100\,\mathrm{GeV} \text{ to } 7\,\mathrm{TeV}$ with damping time shorter than the intrabeam-scattering time, given undulator radiation per proton, amplifier gain and bandwidth, and path-length stability of $\sim 0.1$ wavelength.
What would settle it
A design calculation with realistic amplifier and lattice parameters giving the damping time, followed by a demonstration with hadrons.