BEAMS
In the literature: open
What sets the much lower beam-beam limit in hadron colliders
In plain words
Hadron colliders tolerate only about a tenth of the beam-beam strength of electron machines because nothing damps their motion. The detailed process by which particles drift out of the beam over hours is not predictable.
Precise statement
Without radiation damping, hadron colliders are limited to total $\xi \sim 0.01\ \text{to}\ 0.03$. Predict the beam lifetime and emittance growth over 1e8 to 1e9 turns from beam-beam nonlinearities combined with tune modulation, power-supply ripple and noise, and determine the scaling of the limit with these noise sources.
What would settle it
Long-term diffusion predictions matching measured emittance growth and losses in the LHC or RHIC under controlled noise injection.