Residual polarization loss of protons accelerated with Siberian snakes
In plain words
Even with special magnets that flip the spin each turn, protons accelerated to hundreds of GeV lose part of their polarization, for reasons not fully modeled.
Precise statement
RHIC accelerates polarized protons to $255\,\mathrm{GeV}$ with two full Siberian snakes, losing part of the injected polarization during acceleration through intrinsic and imperfection spin resonances. Determine the mechanism of the residual loss (higher-order snake resonances, overlap of intrinsic and imperfection resonances, spin-tune spread) and predict whether $N_s$ snakes preserve more than $70\,\mathrm{percent}$ polarization up to $275\,\mathrm{GeV}$ in an electron-ion collider hadron ring.
What would settle it
Spin tracking that reproduces measured RHIC polarization versus energy and is then applied to the target lattice.