Speaker
Description
To test $T$- and $P$-violation by proton EDM requires an electric storage ring (SR) with simultaneously counter-circulating, frozen-spin proton beams. The CPEDM feasibility study proposes a low-energy prototype ring with superimposed electric and magnetic bending storing frozen-spin 49.65 MeV (clock-wise) protons and pseudo-frozen spin 24.73 MeV (counter-clockwise) protons; $pd$ combinations are also practical and interesting.
Such a SR in the collider mode can be used to search for beyond Standard Model semi-strong $T$-violation in elastic $pp$ or $pd$ scattering. Suggested by Lee & Wolfenstein, Prentki & Veltman and Okun, as a source of CP-violation, it still awaits the experimentum crucis.
Initial spin states are guaranteed by phase-lock technique developed by JEDI; a comparison of polarization effects in the direct and time-reversed reactions requires matching polarimetry of final-state particles. The notable exception is $T$-violation in collisions of vector polarized protons and tensor polarized deuterons.
Full final state polarimetry stops the scattered particles in azimuthally symmetric full acceptance tracking chambers of the polarimeter, totaling $3\pi$ sr. This high-efficiency polarimetry is feasible only because the scattered particles are soft enough to be stopped in the polarimeter, making collider experiments much superior to fixed target experiments.
Besides a comparison of the analyzing powers to final-state single-particle polarizations, an access to $T$-violation in double-spin observables will be possible. With a $pp$ luminosity of 0.6 mb$^{-1}$s$^{-1}$, producing $10^8$ elastic scatters per year, the time-reversal violation upper limits, currently at the level of a few 1%, could be lowered by more than one order in magnitude.
| Primary frontier topic | Rare Processes and Precision Measurements Frontier |
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