Speaker
Description
Chiral Belle, put forth in a Snowmass White Paper*, involves a modest upgrade to the SuperKEKB e+e- collider at KEK to enable the existing Belle II detector to explore topics in precision electroweak physics with longitudinally polarized electrons. Spin-dependent observables provide unique, powerful alternative probes for entirely new discovery windows to address exciting hints of physics beyond the standard model. Chiral Belle needs spin rotator units on both sides of the Belle II interaction region to rotate the spin to longitudinal and then return it to its stable arc orientation. For this we use a novel compact, spin rotator concept that preserves the SuperKEKB geometry unchanged.
New multifunction superconducting units replace 4 existing normal-conducting arc dipole bends, but now with solenoids overlaid to rotate spin. Additional skew quadrupoles locally compensate the solenoid’s beam coupling. Careful tuning ensures unchanged optics, tune etc. in the rest of the ring. With the solenoid and skew quadrupole coils off we default back to standard operation.
BNL Direct Wind technology that effectively 3D prints superconductor is used. The spin rotators (far from cryogenics in a warm ring) are housed in compact cryostats with local cryocoolers. We leverage BNL experience making the AGS Snake and other similar projects. To confidently deliver spin units in time for the next SuperKEKB long shutdown, we plan to manufacture and test a quarter length demonstration prototype unit.
Footnotes
- https://doi.org/10.48550/arXiv.2205.12847
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