New Insights into Spin Coherence Time

1. Based on • Lehrach (FZJ), B. Lorentz (FZJ), W. Morse (BNL), • N.Nikolaev(Landau Inst) & F. Rathmann (FZJ) • & EDM COSY Workshops • & EDM-BNL & JEDI Teleconferences • More from • Ed Stephenson, Greta Guidoboni, YannisSemertzidis, • YuriiOrlov, Frank Rathmann, Alfredo Luccia • andothersatthis Workshop New Insights into Spin Coherence Time EDM, ECT*, Trento, 2 October 2012

2. Layout: • Why the EDM and at which accuracy? • TF-BMT equation and EDM signal with frozen horizontal (longitudinal) spin • The alternative and precursor: EDM signal from idly precessing horizontal spin at all magnetic COSY with RF E-fields • Spin tune with momentum spread and Spin Coherence Time • RFE(B)-flipper: shall a new element in a ring destroy spin coherence? • Spin Decoherence-free magic energies and flattop RFE flipper • Semertzidis & Orlov (and NNN & Silenko)EDM-transparent Wien filter is equivalent to the MDM-transparent RFE flipper • Betatron Oscillations, Path Lengthening, Spin Tune Chromaticity and all that: ad to Greta Guidoboni‘s talk (also recall Novosibirsk -1987) • dEDM and pEDM can for the first time be constrained at COSY reaching the ballpark of modern theory predictions

3. Future: Search for Electric Dipole Moments Electric dipole moment (EDM) A permanent EDM of a fundamental particle violates both parity (P) and time reversal symmetry (T). Assuming CPT to hold, the combined symmetry CP is violated as well. Frank Rathmann 19th International Spin Physics Symposium 3

4. Importance of Spin Coherence Timefor EDM Searches • Lehrach (FZJ), B. Lorentz (FZJ), • W.Morse (BNL), • N.Nikolaev (FZJ & Landau Inst) • F.Rathmann (FZJ) RWTH / IKP FZJ, 3 May 2012

5. Upper bounds on the neutron EDM

6. PNPI-ILL-PTI collaboration (Serebrov et al) Prospects to increase sensitivity of EDM measurements Gatchina EDM spectrometer at ILL Gatchina EDM spectrometer 1975

8. Future: Search for Electric Dipole Moments NEW: EDM search in time development of spin in a storage ring: “Freeze“ horizontal spin precession; watch for development of a vertical component ! A magic storage ring for protons (electrostatic), deuterons, … One machine with r~30 m 8

9. Polarized beam in all magnetic ring makes one turn ring A one particle with magnetic moment “spin closed orbit vector” “spin tune” Vertical stable polarization vs. idle precession of the horizontal one with the momentum dependent spin tune 9

10. Spin coherence We usually don‘t worry about coherence of spins along the rotation axis Polarization not affected! At injection all spin vectors aligned (coherent) After some time, spin vectors get out of phase and fully populate the cone Situation very different, when you deal with  Longitudinal polarization vanishes! In an EDM machine with frozen spin, observation time is limited. At injection all spin vectors aligned After some time, the spin vectors are all out of phase and in the horizontal plane Spin coherence time: 103 s for measurement on 10-29 e·cm level

14. Extreme cases of phase slips: • Random effects in the momentum spread give finite SCT • Regular synchrotron oscillations do not decohere horizontal spin: infinite SCT? • Rectangular (flat-top) excitation of a flipper suppresses dangerous flipper phase slip effects (A. Lehrach et al. 2011): to be tested at COSY • Spin tune and flipper phase slips are of the same origin  cancellations at magic energies and flipper harmonics, to be tested at COSY (A. Lehrach et al. 2011) • Runaway decoherence from the path lengthening by betatron oscillations (Ed Stephenson et al. 2012: Successfully learning to tame them at COSY. Also derive lessons from Novosibirsk-1987) • New development at COSY: fast time stamp in the polarimetry of rapidly precessing horizontal spin

17. Spin Coherence Timewith RFE Flipper • Possibility to increase spin coherence time by 3 to 5 orders of magnitude • Experiment with polarized COSY beam soon

19. Why EDM-transparent Wien-Filter? • The motional E-field in a ring proper rotates EDM but with a constant amplitude • MDM-transparent RFE filter  Lorentz force & unwanted excitation of coherent betarton oscillations and perhaps a runaway decoherence • Wien filter eliminates the E-field on EDM • 2012: Y. Semertzidis & Yu. Orlov (also NNN and A.Silenko): EDM-transparent Wien-filter in a COSY ring still generates the EDM signal • The reason: Wien-filter is MDM-nontrasparent and gives rise to a frequency modulation of the spin tune which conspires with the motional E-field in a ring. The EDM signal is the same as for MDM-transparent flipper • The spin decoherence properties of the two devices are the same • Run the radial RFB flipper in the Wien-filter mode

23. Spin Dynamics for EDMat COSY • Lehrach (FZJ), B. Lorentz (FZJ, • W.Morse (BNL), • N.Nikolaev (FZJ & Landau Inst) • F.Rathmann (FZJ) PNPI Winter School, Rajvola, 01.02. 2012

24. Path lengthening & spin tune spread  runaway decoherence • Greta Guidoboni, COSY expt on idle precession: taming spin tune spread by sextupole magnets • Find ways to randomize the betatron oscillation amplitude of individual particles • Future expts at COSY: How will tampering the chromaticity work with running RFE flipper?

25. Outlook • Much progress in understanding SCT at COSY • Suppression of spin decoherence from longitudinal momentum spread at special (magic) energies • Taming spin tune spread effects by fine tuning the chromaticity by sextupoles • Away from runaway spin decoherence by randomizing the spin tune spread • COSY constraints on pEDM & dEDM can reach the ballpark of theoretical expectations

26. Backup: