CryoEDM – A Cryogenic Neutron-EDM Experiment Collaboration:

1. CryoEDM – A Cryogenic Neutron-EDM Experiment Collaboration: Sussex University, RAL, ILL, Kure University, Oxford University Hans Kraus … but before: some advertising for EURECA

2. European Underground Rare Event Calorimeter Array • Based on CRESST-II and EDELWEISS-II expertise, with additional groups joining • Baseline targets: Ge, CaWO4 (A dependence) • Mass: above 100 kg • Timescale: continue CRESST-II and EDELWEISS-II • Started 17 March 2005 • EURECA R&D = demonstrate CRESST/EDELWEISS

3. EURECA Collaboration CRESST + EDELWEISS + new forces • France • CEA/DAPNIA Saclay • CEA/DRECAM Saclay • CNRS/CRTBT Grenoble • CNRS/CSNSM Orsay • CNRS/IPNL Lyon • CNRS/IAP Paris • CERN • England • Oxford (H Kraus, coordinator) • Germany • Max-Planck Institut f. Physik, Munich • Technische Universität München • Universität Tübingen • Karlsruhe Universität • Forschungszentrum Karlsruhe

4. Back to nEDMOverview • Why EDM? - Theoretical Background • The Method of Ramsey Resonance • Room-temperature Experiment • Ultra-Cold Neutrons • The Cryogenic Experiment

5. Fundamental Inversions Cparticle antiparticle (Q→−Q) Pposition inverted (r→−r) Ttime reversed (t→−t)

6. Symmetries Weak interactions are not symmetric under P or C Normal matter - n, m, p - readily breaks C and P symmetry. The combination CP is different Normal matter respects CP symmetry to a very high degree. Time reversal T is equivalent to CP (CPT theorem) Normal matter respects T symmetry to a very high degree.

7. EDM breaks P and T Symmetry P T +− +− −+ (P no big deal) −+ (CP big deal) neutron EDM: spin P odd T odd (assuming CPT invariance)

8. Overview • SM contribution is immeasurably small, but... • most models beyond SM predict values about 106 greater than SM. Very low background! • EDM measurements already constrained SUSY models. • “Strong CP Problem”: Why does QCD not violate CP? Nobody knows. • Finally, there is the question of baryon – anti- baryon asymmetry in the universe.

9. Two Motivations to Measure EDM EDM violates T symmetry Deeply connected to CP violation and the matter-antimatter asymmetry of the Universe EDM is effectively zero in standard model but big enough to measure in non-standard models Direct test of physics beyond the standard model

10. A Bit of History neutron: 10-20 electron: 10-22 10-24 Experimental Limit on d (e.cm) 10-26 10-28 10-30 1960 1970 1980 1990 2000 Electro- 10-20 magnetic 10-22 10-24 SUSY Multi Higgs f ~ 1 Left-Right 10-30 f ~ a/p 10-32 10-34 Standard Model 10-36 10-38

11. Measurement Principle Measure Larmor spin precession frequency in parallel & antiparallel B and E fields: B E dn makes precession faster... ... or slower. mB

12. Measurement Principle Apply constant magnetic field, alternate electric field: Measure difference in precession frequency and find Electric Dipole Moment

13. The Neutron Mirror B n s n s n >>interatomic spacing; neutrons see Fermi potential VF Critical velocity for reflection: ½mvc2 = VF UCN: v 6 m/s: total internal reflection possible. vc depends on orientation of neutron spin, so can polarise by transmission.

14. Ramsey’s Technique “Spin up” neutron... 1. Apply /2 spin flip pulse... 2. Free precession... 3. Second /2 spin flip pulse. 4.

15. Ramsey Resonance Phase gives frequency offset from resonance.

16. The Room Temperature Experiment High voltage lead Four-layer mu-metal shield Coil for 10 mG magnetic field Quartz insulating cylinder Upper electrode Main storage cell Hg u.v. lamp PMT to detect Hg u.v. light Vacuum wall Mercury prepolarising cell RF coil to flip spins Hg u.v. lamp Magnet S N UCN guide changeover UCN polarising foil Ultracold neutrons (UCN) UCN detector

17. The Measurement

18. Mercury Magnetometry Polarized mercury atoms PMT

19. With Magnetometer

20. False EDM Signals Different for 199Hg and neutrons see: Phys. Rev. A 70, 032102 (2004) Need for precise magnetometry

21. Room Temperature Results E = 4.5 kV/cm B = 1mT Tcoherence~ 130s Hg co-magnetometer (B measured to 1 pT rms) Neutron edm result: Phys. Rev. Lett. 82,904 (1999) |dn|< 6.310-26e cm

22. Ultra-cold Neutron Production phonon cold neutron ultra-cold neutron λn = 8.9Å; E = 1.03meV 1.03 meV (11K) neutrons down-scatter by emission of phonons in superfluid helium at 0.5K Up-scattering suppressed: hardly any 11K phonons

23. Ultra-cold Neutron Production phonon cold neutron ultra-cold neutron 0.91±0.13 UCN cm−3 s−1 observed C A Baker et al., Phys. Lett. A 308 (2002) 67

24. The Cryogenic Setup

25. The Ramsey Cell

26. Ultra-cold Neutron Detection • ORTEC ULTRA at 430mK temperature. • Equipped with thin surface layer of 6Li. • Using:n + 6Li → α + 3H 2.73MeV triton-peak α-peak in noise

27. Improvements on Statistics Item RT Expt Increase • Polarisation+detection = 0.75 x 1.5 • Electric field:E = 106 V/m x 2.0 • Precession period:T = 130 s x 1.8 • Neutrons counted:N = 6 x 106 /day x 14.9 (with new beamline)x 2.6 Total improvement = x80 (x200)

28. Superconducting Shield

29. SQUIDS from CRESST SQUIDs for Magnetometry

30. Motivation: no contact resistance

31. Magnetometry Tests Pickup Loop SQUIDs SQUID 4 SQUID 5 4 5 SQUID 4 + SQUID 5 Resolution 0.16 pT (1.6nG) @ 1Hz

32. Reality Check +e Dx -e If neutrons were the size of the Earth … … then current EDM limit means charge separation of Δx ≈ 3μm

33. Summary • After half a century, no sign of an EDM … • SUSY being squeezed. Ever-tighter limits continue to constrain physics beyond SM. • Room-temperature experiment finished. • CryoEDM: under construction with aim of ~100 improvement in sensitivity.