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. Based on CRESST-II and EDELWEISS-II expertise, with additional groups joining Baseline targets: Ge, CaWO 4 (A dependence) Mass: above 100 kg Timescale: continue CRESST-II and EDELWEISS-II Started 17 March 2005 EURECA R&D = demonstrate CRESST/EDELWEISS European Underground Rare Event Calorimeter Array

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

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

5. C particleantiparticle(Q→−Q) P positioninverted(r →−r) T timereversed (t→−t) Fundamental Inversions

6. Symmetries Weak interactions are not symmetric under P or C Normal matter - n, ,  - 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 spin (P no big deal)(CP big deal) +−+− −+−+ P +−+− −+−+ T P odd T odd (assuming CPT invariance) neutron EDM:

8. Overview SM contribution is immeasurably small, but... most models beyond SM predict values about 10 6 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 is effectively zero in standard model but big enough to measure in non-standard models Direct test of physics beyond the standard model EDM violates T symmetry Deeply connected to CP violation and the matter-antimatter asymmetry of the Universe

10. A Bit of History Experimental Limit on d (e.cm) 1960197019801990 neutron: electron: 2000 10 -20 10 -30 10 -22 10 -24 10 -26 10 -28  Left-Right 10 -32 10 -20 10 -22 10 -24 10 -30 Multi Higgs SUSY  Standard Model Electro- magnetic 10 -34 10 -36 10 -38

11. d n makes precession faster...... or slower. Measurement Principle BE BB Measure Larmor spin precession frequency in parallel & antiparallel B and E fields:

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

13. The Neutron Mirror >> interatomic spacing; neutrons see Fermi potential V F Critical velocity for reflection: ½mv c 2 = V F UCN: v  6 m/s: total internal reflection possible. n n n s s B v c depends on orientation of neutron spin, so can polarise by transmission.

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

15. Ramsey Resonance Phase gives frequency offset from resonance.

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

17. The Measurement

18. Mercury Magnetometry PMT Polarized mercury atoms

19. With Magnetometer

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

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

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

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

24. The Cryogenic Setup

25. The Ramsey Cell

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

27. Improvements on Statistics Polarisation+detection  = 0.75x 1.5 Electric field: E = 10 6 V/mx 2.0 Precession period: T = 130 sx 1.8 Neutrons counted: N = 6 x 10 6 /dayx 14.9 (with new beamline) x 2.6 Item RT Expt Increase Total improvement = x80 (x200)

28. Superconducting Shield

29. SQUIDS from CRESST SQUIDs for Magnetometry

30. Motivation: no contact resistance

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

32. Reality Check xx -e +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.