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Philip Harris University of Sussex (for the EDM Collaboration)

The Neutron EDM Experiments at the ILL. Philip Harris University of Sussex (for the EDM Collaboration). Highlights. New (but preliminary ) limit: |d n | < 3.1 x 10 -26 e.cm. 1. nEDM “Classic”. 2. CryoEDM. Under development: 100x improved sensitivity. d n = d n s.

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Philip Harris University of Sussex (for the EDM Collaboration)

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  1. The Neutron EDM Experiments at the ILL Philip Harris University of Sussex (for the EDM Collaboration)

  2. Highlights New (but preliminary) limit: |dn| < 3.1 x 10-26 e.cm 1. nEDM “Classic” 2. CryoEDM Under development: 100x improved sensitivity

  3. dn = dns Electric Dipole Moments • Separation between+,- charge centres • EDMs are • P odd • T odd • Complementary approachto study of CPv + E

  4. CP violation & the neutron EDM • SM EDM predictions very small... • ... so no SM background to worry about • Beyond SM predictions typ. 106 greater • ... so EDMs are excellent probe of BSM CPv • SM parameterisation of CPv inadequate to explain baryon asymmetry • Strong CP Problem: s < 10-10 rads

  5. g g squark squark q q q q gaugino gaugino quark color dipole moments quark electric dipole moments mq scale of SUSY breaking naturally ~200 GeV CP phase from soft breaking naturally O(1) c dq, dq~ (loop factor)sinCP c du,d, du,d ~ 31024 cm naturally n and Hg experiments give du< 2  1025 dd< 5  1026 ~ 100 times less! c du< 3  1026 L2 2 c dd< 3  1026 Implications for SUSY naturally ~ a/p L> 2 TeV? CP< 10-2 ?

  6. Now CryoEDM History Factor 10 every 8 years on average

  7. Measurement principle Use NMR on ultracold neutrons in B,E fields. () – () = – 4 E d/ h assuming B unchanged when E is reversed. B0 B0 B0 E E <Sz> = + h/2 h(0) h() h() <Sz> = - h/2 Energy resolution of our detector: 10-21 eV

  8. Apparatus HV feedthru Neutron storage chamber B-field coils

  9. Electric Field + - nEDM measurement • Look for n freq changes correlated with changes in E

  10. Mercury co-magnetometer Compensates B drift...

  11. nEDM measurement Raw neutron frequency 29.9295 Corrected frequency 29.9290 29.9285 29.9280 -10 D B = 10 T Precession frequency (Hz) 29.9275 29.9270 29.9265 29.9260 0 5 10 15 20 25 Run duration (hours)

  12. Current limit set here Stat. limit now 1.54 x 10-26 e.cm Neutron EDM results (binned)

  13. Systematics • Consider • Should have value 1 • R is shifted by magnetic field gradients • Plot EDM vs measured R-1:

  14. Systematics Magnetic field down

  15. Systematics Magnetic field up

  16. and, from Special Relativity, extra motion-induced field Geometric phase J.M. Pendlebury et al., PRA 70 032102 (2004) Two effects:

  17. Bnet Br Bnet Bv Bv Bv Bnet Br Bnet Geometric phase ... so particle sees additional rotating field Bottle (top view) Frequency shift  E Looks like an EDM

  18. The answer? B up B down Results EDM R-1 0 Nearly...

  19. Results Small dipole/quadrupole fields can pull lines apart & add GP shifts EDM B up R-1 0 B down

  20. Results Small dipole/quadrupole fields can pull lines apart & add GP shifts EDM B up R-1 0 Measure and apply correction ...difficult! B down

  21. Error budget

  22. PRELIMINARY Results dn = (-0.31  1.54  1.00) x 10-26 e.cm New (preliminary) limit: |dn| < 3.1 x 10-26 e.cm (90% CL) Preprint expected soon

  23. Dispersion curve for free neutrons Landau-Feynman dispersion curve for 4He excitations ln = 8.9 Å; E = 1.03 meV CryoEDM 100-fold improvement in sensitivity! R. Golub and J.M. Pendlebury Phys. Lett. 53A (1975), Phys. Lett. 62A (1977) More neutrons Higher E field Better polarisation Better NMR time

  24. CryoEDM overview Neutron beam input Cryogenic Ramsey chamber Transfer section

  25. Cryogenic Ramsey chamber HV electrode Superfluid He n storage cells

  26. CryoEDM Turns on October 2006

  27. Conclusions • EDM “Classic”: new (preliminary) limit, factor 2 improvement • CryoEDM coming soon – 100x more sensitive • Watch this space!

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