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Measuring the electron EDM with Cold Molecules

Measuring the electron EDM with Cold Molecules. E.A. Hinds. Imperial College London. Warwick, 25 May, 2006. point electron. +. +. +. +. polarisable vacuum with increasingly rich structure at shorter distances:. How the electron gets structure. -.

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Measuring the electron EDM with Cold Molecules

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  1. Measuring the electron EDM with Cold Molecules E.A. Hinds Imperial College London Warwick, 25 May, 2006

  2. point electron + + + + polarisable vacuum with increasingly rich structure at shorter distances: • How the electron gets structure - (anti)leptons, (anti)quarks, Higgs (standard model) beyond that: supersymmetric particles ………?

  3. Electric dipole moment (EDM) electron T + - edm spin + - beyond std model: If the electron has an EDM, nature has chosen one of these, breaking T symmetry.

  4. 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 (Q: is there a unified theory of all particle interactions?) EDM violates T symmetry Deeply connected to CP violation and the matter-antimatter asymmetry of the universe (Q: why is there more matter than antimatter?)

  5. eEDM (e.cm) Excluded region (Tl atomic beam) Commins (2002) MSSM f ~ 1 Multi Higgs de < 1.6 x 10-27 e.cm Left -Right Our experiment (YbF molecules) is starting to explore this region MSSM f ~ a/p Standard Model 10-22 10-24 10-26 10-28 10-30 10-32 10-34 10-36

  6. CP from particles to atoms (main connections) atom/molecule level nuclear level nucleon level electron/quark level field theory CP model de Tl, YbF Higgs SUSY Left/Right dq dcq neutron Schiff moment NNNN mercury Strong CP qGG ~

  7. g selectron de ~ (loop) sinCP e e gaugino scale of SUSY breaking naturally ~200 GeV SUSY electron edm ~ 5  1025 cm naturally CP phase from soft breaking naturally O(1) me L 2 Theoretical consequences of electron EDM de < 1.6 x 10-27 e.cm - a direct window onto new physics naturally ~ a/p The “natural” SUSY EDM is too big by 300 L> 4 TeV?? CP< 310-3 ??

  8. Suppose de = 5 x 10-28 e.cm (just below current limit) ~ In a field of 100kV/cm de.E _ 10-8 Hz When does mB.B equal this ? ~ B _ 10-18 T ! It seems impossible to control B at this level especially when applying a large E field The magnetic moment problem

  9. amplification de E Interaction energy -deE• electric field FP Polarization factor Structure-dependent relativistic factor ~ 10 (Z/80)3 GV/cm atom or molecule containing electron A clever solution For more details, see E. A. H. Physica Scripta T70, 34 (1997) (Sandars)

  10. Our experiment uses a molecule – YbF 18 GV/cm Amplification in YbF • EDM interaction energy is a million times larger (10-2 Hz) • mHz energy now “only” requires pT stray field control • Insensitive to B perpendicular to E (suppressed by 1010) • Hence insensitive to motional B (vxE/c2=104 pT)

  11. The lowest two levels of YbF +dehE E - - + + -dehE X2S+ (N = 0,v = 0) | -1 > | +1 > F=1 170 MHz | 0 > F=0 Goal: measure the splitting 2dehE to ~1mHz

  12. | +1 | -1  0 | 0  E B |+1 0 ? Source | -1 Split Recombine Probe Pump A-X Q(0) F=1 170 MHz p pulse 170 MHz p pulse A-X Q(0) F=1 Phase difference = 2 (mB + dehE)T/h Interferometer to measure 2dehE

  13. Yb Target Pulsed YbF beam Skimmer The YbF gas pulses are cold (3K), but move rapidly (600 m/s) Pulsed Valve 2% SF6 in 4 bar Ar YAG laser (25mJ, 10ns) How we make the YbF beam A pulsed supersonic jet source

  14. The whole experiment | +1 | -1  | 0  PMT Scanning the rf-frequency Scanning the B-field Probe A-X Q(0) F=1 Time-of-flight profile Fluorescence rf frequency (MHz) Time of flight (ms) B (nT) rf recombine rf split Pulsed YbF beam Pump A-X Q(0) F=1

  15. Fit to YbF interferometer fringes 40 30 20 10 0 0 -60 -30 30 60 Phase difference = 2(mB+dehE)T/h Interference signal (kpps) Magnetic field B (nT)

  16. fringe pattern versus time of flight arrival time (ms) narrower fringes experimental data 2.7 2.6 slower molecules 2.5 faster molecules 2.4 -200 -100 0 100 200 2.3 Magnetic field B (nT)

  17. E -E df = 4dehET/h - 4dehET/h Detector count rate -B0 B0 Applied magnetic field Measuring the edm

  18. EDM data taken 100 hrs at 13 kV/cm 3 2 1 -1 -2 -3 80 hrs at 20 kV/cm 3 2 1 -1 -2 -3 de (10-25 e.cm)

  19. EDM Data summary • Each dataset has a statistical sensitivity to de of 7 x 10-28 e.cm • No result yet - the experiment is incomplete • In particular, measurements of systematic effects

  20. Systematic tests • 16 internal machine states – linear combinations flag undesirable asymmetries  • 4 external machine states  • Simultaneous measurement of magnetic fields inside the machine  • Simultaneous measurement of leakage currents  • Measurements at low electric field in progress • Battery runs etc, etc in progress • Repeat using a control molecule in preparation

  21. Sensitivity level: 2 x 10-28 e.cm Sensitivity level: ~10-29 e.cm Upgrades in progress

  22. Deceleration and trapping • We are building a Stark decelerator for YbF and CaF molecules • Aim to bring molecules to rest and load them into a trap • Perform the edm experiment with slow, trapped molecules: coherence times > 100ms

  23. The eEDM roadmap

  24. Principle of deceleration (1,0) (0,0) For a review see arXiv:physics/0604020 Apr 2006

  25. Our alternating gradient decelerator design 21 stages macor insulators high voltage electrodes

  26. Optical guiding Ion Trapping AG focussing in other contexts

  27. First YbF decelerator result Decelerator on Decelerator off Signal 1.3 1.4 1.5 1.6 1.7 1.8 Time of flight (ms) Phys. Rev. Lett. 92, 173002 (2004)

  28. Now also CaF

  29. trap t ~ 1s E B supersonic source decelerator recombine probe prepare split interferometer Vision of experiment with trapped molecules

  30. Cs atoms Fountain (LBL), Trapped (Penn State), Trapped (Texas) Long coherence time Gadolinium Garnets GGG (LANL), GIG (Amherst) Huge number of electrons Molecules Large effective E field Metastable PbO in cell (Yale) Trapped PbF (Oklahoma) Large effective E field & long coherence time Trapped HBr+ ions (JILA) Other electron EDM searches

  31. Neutron EDM expt Hg atom co-magnetometer laser beam polarised neutrons in a bottle Electric field 10kV/cm New limit: 3.0 x 10-26e. cm hep-ex/0602020 Room-temperature experiment finished Measurement: dnxE spin precession

  32. CryoEDM starts in October polarised neutrons moderated in superfluid helium Ultimately 100x more sensitive Several other neutron EDM experiments also starting

  33. neutron: d e.cm d(muon) 7×10-19 Electro- 10-20 magnetic electron: 10-22 d(proton) 6×10-23 YbF expt 10-24 d(neutron)  3×10-26 Multi SUSY Higgs d(electron) 1.6×10-27 f ~ 1 10-28 f ~ a/p Left-Right 10-29 trapped molecules 1960 1970 1980 1990 2010 2020 2030 2000 Current status of EDMs

  34. Measuring the electron EDM has great potential to elucidate • particle physics beyond the standard model • CP violation • matter/antimatter asymmetry of the universe Conclusion Some of the most fundamental questions in physics

  35. Current Group Members Collaborators Richard Darnley Henry Ashworth Ed Hinds Manu Kerrinckx Jony Hudson Mike Tarbutt Ben Sauer Antoine Weis Rick Bethlem Gerard Meijer

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