1. A new measurement of the electron’s electric dipole moment using YbF molecules Mike Tarbutt Centre for Cold Matter, Imperial College London. International Symposium on Molecular Spectroscopy, 23 rd June 2011

2. Motivation 10 -24 10 -22 10 -26 10 -28 10 -30 10 -32 10 -34 10 -36 Multi Higgs Left - Right MSSM  ~ 1 MSSM  ~  Standard Model Predicted values for the electron edm d e (e.cm) The electron’s electric dipole moment (EDM) is sensitive to new physics

3. Measuring the EDM – spin precession Electron precessing in a magnetic field Electron precessing in parallel magnetic and electric fields Electron precessing in anti-parallel magnetic and electric fields Measure change in precession rate when electric field direction is reversed We use the valence electron in the YbF molecule Effective electric field >> Applied electric field

4. Ground state YbF -d e E eff d e E eff X 2  + ( = 0, N = 0) +10 F = 1 F = 0 170 MHz MFMF Electric Field E We measure the splitting 2d e E eff between the M F = +1 and M F = -1 levels

5. Measurement scheme – a spin interferometer Pulsed YbF beam Pump A-X Q(0) F=1 Probe A-X Q(0) F=0 PMT 3K beam F=1 F=0 rf pulse B HV+ HV-

6. Counts B E E Measuring the edm with the interferometer Signal α cos 2 [  ] = cos 2 [(  B B – d e E eff ) T / ћ]

7. Dataset  6194 measurements of the EDM, each derived from 4096 beam pulses  Each measurement takes 6 minutes

8. F = 0 F = 1 rf E Stark-shifted hyperfine interval F = 0 F = 1 rf E Stark-shifted hyperfine interval rf detuning phase shift: ~100 nrad/Hz Imperfect E-reversal Changes detuning via Stark shift Phase correlated with E-direction Correction to EDM: (5.5 ± 1.5) × 10 -28 e.cm Correcting a systematic error

9. EffectSystematic uncertainty (10 -28 e.cm) Electric field asymmetry1.1 Electric potential asymmetry0.1 Residual RF1 correlation1.0 Geometric phase0.03 Leakage currents0.2 Shield magnetization0.25 Motional magnetic field0.0005 Systematic uncertainties

10. Result 10 -24 10 -22 10 -26 10 -28 10 -30 10 -32 10 -34 10 -36 Multi Higgs Left - Right MSSM  ~ 1 MSSM  ~  Standard Model Predicted values for the electron edm d e (e.cm) | d e | < 10.5 × 10 -28 e.cm (90% confidence) Excluded region (5 × 10 -19 Debye) d e = (-2.4 ± 5.7 stat ± 1.5 syst ) × 10 -28 e.cm Improvements planned to explore this region

11. Joe Smallman Dhiren Kara Jony Hudson Ben Sauer Ed Hinds