Search for an Electric Dipole Moment of 199 Hg

1. Search for an Electric Dipole Moment of 199Hg BlayneHeckel University of Washington Graduate students: Jennie Chen, Brent Graner Scientific glassblower: Erik Lindahl Support: NSF and DOE Low Energy Nuclear Physics

2. History of 199Hg EDM results Lamoreaux Jacobs Klipstein Fortson Griffith Swallows Romalis Loftus Fortson Current sensitivity 1987 1993 1995 2001 2014 2009

3. 4-Cell, 199Hg Magnetometer EDM sensitive frequency combination E wOT Cancels up to 2nd order gradient noise wMT E B wMB wOB EDM insensitive channels: ωOT - ωOB and (ωOT + ωOB) – (ωMT + ωMB) monitor for E field correlations odd and even in z, respectively.

5. Cell Holding Vessel Cell Holding Vessel

6. Schematic Overview

7. Vapor Cells Pump Probe

8. Improvements to the EDM Experiment • Vapor Cell development: • Stablespin lifetimes of 800, 600, 500, and 270 sec • Problem of disappearance of Hg within the cells solved • Reduced magnetic field noise – less conducting materials near the cells • Light induced noise and systematic effects eliminated by precession in the dark • Reduced high voltage leakage currents: • Measure separately the currents across the cell and to the ground plane • Commercial uv laser provides better stability • We are working on improving the beam pointing stability

9. Precession in the dark Optical rotation angle of 240 A B Advantages: Longer spin coherence times Light induced noise and systematic errors eliminated Insensitive to common mode B field drift

10. Frequency difference extraction Because we are only interested in cell pair frequency differences during the light-off period, we need only the phase difference between cells at the end of the A period and start of the B period: We find Δω by multiplying the signals from the 2 cells.

11. Filtered Data 10 Photo-Diode (V) 8 6 4 2 Time (s) 250 100 50 150 200 2.0 ΔωMT-MB (mrad) 1.5 1.0 0.5 0 TA TB

12. System Performance Average angular frequency relative to first scan Rad/s Run Number This corresponds to a drift of ~1 µGauss/day

13. Δω (MT-MB) Middle cell angular frequency difference Rad/s 0.3 nG/day Δω (OT-OB) Outer cell angular frequency difference Rad/s

14. Δω (OT-MT) +Δω (OB-MB) Quadratic field drift channel Rad/s ΔωC EDM sensitive frequency combination Rad/s 80 pG/day

15. One day EDM signal ωedm(n) = (-1)n [ΔωC(n-1) - 2 ΔωC(n) + ΔωC(n+1)]/4 Rad/s ωedm = xx ± 2.0 × 10-9rad/s, a factor of 4 improvement over 2009 (3.5 × 10-29 e-cm/day for 10kV runs)

16. Data Sequences • EDM data is taken in ``sequences’’. Each sequence comprises: • A defined set of cell orientations and ordering in the vessel • Equal number of day long runs at 6kV and 10kV • Equal number of runs with normal and reversed magnetic fields • Equal number of runs with fast and slow high voltage ramp rates • Typically 16 -20 runs total We have completed 7 data sequences and have 5 to go for a complete EDM data set. For seq. 1-6: at 10kV, dHg = -(13.4 ± 5.6) × 10-30 e-cm at 6kV, dHg = -(15.6 ± 9.3) × 10-30 e-cm combined, dHg = -(14.0 ± 4.8) × 10-30 e-cm (blind offset in place)

17. Sequence 1-6 χ2 = 1.05 ωc(rad/sec)

18. Sequence 1-6 χ2 = 1.02 ωc(rad/sec)

19. 10 kV χ2 = 1.22 EDM data by Sequence ωc × 10-10 rad/s B field up B field down Seq.1 Seq.2 Seq.3 Seq.4 Seq.5 Seq.6 χ2 ω c × 10-10 rad/s Seq.1 Seq.2 Seq.3 Seq.4 Seq.5 Seq.6

20. Systematic Uncertainties 2009 Error Budget -- Scale with frequency precision X (no sparks observed) X (precession in the dark)

21. Leakage Currents We now measure separately the currents flowing down the cell walls and through the dry air. 10 kV IGas= 0.4 pA (2009) 0 Volts ICell= 0.08 pA (2009) 2014: With tin oxide coated ground planes (rather than gold), we see 10 times less leakage current -- no photo-electrons: Igas = 0.04 pA (2014), Icell = ?

22. Issues to address • Better understanding of the long time constants associated with the leakage currents • Identification of the dominant source of excess noise(simulated data with Gaussian photon shot noise added results in 40% smaller EDM values) • Identification of the source for occasional runs with 2-3 sigmacorrelations between the outer cell frequency difference and high voltage

23. Summary • We anticipate a 199Hg EDM result with a factor of roughly 4 improvement in statistical precision by the end of 2014. • The data, so far, looks reasonable but there remains work to do concerning systematic errors. • We are constructing shorter vapor cells to allow us to increase the applied electric field in our current EDM apparatus.

25. Laser System SDL MOPA: 500 mW at 1015 nm 1st Doubler: 130 mW at 507 nm 2nd Doubler: 6 mW at 254 nm

26. Transverse Pumping / Optical Rotation B B wL Pump Phase 254 nm Linear Detector 254 nm s+ Linear Polarizer Probe Phase

27. Transverse Pumping / Optical Rotation Pump Probe Probe Optical Rotation Angle Absorption

28. Typical 24 Hour Run

29. Final Dataset and Statistical Error d(199Hg) = (0.49 ± 1.29stat )x10-29e cm 0.1 nHz (~ 7.5 ppt)

30. Systematic Errors and Tests for Systematic Effects • No Statistically Significant Dependence on: • The Vapor Cells or Electrodes (or their orientation) • The DAQ Channel Ordering • The Vessels 99% of Total Error Systematic Error Budget Statistical Error 12.90

31. Bounds on CP Violating Parameters d(199Hg) = (0.49 ± 1.29stat ± 0.76sys ) x 10-29e cm | d(199Hg) | < 3.1 x 10-29e cm (95% CL) Quark Chromo EDMs Proton EDM Semi-Leptonic Interactions: QCD Phase Neutron EDM Electron EDM Confidence Levels: 199Hg (95%), 205TI (90%), TIF (95%)

32. Current Status Six-fold Reduction of Noise • More uniform and stable magnetic field • Detection of both polarization states of transmitted light • ``In the Dark’’ elimination of uv light induced noise and systematic error Old Analysis ``In the Dark’’

33. Current Status Improved Hg Vapor Cells: so far, natural Hg test cells • Hydroxy bonded rather than glued – should last forever • 600 sec spin lifetime (distilled wax + smaller magnetic field gradients) Remaining Tasks: • Construct enriched Hg vapor cells • Acquire a new uv laser source

34. Summary Our 2009 Result led to a New Limit on the EDM of 199Hg | d(199Hg) | < 3.1 x 10-29e cm (95% CL) • Factor of 7 Reduction in Previous Upper Limit • Improved Bounds on CP Violating Parameters Upgrading the Current Apparatus • Expect Factor of 5 improvement in Experimental Sensitivity • Expect to begin data collection later this year Among his many accomplishments, Norman Ramsey founded the research field of EDM measurements and developed many of the techniques needed to do such precise measurements. He will always be an inspiration to us.

35. Reasons to Expect more T (CP) Violation • The observed matter-antimatter asymmetry: CP violation in the SM is too small to account for Baryogenesis. • The Strong CP problem: Why is QCD so small? • The Standard Model is incomplete:Extensions to the SM, such as SUSY, introduce new phases that lead to new sources of CP violation often 106 times larger than the SM for EDMs.

36. From the 199Hg EDM to Models for CP Violation Semileptonic Interactions: CSCP CT 199Hg Atomic EDM Hyperfine Coupling: d(e) Atomic Physics 199Hg Schiff Moment Contributions to S from p, n EDMs Nuclear Physics CP-Violating Pion-Nucleon Coupling d(p) d(n) QCD CP-Violating QCD Term, Quark Chromo-EDMs SUSY, etc … Naturalness Parameters Model-Dependent CP-Violating Parameters

37. Constrained MSSM

38. Measuring an EDM via Larmor Precession B E d m wL