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A Search for Temporal and Gravitational Variation of a in Atomic Dysprosium

A Search for Temporal and Gravitational Variation of a in Atomic Dysprosium. Arman Cingöz JILA/NIST Boulder, CO. University of California at Berkeley. Variation of Constants & Violation of Symmetries, 24 July 2010. Partial support by:. Coworkers. Dmitry Budker , Nathan Leefer

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A Search for Temporal and Gravitational Variation of a in Atomic Dysprosium

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  1. A Search for Temporal and Gravitational Variation of a in Atomic Dysprosium ArmanCingöz JILA/NIST Boulder, CO University of California at Berkeley Variation of Constants & Violation of Symmetries, 24 July 2010 Partial support by:

  2. Coworkers Dmitry Budker, Nathan Leefer Physics Department, University of California, Berkeley Collaborators Steve Lamoreaux Yale University Alain Lapierre TRIUMF, Canada A.-T. Nguyen University of Pittsburgh Justin Torgerson Los Alamos National Laboratory ValeriyYashchuk and Sarah Ferrell Lawrence Berkeley National Laboratory

  3. Outline • Overview & motivation • Nearly degenerate levels in dysprosium • Experimental technique • Variation Results/ Status Update • Laser Cooling of Dy

  4. Overview • Variation of a would signify physics beyond the Standard Model and General Relativity. • Violates Local Position Invariance (a component of Equivalence Principle), which states that results of non-gravitational experiments are independent of where and when they are performed • WHEN: Temporal variation of fundamental constants: •  • V. Dzuba et. al., Phys. Rev A 68, 022506 (2003) • V. Dzuba and V. V. Flambaum, Phys. Rev A 77, 012515 (2008) • WHERE: Null gravitational redshift experiment: compare two different clocks side by side at the same location • Recast species dependent shift in terms of gravitational variation of a • V. V. Flambaum, Int. J. Mod. Phys. A22, 4937 (2007) 

  5. D3 MHz – 1 GHz B A (t) transitions in 5 isotopes Ÿ dD/dt ~2.0 x 1015 Hz |a/a| V. Dzuba et al, Phys. Rev A 77, 012515 (2008) Ÿ • For |a/a| ~ 10-15 /yr  dD/dt ~ 2 Hz/yr Search in Atomic Dy • Atomic dysprosium (Dy, Z=66) has two nearly degenerate levels that are highly sensitive to a.

  6. Self-heterodyning Optical Comparison • Opposite parity levels  can induce direct electric dipole transitions between levels • DE ~ 3-1000 MHz can induce transitions with an rf electric field • Direct frequency counting  relaxed requirements on reference clock[DE=1 GHz requiresDn/n~10-12 for a mHz measurement (|a/a| ~ 10-18 /yr )] • Essentially independent of other fundamental constants Ÿ A n1 - n2 B n1 n2 G

  7. Statistical Sensitivity • Transition linewidth, g, is determined by the lifetime of • state A (t=7.9 ms)g~20 kHz • Counting rate ~ 109 s-1 • Statistical sensitivity: • dn ~ g/N1/2~ 0.6 Hz s1/2 • T1/2 • After 1 hour of integration time, dn~10 mHz which corresponds • to a sensitivity of: • |a/a| ~ 5 x 10-18 yr-1 Ÿ

  8. Additional Correlations B w1 A A w2 B w1 + w2Þ insensitive to a variation w1 - w2Þ avariation is twice as large Currently we monitor: 3.1-MHz transition in 163Dy 235-MHz transition in 162Dy

  9. Parity Nonconservation in Dy • Degeneracy between levels A and B useful for enhancing mixing due to the weak interactions • Detect quantum interference beat between Stark and PNC mixing • |Hw|=|2.3 ± 2.9 (stat) ± 0.7 (sys)| Hz • A. T. Nguyen et al., PRA 56, 3453 (1997) • Theoretical calculations are difficult since dominant configurations do not mix; effect due to configuration mixing and core polarization • Hw=70 (40) Hz • V. A. Dzuba et al., PRA 50, 3812 (1994) • Recently, improved calculations suggest Hw ~ 2-6 Hz • V. A. Dzuba and V. V. Flambaum, PRA 81, 052515 (2010) • Stay tuned for CW PNC experiment with improved statistical sensitivity

  10. 1397 nm 669 nm 833 nm Population 3 step population scheme: Step 1 and 2:cw laser excitation Step 3: spontaneous decay with b.r. ~30%

  11. Detection • FM modulated rf field transfers population to state A • State A decays to the ground state in two steps • 564-nm light is detected RF 4829 nm 564 nm

  12. First Generation Apparatus Results . a/a = (-2.4 ± 2.3) x 10-15 yr-1A.Cingöz et al., PRL 98, 040801 (2007) ka=(-8.7 ± 6.6) x 10-6S. Ferrell et al., PRA 76, 062104 (2007)

  13. E G 2nd Generation Apparatus 3 F 2 1 D A C B A. Dy effusive oven B. Collimator C. Laser access port D. Two-layer magnetic shield E. 4p Optical collection system F. PMT viewport G. Rf electrodes • Differentially pumped chambers • Oven chamber • Gate valve • Interaction chamber

  14. Current Status • Operational for the past two years • Collisional shifts reduced to ~ 10 mHz • Shifts due to rfinhomogeneities consistent with 0 at the 10 mHz level • However there were unexpected problems: • DC Stark shifts due to stray charge accumulation: problem mostly for 3.1 MHz transition • Zeeman shifts: Dn/B=DgABmomFmax~2 kHz/1mG • Zeeman shifts under control at the ~0.1 Hz level • Stray electric fields mostly stabilized but need further investigation . a/a = (-0.8 ± 2.1) x 10-15 yr-1

  15. Future: Residual Amplitude Modulation • RAM on top of FM creates asymmetric sideband amplitudes which leads to apparent shift of zero crossing for 1st harmonic • Due to the large linewidth, RAM is a serious problem •  ~450 Hz/% RAM • Measured value in our system • ~1 x 10-4  4 Hz shifts • Various ways to control: • Choose proper phase angle • Active stabilization

  16. Laser Cooling of Dy • Increase beam brightness • A better control of beam density • Study self collisions • Reduce systematics due to • spatial inhomogeneities • A strong cycling transition exists • 421 nm (t = 4.6 ns) • However, many decay channels • Calculations suggested B.R. of <10-4 • V. A. Dzuba and V. V. Flambaum, PRA 81, 052515 (2010)

  17. Laser Cooling of Dy • 421 nm source: 1cm PPKTP in a bow tie cavity • 90 mW out with 335 mW IR, 27% c.e. • Transverse cooling experiment: • 3 cm interaction region: ~5000 cycles • Probe velocity distribution w/ 658 nm transition 421 nm Rec. vel. 0.6 cm/s Doppler limit 20 cm/s Doppler temp. 0.8 mK 658 nm • Fit to Voigt Profile: • Gaussian width of 0.8(5) MHz • Lorentzian width of 4.2 (7) MHz • Limit on branching ratio: < 5 x 10-4 • More stringent limit from MOT experiment in Urbana-Champaign: 7 x 10-6 • M. Lu et al., PRL 104, 063001 (2010) N. Leefer et al., PRA 81, 043427 (2010)

  18. Conclusion • The nearly degenerate levels in dysprosium are highly sensitive to a variation. Direct frequency counting techniques allow for measurements without state-of-the-art atomic clocks. • First generation apparatus sensitivity is ~10-15 yr-1 • Second generation apparatus sensitivity is expected to be ~10 -17 yr-1. Actual data taking will commence soon. • Transverse cooling of Dy to the Doppler limit has been demonstrated for all isotopes with large abundance. • XUV Frequency Combs: Monday Poster Session (Mo 89)

  19. Systematic Effects A.- T. Nguyen et al. PRA Phys. Rev. A 69, 022105 (2004) • However, it is not the size but the stability of these effects that is important preliminary analysis showed that systematic effects may be controlled to a level corresponding to |a/a| ~ 5 x 10-18 /yr .

  20. Search in Atomic Dy

  21. Lock-in Detection Technique • rf field is frequency modulated at 10 kHz with a modulation index of 1 • Reduces asymmetries in the line shape caused by drifts (laser and atomic beam fluctuations) • Currently use the ratio of these two harmonics First Harmonic Second Harmonic

  22. Laser Cooling of Dy

  23. Stray B-fields • If unresolved Zeeman sublevels are: • sym. populated leads to broadening , but no shifts • asym. populated leads to broadening and shifts • Dn/B=DgABmomFmax~2 kHz/1mG • Nominal config.: linearly polarized pop. beams aligned state; no shifts • Systematic due to: spatially varying stress-induced birefringence on optics. • run-to-run variations due to laser pointing variations.

  24. RF Interaction Region • Standing Wave • Small radiative losses (closed wave guide) • Impedance matched • Transparent to light • Transparent to the atomic beam • Homogeneous electric field (no phase shifts) • Broadband: 3 MHz to 1 GHz

  25. RF Interaction Region

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