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Atomic parity violation in ytterbium

Atomic parity violation in ytterbium. Dmitry Budker University of California, Berkeley Nuclear Science Division, LBNL. PREX Workshop JLAB, August 16-18, 2008. http://socrates.berkeley.edu/~budker/. Outline. Motivation The Yb system Measurement principle Apparatus

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Atomic parity violation in ytterbium

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  1. Atomic parity violation in ytterbium Dmitry Budker University of California, Berkeley Nuclear Science Division, LBNL PREX Workshop JLAB, August 16-18, 2008 http://socrates.berkeley.edu/~budker/

  2. Outline • Motivation • The Yb system • Measurement principle • Apparatus • Preliminary parity-violation results • Experimental issues • Outlook (Yb and Dy)

  3. Motivation • Verification of large predicted atomic PV effect (x100 Cs; DeMille, Kozlov et al, Das et al) • Isotopic ratios and neutron distributions (6 stable isotopes; N=8) • Nuclear spin-dependent PV – anapole moments (valence neutrons)

  4. Isotopic ratios and neutron distributions • Atomic PV calculation errors cancel in isotopic ratios Dzuba, Flambaum, and Khriplovich, Z. Phys. D 1, 243 (1986) • Butenhanced sensitivity to the neutron distribution rn(r) Fortson, Pang, Wilets, PRL 65, 2857 (1990) • Atomic PV  Neutron distributions • For 170Yb-176Yb, QW  -100; QW(Standard Model)  6 QW(Neutron Skin)  3

  5. Isotopic ratios and neutron distributions: new development (ArXiv) • Neutron-skin effects in different isotopes are correlated

  6. Anapole Moments Ya . B. Zel’dovich, V. G. Vaks • 1959 AM first introduced V.V. Flambaum, I.B. Khriplovich & • 1980 - 84 O.P. Sushkov Nuclear AM detectable in atoms E.N.Fortson and co-workers • 1995 Tl AM – small… C. E. Wieman and co-workers • 1997 Cs AM detected ! PNC within nucleus! probe of weak meson couplings

  7. Atomic Yb: energy levels and transitions +5d6p PNC amplitude: 10-9e·a0 DeMille (1995) |M1|10-4 μB J.E. Stalnaker, et al, PRA 66(3), 31403 (2002) β2·10-8ea0/(V/cm) C.J. Bowers et al, PRA 59(5), 3513 (1999); J.E. Stalnaker et al, PRA 73, 043416 (2006)

  8. Stark-PV-interference Geometries and invariants:

  9. PV effect on line shapes:even isotopes PV-Stark interference terms 168,170,174,176Yb or θ

  10. PV effect on line shapes:odd isotopes xNSD~10-11 ea0 for odd Yb isotopes x=10-9 ea0 x` must be measured with 0.1% accuracy

  11. The Yb PNC Experiment Electric and magnetic fields define handedness

  12. Optical system and control electronics Light powers: Ar+: 15W Ti:Sapp (816 nm): 1 W Doubler (408 nm): 50 mW PBC: Confocal design, 25 cm; Finesse ~10,000 (upgrading to 40000 ??) Locking: Pound-Drever-Hall technique

  13. Typical signal • 174Yb resonance split by B70 G; E=3 kV/cm • Expected PV asymmetry: ~ 2·10-4/ E/(kV/cm) • Asymmetric lineshape ← AC Stark effect

  14. Atoms in electric field: the Stark effectorLoSurdo phenomenon Johannes Stark (1874-1957) Nazi Fascist

  15. Reversals andpseudo-reversals • E-field reversal (14 ms: 70-Hz modulation) • Lineshape scan (200 ms/point x 100 pts/lineshape = 40 s) • B-field reversal (every few minutes) • Polarization angle (occasionally) • E-field magnitude • B-field magnitude • Angle magnitude For θ=/4→

  16. Reversals andpseudo-reversals

  17. Statistical Sensitivity • With parameters presently achieved, the shot noise limit is: • 10 hrs should correspond to a 0.5% measurement…

  18. But there are some problems: • Photo-induced PBC mirror deterioration in vacuum • Slow drifts • Technical noise (above shot-noise) • Stray electric fields (~ up to a few V/cm)

  19. Power-buildup cavity design and characterization C. J. Hood, H. J. Kimble, J. Ye. PRA 64, 2001 Ringdown spectroscopy

  20. Power-buildup cavity design and characterization: mirrors * Substrates were provided by Rainbow Research Optics, Inc, Denver, CO Finesse of 29000 seen with REO mirrors Photodegradation is still a problem Locking electronics needs work

  21. The 70-Hz E-modulation schemeto avoid low-frequency noise and drift issues 20-s integration Due to bias ex  25 V/cm Different pattern and polarization dependence for PV

  22. Present status: PV results • About 14 hours of data collection • Limited by shot noise and stray fields → to be improved • Systematics checks in progress

  23. Present status: systematics Average stray ex-field: 150 mV/cm

  24. Progress towards measuring PV in Yb Completed Work • Lifetime Measurements • General Spectroscopy (hyperfine shifts, isotope shifts) • dc Stark Shift Measurements • Stark-Induced Amplitude (β): 2 independent measurements • M1 Measurement (Stark-M1 interference) • ac Stark shifts measured Almost there • Verification of PV enhancement And then… • PV in odd isotopes: NSD PV, Anapole Moments • PV in a string of isotopes; neutron distributions, …

  25. Yb: the team K. Tsigutkin A. Family D. Dounas-Frazer post-doc undergrad new grad.student J. E. Stalnaker grad. student → prof. @ Oberlin

  26. The parity violation experiment in Dy evolved into…

  27. a/a = (-2.9 ± 2.6mostly syst) x 10-15 yr-1 Phys. Rev. Lett. 98, 040801 (2007)

  28. PV with mHz sensitivity Status: setting up

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