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K. Tsigutkin, J. Stalnaker, V. Yashchuk, D. Budker

Parity nonconservation in the 6s 2 1 S 0 – 6s5d 3 D 1 transition in Atomic Ytterbium: status of the Berkeley experiments. K. Tsigutkin, J. Stalnaker, V. Yashchuk, D. Budker Department of Physics,University of California, Berkeley. Weak interaction in Atoms.

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K. Tsigutkin, J. Stalnaker, V. Yashchuk, D. Budker

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  1. Parity nonconservationin the 6s21S0 – 6s5d 3D1 transitionin Atomic Ytterbium:status of the Berkeley experiments K. Tsigutkin, J. Stalnaker, V. Yashchuk, D. Budker Department of Physics,University of California, Berkeley

  2. Weak interaction in Atoms Nuclear spin independent contribution Nuclear spin dependent term kA-Anapole moment kA-Neutral currents kQW-Radiative corrections Khriplovich & Flambaum ma-Magnetic moment in terms of nuclear magneton ga-Weak coupling constant of the unpaired nucleon C2a- Coupling constants for the valence nucleon Unpaired neutron: mn=-1.2; gn=-1 Unpaired proton: mp=3.8; gp=5 Anapole moment is much bigger for nuclei with unpaired proton *C.Wood et al, Science 1997. (Univ. of Colorado, Boulder) ** J. Guéna, M. Lintz, and M. A. Bouchiat PRA 2005 *** P. Vetter et al, PRL 1995. (Univ. of Washington, Seattle)

  3. Signature of the weak interaction in atoms HPNC mixes |ns1/2> and |n`p1/2> states of valence electron  APNC of dipole-forbidden transition. If APC is also induced, the amplitudes interfere. APCA’PCinterference Interference E1-PNC interference term is odd in E E-field Stark-effect E1 PC-amplitude  E MUST: Determine APC with high precision Limit A’PC Reversing E-field change the transition rate. Transition rate  APNCAStark

  4. Atomic structure of Yb By observing the 6s21S0 – 6s6p 3P1 556 nm decay the pumping rate of the 6s21S0 – 6s5d3D1 408 nm transition is determined. In addition, the population of 6s6p 3P0 metastable level is probed by pumping the 6s6p 3P0 - 6s7s 3S1 649 nm transition.

  5. Yb isotopes and abundances C.J. Bowers et al, PRA 1999

  6. Rotational invariant and geometry of the Yb experiment Rotational invariant to which the PNC-Stark interference term is proportional is chosen so that E is along the excitation light axis. This suppresses the interference between M1 and Stark amplitudes emphasizing the PNC-Stark contribution. Reversals: B – even E – odd q qp/2 – odd q q+p – even |b| = 2.24(25)10-8 e a0/(V/cm) – Stark transition polarizability (Measured by J.Stalnaker at al, PRA 2006) |d| = 1.08(24)10-9 (QW/104) e a0/(V/cm) – Nuclear spin-independent PNC amplitude (Calculations by Porsev et al, JETP Lett 1995; B. Das, PRA 1997 )

  7. PNC effect on line shapes:even isotopes PNC-Stark interference terms 176Yb Rate modulation under the E-field reversal yields:

  8. PNC effect on line shapes:odd isotopes PNC-Stark interference terms 171Yb dNSD10-12 ea0 for odd Yb isotopes d=10-9 ea0 d` must be measured with 0.1% accuracy

  9. Experimental setup Light collection efficiency: Interaction region: ~2% (556 nm) Detection region: ~25% Yb density in the beam ~1010 cm-3 Reversible E-field up to 15 kV/cm, spatial homogeneity 99% Reversible B-field up to 100 G, homogeneity 99%

  10. Optical system and control electronics Light powers: Ar+: 15W Ti:Sapp (816 nm): 1W Doubler (408 nm): 50 mW PBC: Confocal design, 25 cm; Finesse ~4000 Locking: Pound-Drever-Hall technique

  11. Doppler width and spectral resolution Application of the atomic beam collimator allows to reduce the Doppler broadening by a factor of 10 . Spectral lines of closely neighboring isotopes can be clearly resolved. Scanning over 408 nm line, observing 556 nm fluorescence at the interaction region. Observations of the 649 nm line will contribute to a factor of 10 increase in the sensitivity.

  12. Line shapes under the B-field Under application of B-field line profiles demonstrate predicted shapes Signal averaged over 100 scans Scan rate = 1 Hz Ready to collect data with E-field modulation

  13. Systematic effects E-field inhomogeneity B-field inhomogeneity Distortion of linear polarization of the light Residual light propagation in the PBC M1~300d Terms having same dependence on the leading E-field reversal and same polarization angle dependence as the Stark-PNC interference term must be limited Required: Non-reversing dBx, dEz << 1%

  14. Summary • The program of measurements needed to understand the system is complete. • It is now possible to proceed with confidence towards a first measurement of PNC in Yb • The challenge will then be to refine the system to achieve the fractional precision needed to observe NSD effects.

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