Atomic parity violation in ytterbium Dmitry Budker University

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 Preliminary parity-violation results Experimental issues Outlook (Yb and Dy) 2

Motivation § Verification of large predicted atomic PV effect (x 100 Cs; De. Mille, Kozlov et al, Das et al) § Isotopic ratios and neutron distributions (6 stable isotopes; N=8) § Nuclear spin-dependent PV – anapole moments (valence neutrons) 3

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

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

Anapole Moments • 1959 Ya. B. Zel’dovich, V. G. Vaks AM first introduced • 1980 -84 V. V. Flambaum, I. B. Khriplovich & 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 6

Atomic Yb: energy levels and transitions +5 d 6 p PNC amplitude: 10 -9 e·a 0 De. Mille (1995) |M 1| 10 -4 μB J. E. Stalnaker, et al, PRA 66(3), 31403 (2002) β 2· 10 -8 ea 0/(V/cm) C. J. Bowers et al, PRA 59(5), 3513 (1999); J. E. Stalnaker et al, PRA 73, 043416 (2006) 7

Stark-PV-interference Geometries and invariants: 8

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

PV effect on line shapes: odd isotopes x. NSD~10 -11 ea 0 for odd Yb isotopes x=10 -9 ea 0 x` must be measured with 0. 1% accuracy 10

The Yb PNC Experiment Electric and magnetic fields define handedness 11

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

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

Atoms in electric field: the Stark effect or Lo. Surdo phenomenon Johannes Stark (1874 -1957) Nazi Fascist 14

Reversals and pseudo-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→ 15

Reversals and pseudo-reversals 16

Statistical Sensitivity • With parameters presently achieved, the shot noise limit is: • 10 hrs should correspond to a 0. 5% measurement… 17

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) 18

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

Power-buildup cavity design and characterization: mirrors REO set 1 l=408 nm REO set 2 l=408 nm ATF l=408 nm Boulder expt l=540 nm Transmission 320 ppm 45; 23 ppm 130 ppm 40; 13 S+A losses 120 ppm 213; 83 ppm 800 ppm* <1 ppm * 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 20

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

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

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

Progress towards measuring PV in Yb Completed Work ü ü ü Lifetime Measurements General Spectroscopy (hyperfine shifts, isotope shifts) dc Stark Shift Measurements Stark-Induced Amplitude (β): 2 independent measurements M 1 Measurement (Stark-M 1 interference) ac Stark shifts measured Almost there Ø Verification of PV enhancement And then… Ø PV in odd isotopes: NSD PV, Anapole Moments Ø PV in a string of isotopes; neutron distributions, … 24