Atomic parity violation in ytterbium

Atomic parity violation in ytterbium

Dmitry BudkerUniversity of California, Berkeley

Nuclear Science Division, LBNL

http://socrates.berkeley.edu/~budker/http://socrates.berkeley.edu/~budker/

PREX Workshop

JLAB, August 16-18, 2008

2

Outline

MotivationThe Yb systemMeasurement principleApparatusPreliminary parity-violation resultsExperimental issuesOutlook (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)

• But enhanced sensitivity to the neutron distribution n(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

• 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

Anapole Moments

PNC within nucleus !

probe of weak meson couplings

• 1997 C. E. Wieman and co-workersCs AM detected !

• 1995 E.N.Fortson and co-workersTl AM – small…

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Atomic Yb: energy levels and transitions

PNC amplitude: 10-9e·a0

DeMille (1995)

+5d6p

|M1|10-4 μB

J.E. Stalnaker, et al, PRA 66(3), 31403 (2002)

β2·10-8 ea0/(V/cm)C.J. Bowers et al, PRA 59(5), 3513 (1999); J.E. Stalnaker et al, PRA 73,

043416 (2006)

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Stark-PV-interference

Geometries and invariants:

B E B E B

9

PV effect on line shapes:PV effect on line shapes:even isotopeseven isotopes

0 2 2 2

2 21 2

E (E,0,0)ε (0,sinθ,cosθ)

R E sin θ 2 E sin θcosθ

ER cos θ E sin θcosθ2

PV-Stark PV-Stark interference interference termsterms

168,170,174,176Yb or

θ

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PV effect on line shapes:PV effect on line shapes:odd isotopesodd isotopes

2 22 2FF

FF

2 22FF

FF

E (E,0,0)ε (0,sinθ,cosθ)

β ER (4sin θ cos θ) β E sin θcosθ6

β ER cos θ β E sin θcosθ2

center

side

NSDI J

NSD~10-11 ea0

for odd Yb isotopes

=10-9 ea0

` must be measured with 0.1% accuracy

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Electric and magnetic fields define handednessThe Yb PNC Experiment

Rotational Invariant: B E B

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Optical system and control electronics

Light powers:Ar+: 15WTi:Sapp (816 nm): 1 WDoubler (408 nm): 50 mWPBC:Confocal design, 25 cm;Finesse ~10,000 (upgrading to 40000 ??)

Locking:Pound-Drever-Hall technique

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Typical signal

• 174Yb resonance split by B70 G; E=3 kV/cm

• Expected PV asymmetry: ~ 2·10-4/ E/(kV/cm)

• Asymmetric lineshape ← AC Stark effect

1414

Atoms in electric fieldAtoms in electric field: : the the StarkStark effecteffect

oror LoSurdo LoSurdo phenomenonphenomenon

Johannes Stark (1874-1957)

Nazi Fascist

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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→

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Reversals and pseudo-reversals

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Statistical Sensitivity

• With parameters presently achieved, the shot noise limit is:

• 10 hrs should correspond to a 0.5% measurement…

( )PV

S T sN

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)

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2

21

2121

2

2

FTTP

P

LLTTF

in

trans

C. J. Hood, H. J. Kimble, J. Ye. PRA 64, 2001

-10 -5 0 5 100.00

0.05

0.10

0.15

0.20

=1.33 s F=5698

=1.74 s F=7454

PBC

tran

smis

sion

[V]

Time [s]

=2.16 s F=9253

Power-buildup cavity design and characterization

Ringdown spectroscopy

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Power-buildup cavity design and characterization:

mirrors

REO set1=408 nm

REO set2=408 nm

ATF=408 nm

Boulder expt=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

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-60 -40 -20 0 20 40 60

0

20

40

60

80

100

120

-60 -40 -20 0 20 40 60-0.20.00.20.40.60.81.01.21.41.61.8

2d harmonic signal fit

Sign

al A

mpl

itude

[nA

]

1st harmonic signal fit PNC line shape (x10)

f [MHz]

Sign

al A

mpl

itude

[nA

]

The 70-Hz E-modulation schemeto avoid low-frequency noise and drift issues

Due to bias ex 25 V/cm

Different pattern and polarization

dependence for PV

20-s integration

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1 2 3 4 5 6

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

Im(

/) [

V/c

m]

Run number

78(22) mV/cm

Present status: PV results

• About 14 hours of data collection

• Limited by shot noise and stray fields → to be improved

• Systematics checks in progress

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Present status: systematics

1 2 3 4 5 6

-0.020

-0.015

-0.010

-0.005

0.000

0.005

0.010

0.015

0.020

0.025

2(bx e

y)/(B

0 E

dc)

2(bx e

z)/(B

0 E

dc)

BackgroundA

sym

met

ry

Run

Average stray ex-field: 150 mV/cm

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Almost there Verification of PV enhancement

And then… PV in odd isotopes: NSD PV, Anapole Moments PV in a string of isotopes; neutron distributions, …

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

Progress towards measuring PV in Yb

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Yb: the team

K. Tsigutkin A. Family D. Dounas-Frazer post-doc undergrad new grad.student

J. E. Stalnakergrad. student → prof. @ Oberlin

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The parity violation experimentparity violation experiment in Dyevolved into…

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

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18~ 10 / yr

PV with mHz sensitivity

Status: setting up