Atomic parity violation in ytterbium
description
Transcript of 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
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Outline
MotivationThe Yb systemMeasurement principleApparatusPreliminary parity-violation resultsExperimental issuesOutlook (Yb and Dy)
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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)
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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
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Isotopic ratios and neutron distributions: new development (ArXiv)
• Neutron-skin effects in different isotopes are correlated
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• 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
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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
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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
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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