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Search for the Electron Electric Dipole Moment. Experiment: D.DeMille, D. Kawall, R.Paolino, V. Prasad F. Bay, S. Bickman, P.Hamilton, Y. Jiang, Y.Gurevich Yale University L.R.Hunter (Amherst) Theory: M. Kozlov ( PNPI, St. Petersburg) , D. DeMille. Val Prasad Yale University. D. S. - PowerPoint PPT Presentation
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Search for the Electron Electric Dipole Moment
Val Prasad
Yale UniversityExperiment:
D.DeMille, D. Kawall, R.Paolino, V. Prasad
F. Bay, S. Bickman, P.Hamilton,
Y. Jiang, Y.Gurevich
Yale University
L.R.Hunter (Amherst)
Theory:
M. Kozlov (PNPI, St. Petersburg),
D. DeMille
An EDM Violates Parity and Time Reversal Symmetries and may provide evidence of
new physics
T-violation: a window to new physics
P T
D S
look different after P reversal
look different after T reversal
CPT theorem T-violation = CP-violation
Feynman Diagram
ee
2
5 Fde
d L
not renormalizable loop diagrams
Std Model: Standard ModelLR-S: Left-Right SymmetricL-FC: Lepton flavor-changingM-H: Multi-HiggsTC: TechnicolorAC: Accidental Cancellations
HsF: Heavy sFermionsA-CP: Approx. CPA-Un: Approx UniversalityAlign: AlignmentE-Un: Exact Universality
M-H
NAIVE SUSY
AC A-CP
A-Un
Align
HsF
SO(10) GUT
LR-S
L-FC
TC
10-26 10-28 10-30
de (e·cm)
Berkeley Yale I (projected)
10-32
E-Un
10-40
Std Model
Experimental limit: |de| < 1.610-27 ecm (Berkeley)
Yale II (projected)
Theoretical Predictions for de
General Method to Detect an EDM
dEB 0
dEB 0
dEB 0
spin
E
B dEB 0
Energy ShiftResolution
~ ____(de.Eeff)_______ (Tcoh .√(dN/dt Tmeas))-1
Schiff’s theorem
magneticelectric
magneticelectrictotal
FF
FFF 0
crBmagvE
BF ~
Near nucleus, v, E, large + substantial amplitude for valence e-:r ~ a0/Z; v ~ Zc; E ~ Ze/r2; B ~ea0; (0) ~Z1/2
|<Eeff>| Z32 (e/a02) P
Cannot apply an electric field to a free electron for long times
Use a neutral object (atoms, molecules)
Molecules enhance electric fields
Atoms• Large laboratory fields ~50
kV/cm• Leakage currents=BAD!!!• Smaller enhancement
factors
Pb
OE
Eext~10 V/cm
Eint~1010 V/cmMolecules
• Unpaired electron=free radical
• Boltzmann distribution over many rovibrational states
M. G. Kozlov and D. DeMillePhys. Rev. Lett. 89, 133001 (2002)
An aside: what’s an -doublet?
-90 0 90 180 270angle to molecular axis
En
erg
y
Symmetric-antisymmmetric states split by tunneling
=0
=-1=+1
=1 states coupled in 2nd order viamolecular rotation (Coriolis)E ~ (Erot)2/Est ~ 10-3Erot
LSJe
...
En
,
Non-rotating moleculehas internal
tensor Stark shift
22 eSt JnE
Thallium vs PbO*Atom/Molecule Thallium PbO*
Group Berkeley Yale/Amherst
Applied field (V/cm) 105 >15
Effective field (V/cm) 6107 3-61010!!
Coherence time T (ms) 3 0.1
Count rate (1/s) 2109 1011
Figure of merit 1 240
Projected sensitivity (ecm) 210-28 10-29/10-31
Present limit (ecm) <1.610-27 ???
PbO*: ΔEedm = 2.5 x 1025 Hz x de (e-cm)
Excitation scheme
0+
1-
2+
X(0)[1Σ+]
1-
1+
2+
2-
a(1) [3 Σ+]
~10 GHz
~12 MHz
Laser pulseλ~571 nmt~10 nsBandwidth~1GHz~ΔνDoppler
R0 208PbJ’’=0→J’=1
Molecular Spectra
R0(J”=0J’=1-)208Pb
X(v’’ = 1) a(v’ = 5) excitation ( = 571 nm)a(v’ = 5) X(v’’ = 0) detection ( = 548 nm)
Integrated over ~200 s after each pulse
Tune laser here
Inte
gra
ted
in
ten
sit
y
Omega Doublet
e|
f|
2
|| fe
m=-1 m=0 m=1
B =0 E =0
νZeeman~300 kHz
2
|| fe
ν~11.2 MHz
MHzStark 6020~
Excitation Scheme
B E
RF pulse
-2 -1 1 2
0.2
0.4
0.6
0.8
1
dEB 0
Excitation Scheme
B E
RF pulse
-2 -1 1 2
0.2
0.4
0.6
0.8
1
dEB 0
Excitation Scheme
B E
RF pulse
-2 -1 1 2
0.2
0.4
0.6
0.8
1
dEB 0
Quantum Beats• Coherent superposition of two states decaying to
the same state• Precession frequency proportional to energy
difference between states• Allows for Doppler free, very precise
spectroscopy (<1mHz)
x
y
Present Experimental Setup
Photomultiplier tube
Si gnal
Frequency
Solid quartz light pipes
DataProcessing
integral
Vacuum chamber
Fourier Transform
PbO vapor Cell
B
•A specialized oven to heat a novel vapor cell to temperatures of 700°C•The cell contains about 80cm3 of PbO vapor of natural isotopic abundance •Vacuum chamber surrounded by 3 orthogonal Helmholtz coils•Use Nd:YAG pumped dye laser at 570nm, 5-40 mJ /pulse, 1 GHz linewidth•Excite X(0)a(1) transition and detect quantum beat fluorescence signal•Analyze beat frequency•Perform reversal of E field, B field or RF transition to measure dipole induced frequency shift
PbO Vapor Cell
Main electrode
Guard ring
Sapphire window
•Re-entrant electrodes for homogeneous E field•Flat windows to reduce scattered light and birefringence•Larger volume to reduce wall quenching
Quartz Oven•Can withstand repeated thermal cycling to 800°C•~1300 W of power used•Excellent Temperature stability •wide optical access•low-inductance heater for fast switching
Magnetic Shield
Winston Cone
Quartz Oven Parts
Peripherals To EDM Experiment
Systematics Considerations
• Motional Magnetic Fields
• Magnetic Noise
• Leakage Currents
• Multi-photon ionization
• E-field gradients
• Inhomogeneities in E-field
• Stray B-fields and E-fields
B EBrf
B EBrf
B EBrfB EBrf
Ћ rf ΔEstark
Ћ rf ΔEstark
+ ΔE -doublet
E reversal
Frequency for de=0
Frequency for de≠0
Dashed-line energy levels show Zeeman shifts. Dotted-line levels show the additional linear Stark shift which would arise from a non-zero EDM.
-doublet levels = comagnetometer: Most systematics cancel in comparison
rf tuning adds NEWreversal to the EDM measurement
EDM Measurement in PbO*New mechanisms for suppressing systematics!
g-factor measurement
Results help constrain calculation of enhancement-factor
008.0857.1 : and 0.0081.860 :
gJgJ
ideal) 0g
g ( 0.002
g
g
g
g
g -doublet useful as Co-Magnetometer
To what extent is the - doublet a perfect mirror image?
SBgH B
Typical Data
Averaged over 0.5 s, Bz~60 mG
Rabi Flopping56 RF cycles
-4.E-04
-2.E-04
0.E+00
2.E-04
4.E-04
6.E-04
8.E-04
1.E-03
1.1E+07 1.1E+07 1.1E+07 1.1E+07 1.1E+07 1.2E+07 1.2E+07
RF frequency (Hz)
beat
freq
uen
cy c
han
ge (
MH
z)
Stark Shift = Zeeman Shift
Omega Doublet
e|
f|
2
|| fe
m=-1 m=0 m=1
B =0 E =0
νZeeman~300 kHz
2
|| fe
ν~11.2 MHz
MHzStark 6020~
Current sensitivity to quantum beat frequency
1X10-27e.cm corresponds to beat frequency shift 10-25mHz
Straightforward modification to improve sensitivity to
Two photodiodes with high quantum efficiency instead of single PMTExcite from X(0)(v”=0) instead of X(0)(v”=1)Use broader band interference filtersUse isotopic enriched 208PbO…
Expect to increase the count rate by more than three orders of magnitude, and the contrast by more than a factor of two
Current Sensitivity
The necessary modifications are now underway
1X10-29e·cm corresponds to 100-240μHz T < 106s
Two orders of magnitude improvement on de in ~10days
Average for T=25s
100mHz / Hz
100mHz 120mHz
Hz Tv
Conclusions
• Many preliminary steps have been successfully demonstrated
• Improvements in excitation and detection efficiencies look promising
• Attacking a few remaining experimental issues before we take a first look at the data …………….
Density determined by collisional quenchingAdjust PbO density so excited state decay rate ~collisional quenching rate1/ a(1) ~σnv, where a(1) ~ 80 μsMeasured σ~10-14cm2 n=3x1013cm-3 P=0.3mTorr T=690oC v=3x104cm/s
Minimum cell size determined by wall quenchingv x a(1) < L L~5cm
Density and cell size determine number of molecules in usable rovibrational state
f~B/kBT~0.3cm-1/670cm-1 3x10-4
S/ N estimated from laser power, cross sectionNumber of molecules excited/pulse(100Hz) ~1010
Number of photoelectrons detected /excited molecule ~ fewx10-5
Total fluorescence rate ~ 107/secBackground from blackbody radiation comparable to fluorescence
Current Operating Condition
contrast fluorescence~ ~ 200 /
background
Ss
N