status of the search for an edm of 225 - g-2 at boston...
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Status of the Search for an EDM of 225Ra
Roy HoltLepton Moments 2006
Cape Cod
I. Ahmad, K. Bailey, J. Guest, R. J. Holt, Z.-T. Lu, T. O’Connor, D. H. Potterveld, N. D. Scielzo
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Outline
Why is an EDM interesting?
Why use radium?
How to detect an EDM
Our plan: Source, MOT, FORT, EDM
Status and Schedule
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EDM Violates Both P and T
+-
+-
-+
T P
EDM Spin EDM Spin EDM Spin
A permanent EDM violates both time-reversal symmetry and parity
Neutron, Deuteron
Diamagnetic Atoms (199Hg, 225Ra, 223Rn)
Paramagnetic Atoms (Tl)Molecules (PbO)
Quark EDM
Quark Chromo-EDM
Electron EDM
Physics beyond the Standard Model:
SUSY
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Standard Model EDM’s are due to CP violation in CKM matrix (K0-system) but…– e- and quark EDM’s are zero at Tree Level.– Need at least third order to get EDM’s.
• Thus EDM’s are VERY small in the Standard Model.
Origin of EDM’s
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The LHC is on the way.
• The LHC doesn’t see evidence for new physics.
Window of opportunity for low energy tests to makediscovery before ILC.
• The LHC observes new physics, say, SUSY.
SM has many new parameters.Low energy experiments willbe necessary to pin downnew parameters.
Two Possibilities:
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Current Experiments in Nuclei
Isotope Current Limit (e cm)
Institution Nuclear Spin Factor of Improvement
T-oddSensitivity
Technique
199Hg -(1.1 ± 0.6)E-28Washington
(0.7 ± 3.3)E-27Michigan
N/A
223Rn N/A Michigan&TRIUMF
7/2 ~ Hg 2000 Cell
D N/A BNL, IUCF, KVI
1 ~Hg 10-103
Washington 1/2
Storage ring
5.6 4 cells
129Xe Princeton 1/2
2-4
102 – 105 0.47 Liquid cell
225Ra ArgonneKVI
1/2 2100 Trap~ Hg
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Schiff moment of 199Hg, de Jesus & Engel, PRC72 (2005)Schiff moment of 225Ra, Dobaczewski & Engel, PRL94 (2005)
Ψ− = (|+⟩ − |−⟩)/√2
Ψ+ = (|+⟩ + |−⟩)/√255 keV
|+⟩ |-⟩
Skyrme Model Isoscalar Isovector Isotensor
SkM* 1500 900 1500
SkO’ 450 240 600
Enhancement Factor: EDM (225Ra) / EDM (199Hg)
EDM of 225Ra enhanced:• Large intrinsic Schiff moment due to octupole deformation;• Closely spaced parity doublet;• Relativistic atomic structure.
Haxton & Henley (1983)Auerbach, Flambaum & Spevak (1996)
Engel, Friar & Hayes (2000)
EDM of 225Ra enhanced
NB: Must include quadrupole term in Schiff operator: See C.-P. Liu et al, nucl-th/0601025
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EDM MeasurementEDM Measurement
B
μ, s
E
d, s
Bs
E Bs
E2 2hf B dEμ+ = + 2 2hf B dEμ− = −
Parameters
--------------------
B = 10 mGauss
f = 11 Hz
E = 100 kV/cm
f+ - f- = 10 nHz
d = 1 x 10-28 e cm
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Expected Statistical Accuracy
No. of Ra atoms:10 mCi source = 3.6 x 108 Ra/s
N = 1 x 107 atomsTrap storage time = 300 s
E = 100 kV/cmT = 100 daysDetection efficiency = 0.05
Enhancement factor: Ra/Hg = 375
Best experimental limit:
M. C. Romalis et al, PRL 86 (2001) 2505
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Search for EDM of Search for EDM of 225225RaRaAdvantages of an EDM measurement on 225Ra atoms in a trap:• Trap allows a long coherence time (~ 300 s).• Cold atoms result in a negligible “v x E” systematic effect.• Trap allows the efficient use of the rare and radioactive 225Ra atoms.• Small sample in an XHV allows a high electric field (> 100 kV/cm).
225RaNuclear Spin = ½Electronic Spin = 0t1/2 = 15 days
Proposed setup
Atomic Beam
Magneto-OpticalTrap
TransverseCooling
Oven
10 mCi225Ra sample
Fiber-Laser Optical Dipole Trap
EDM-probing region
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Radium Atom Energy Level DiagramRadium Atom Energy Level DiagramDzuba et al., PRA 61, 062509 (2000)
Laser-cooling on 1S0-3P1:~2x104 cycling transitions
422 ns lifetime*Accel ~ 3000 m/s2
1 G/cm MOT gradientkBT = h/(2τ) ~ 10 μK
7 ms cooling w/o repump
7s2 1S0
7p 3P0°
7p 3P1°
7p 3P2°
6d 3D2
6d 3D3
6d 3D1
6d 1D2
7p 1P1°
422 ns*
38 ms
5.5 ns
600 μs?
Lase
r-coo
ling:
714
nm
1
100
9e-2
2e-5
5e-7
1e-1
5e-2
4e-3
1e-9
Repump: 1428 nm
6e-5
9e-4
1e-1
2e-2
*N. D. Scielzo et al., PRA 73, 010501 (2006)
Repump on 3D1-1P1:8 s cooling w/ repumpTransition frequency?
Isotope shift?Hyperfine splitting?
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225225Ra SourceRa Source
229Th7300 yr
225Ra15 days
225Ac10 days
209Bistable
Fr, At, Rn…~ 4 hours
α αβ α,β
• 10 mCi 229Th source produces 4 x 108 s-1 225Ra
Test source: 0.5 mCi 229Th
• Chemical extraction of Ra from Th
• Reduction of Ra(NO3)2 with Ba, Al, Ti…
Exotic Beam Facility ~ 1 Exotic Beam Facility ~ 1 CiCi 229229ThThExpected yield for 225Ra: 3 x 1010 s-1
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225Ra
225Ac
40 keV γ-ray
t1/2=14.9 d
30%
70%
10
2
46
100
2
46
10002
Cou
nts
700600500400300200Energy (keV)
221Fr 213Bi
137Cs
β−
221Fr
α
217At
218 keV γ-ray
α
12%
213Bi
α
213Po
α
26%441 keV γ-ray
γ
γ
γ
2
3
4567
1000
2
3
Cou
nts
50403020Energy (keV)
225Ra
137Cs
Window Facing Oven Aperture Unused Window
α
13 October 03 experiment
225Ra from the Oven
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Spectroscopy and lifetime measurementSpectroscopy and lifetime measurement
Ba and Ra atomic beam
Notch filter
PMT
Oven @ 700 C
Transverselaser beam
6s2 1S0
6p 3P1
5d 3D1
~1200+-100 ns *
1 1
Barium
5d 3D2
0.3791.1 nm
7s2 1S0
7p 3P1
~250-500 ns
1
Radium
714.3 nm
250 μCi ~ 5 nano-g 225Ra+ 100 mg Ba
6d 3D1
6e-5
*H. Bucka et al., Ann. Physik 8, 329 (1961)
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Fluo
resc
ence
225225Ra SpectroscopyRa Spectroscopy
1S0 |F=1/2> -> 3P1 |F=3/2>13999.267(1) cm-1
Laser locking transition
13999.23 13999.25 13999.27
Iodi
ne s
igna
l
Wavenumber (cm -1)
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Ra 7s7p Ra 7s7p 33PP1 1 lifetime measurementlifetime measurement
0 500 1000 1500 2000
Fluo
resc
ence
Time (ns)
τ = 422 ns +- 20 ns
0
N. D. Scielzo et al., PRA (2006)
Lifetimemeasurement cycle:
FluorescenceExcitation laser
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0
500
1000
1500
2000
2500
6999.83 6999.84 6999.85
1 P1-1 S
0 pho
ton
coun
ts
Wavenumber (cm-1)
Repump transition in 226Ra beam
3D1 -> 1P1
6999.83(1) cm-1
(1428.606 nm)3D1
1S0
1P1
3P1
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Radium slower and trapRadium slower and trap
Transverse cooling
MOT
Slower
Slower, Trans cooling, MOT
phase~400 ms
~50 msProbe phase
1 μs
Repump
Zeeman slower
750 nCi 226Ra (600 nano-g)1 mCi 225Ra (20 nano-g)
PMT
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Laser-Trapping of Radium Atoms
• World’s first laser trap of radium atoms: both 225Ra and 226Ra atoms are cooled and trapped!
• Key 225Ra frequencies, lifetimes measured.
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Laser-Trapping of Radium Atoms
• World’s first laser trap of radium atoms: both 225Ra and 226Ra atoms are cooled and trapped!
• Key 225Ra frequencies, lifetimes measured.
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Overall Trap EfficiencyOverall Trap Efficiency
Atomic Beam
Magneto-OpticalTrap
TransverseCooling
Oven
225Ra sample
• Monte Carlo estimate: 3 x 10-6
• Observation: 7 x 10-7
• Original proposal: 1 x 10-4
Future Improvements:• Improved transverse cooling: x 2-10• Longer slower: x 2• Re-pump along slower: x 3
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Optical Dipole TrapOptical Dipole Trap
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H dE Eα= − = −%
( )2Excitation rate ~laser atom
Intensityf f− ( )
Trap potential ~laser atom
Intensityf f−
• Erbium Fiber laser: λ = 1.5 μm, Power = 5 Watts
• Focused to 50 μm diameter trap depth 100 μK
• Excitation rate ~ 10-5 s-1
• Spin relaxation rate ~ 10-20 s-1 negligible
M. V. Romalis and E. N. Fortson, PRA 59 (1999) 4547
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EDM MeasurementEDM Measurement
7s2 1S0F = 1/2
7p 3P1F = 1/2
mF = -1/2
mF = +1/2
mF = +1/2
mF = -1/2
σ+ Excitation
σ-
Fluorescence
Dipole trap beam
Polarizing and probinglaser beam
EB
E field plates
Pol.
1. Polarize2. π / 2 pulse3. Free precess4. π / 2 pulse5. Measure population
P PP P
+ −
+ −
−+
fdrive - fatom
E up
E down
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2003 – Establish Ra lab, prepare Ra oven and beam
2004 – Stabilize laser and perform laser spectroscopy of 225Ra, improve oven
2005 – Establish MOT of Ra atoms
• 2006 – Establish optical dipole trap
• 2007 – Begin EDM experiment
• 2008 - Improve statistics and systematics
• 2009 - …
Milestones
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Summary
• New initiative at Argonne to search for the EDM of 225Ra
• Combined advantages of optical trapping and the use of an octupole deformed nucleus
• Ultimate goal of at least x 100 improvement in sensitivity over previous experiments
• Radium-225 atoms have been optically trapped.