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

2

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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Argonne National LaboratoryRadium EDM Experiment

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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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14

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.

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“Desperate Trappers”

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http://wwwhttp://www--mep.phy.anl.govmep.phy.anl.gov

Argonne

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The End