Status of the Search for an EDM of 225 Ra I. Ahmad, K. Bailey, J. Guest, R. J. Holt, Z.-T. Lu, T. O Connor, D. H. Potterveld, N. D. Scielzo Roy Holt Lepton Moments 2006 Cape Cod
Outline Why is an EDM interesting? Why use radium? How to detect an EDM Our plan: Source, MOT, FORT, EDM Status and Schedule 2
EDM Violates Both P and T A permanent EDM violates both time-reversal symmetry and parity + T + P - - - + EDM Spin EDM Spin EDM Spin Neutron, Deuteron Diamagnetic Atoms ( 199 Hg, 225 Ra, 223 Rn) Paramagnetic Atoms (Tl) Molecules (PbO) Quark EDM Quark Chromo-EDM Electron EDM Physics beyond the Standard Model: SUSY 3
Origin of EDM s Standard Model EDM s are due to CP violation in CKM matrix (K 0 -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. 4
The LHC is on the way. Two Possibilities: The LHC doesn t see evidence for new physics. Window of opportunity for low energy tests to make discovery before ILC. The LHC observes new physics, say, SUSY. SM has many new parameters. Low energy experiments will be necessary to pin down new parameters. 5
Current Experiments in Nuclei Isotope Current Limit (e cm) Institution Nuclear Spin Factor of Improvement T-odd Sensitivity Technique 199Hg -(1.1 ± 0.6)E-28 Washington Washington 1/2 2-4 5.6 4 cells 129Xe (0.7 ± 3.3)E-27 Princeton 1/2 Michigan 10 2 10 5 0.47 Liquid cell 225Ra N/A Argonne KVI 1/2 ~ Hg 2100 Trap 223Rn N/A Michigan& TRIUMF 7/2 ~ Hg 2000 Cell D N/A BNL, IUCF, KVI 1 ~Hg 10-10 3 Storage ring 6
EDM of 225 Ra enhanced EDM of 225 Ra 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) Enhancement Factor: EDM ( 225 Ra) / EDM ( 199 Hg) 55 kev Ψ = ( + )/ 2 Ψ + = ( + + )/ 2 Skyrme Model Isoscalar Isovector Isotensor SkM* 1500 900 1500 SkO 450 240 600 Schiff moment of 199 Hg, de Jesus & Engel, PRC72 (2005) Schiff moment of 225 Ra, Dobaczewski & Engel, PRL94 (2005) NB: Must include quadrupole term in Schiff operator: See C.-P. Liu et al, nucl-th/0601025 7
EDM Measurement B E B μ, s E s B E d, s hf = 2μB + + 2dE hf = 2μ B 2 de s Parameters -------------------- B = 10 mgauss f = 11 Hz E = 100 kv/cm f + -f - = 10 nhz d = 1 x 10-28 e cm 8
Expected Statistical Accuracy No. of Ra atoms: 10 mci source = 3.6 x 10 8 Ra/s N = 1 x 10 7 atoms Trap storage time = 300 s E = 100 kv/cm T = 100 days Detection efficiency = 0.05 Best experimental limit: M. C. Romalis et al, PRL 86 (2001) 2505 Enhancement factor: Ra/Hg = 375 9
Search for EDM of 225 Ra Advantages of an EDM measurement on 225 Ra 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 225 Ra atoms. Small sample in an XHV allows a high electric field (> 100 kv/cm). 10 mci 225 Ra sample Magneto-Optical Trap Atomic Beam Proposed setup Oven 225 Ra Nuclear Spin = ½ Electronic Spin = 0 t 1/2 = 15 days Transverse Cooling EDM-probing region Fiber-Laser Optical Dipole Trap 10
5.5 ns 7p 1 P 1 38 ms 6d 1 D 2 100 9e- 2 2e-5 5e-7 1 Laser-cooling: 714 nm Radium Atom Energy Level Diagram 7p 3 P 2 422 ns* 7p 3 P 1 7p 3 P 0 Repump: 1428 nm 1e-1 1e-9 6e-5 9e-4 6d 5e-2 3 D 3 Dzuba et al., PRA 61, 062509 (2000) 2e-2 6d 3 D 2 4e-3 600 μs? 6d 3 D 1 1e-1 Laser-cooling on 1 S 0-3 P 1 : ~2x10 4 cycling transitions 422 ns lifetime* Accel ~ 3000 m/s 2 1 G/cm MOT gradient k B T= h/(2τ) ~ 10 μk 7 ms cooling w/o repump Repump on 3 D 1-1 P 1 : 8 s cooling w/ repump Transition frequency? Isotope shift? Hyperfine splitting? 7s 2 1 S 0 *N. D. Scielzo et al., PRA 73, 010501 (2006) 11
Argonne National Laboratory Radium EDM Experiment 12
225 Ra Source 229 Th 7300 yr α 225 Ra 15 days β 225 Ac 10 days α Fr, At, Rn ~ 4 hours α,β 209 Bi stable 10 mci 229 Th source produces 4 x 10 8 s -1 225 Ra Test source: 0.5 mci 229 Th Chemical extraction of Ra from Th Reduction of Ra(NO 3 ) 2 with Ba, Al, Ti Exotic Beam Facility ~ 1 Ci 229 Th Expected yield for 225 Ra: 3 x 10 10 s -1 13
Counts 225 Ra from the Oven 1000 3 2 7 6 5 4 13 October 03 experiment Window Facing Oven Aperture Unused Window 137 Cs 225 Ra 30% 70% γ 225 Ac β t 1/2 =14.9 d 225 Ra 40 kev γ-ray α 3 2 α 221 Fr 20 30 40 Energy (kev) 50 12% γ 218 kev γ-ray Counts 1000 6 4 100 6 4 10 2 2 2 200 221 Fr 213 Bi 137 Cs 300 400 500 Energy (kev) 600 700 26% 217 At γ 213 Po α α 213 Bi 441 kev γ-ray α 14
Spectroscopy and lifetime measurement ~250-500 ns ~1200+-100 ns * 714.3 nm 1 7p 3 P 1 6e-5 PMT 791.1 nm 6p 3 P 1 1 1 0.3 5d 3 D 2 7s 21 S 0 Radium 6d 3 D 1 6s 21 S 0 Barium 5d 3 D 1 250 μci ~ 5 nano-g 225 Ra + 100 mg Ba Notch filter *H. Bucka et al., Ann. Physik 8, 329 (1961) Transverse laser beam Ba and Ra atomic beam Oven @ 700 C 15
225 Ra Spectroscopy Fluorescence 1 S 0 F=1/2> -> 3 P 1 F=3/2> 13999.267(1) cm -1 Iodine signal Laser locking transition 13999.23 13999.25 13999.27 Wavenumber (cm -1 ) 16
Ra 7s7p 3 P 1 lifetime measurement Lifetime measurement cycle: Fluorescence Excitation laser Fluorescence τ = 422 ns +- 20 ns N. D. Scielzo et al., PRA (2006) 0 0 500 1000 1500 2000 Time (ns) 17
2500 Repump transition in 226 Ra beam 1 P1-1 S 0 photon counts 2000 1500 1000 3 D 1 -> 1 P 1 6999.83(1) cm -1 (1428.606 nm) 1 P 1 1 S 0 3 P 1 3 D 1 500 0 6999.83 6999.84 6999.85 Wavenumber (cm -1 ) 18
Radium slower and trap 750 nci 226 Ra (600 nano-g) 1 mci 225 Ra (20 nano-g) Transverse cooling 1 μs Zeeman slower MOT Repump Probe phase ~50 ms Slower, Trans cooling, MOT phase ~400 ms PMT Slower 19
Laser-Trapping of Radium Atoms World s first laser trap of radium atoms: both 225 Ra and 226 Ra atoms are cooled and trapped! Key 225 Ra frequencies, lifetimes measured. 20
Laser-Trapping of Radium Atoms World s first laser trap of radium atoms: both 225 Ra and 226 Ra atoms are cooled and trapped! Key 225 Ra frequencies, lifetimes measured. 21
Overall Trap Efficiency 225 Ra sample Magneto-Optical Trap Atomic Beam Oven Transverse Cooling 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 23
Optical Dipole Trap Intensity 1 H = de % = αe 4 Excitation rate ~ Trap potential ~ ( f f ) 2 ( f f ) laser atom 2 0 Intensity laser atom 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 24
EDM Measurement 7p 3 P 1 F = 1/2 Fluorescence 7s 21 S 0 F = 1/2 m F = -1/2 σ - m F = -1/2 m F = +1/2 σ + Excitation m F = +1/2 1. Polarize 2. π / 2 pulse 3. Free precess 4. π / 2 pulse 5. Measure population Polarizing and probing laser beam Dipole trap beam Pol. P P P + P + + E down E up B E E field plates f drive -f atom 25
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2003 Establish Ra lab, prepare Ra oven and beam 2004 Stabilize laser and perform laser spectroscopy of 225 Ra, improve oven 2005 Establish MOT of Ra atoms 2006 Establish optical dipole trap 2007 Begin EDM experiment 2008 - Improve statistics and systematics 2009 - Milestones 27
Summary New initiative at Argonne to search for the EDM of 225 Ra 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. 28
Desperate Trappers 29
Argonne http://www-mep.phy.anl.gov 30
The End 31