Search for a Permanent Electric Dipole Moment in Ra EDM Spin EDM Spin EDM. Spin. Pseudo-scalar. s d

Transcription

1 Search for a Permanent Electric Dipole Moment in Ra T + P EDM Spin EDM Spin EDM Spin Pseudo-scalar s d

2 C. S. Wu Parity (space reversal) x, y, z -x, -y, -z z y Parity z x x y Pseudo-scalar (x y) z s p

3 C. N. Yang T. D. Lee

4 Discrete Fundamental Symmetries P C T Parity, or Spatial Inversion Charge conjugation, or particle antiparticle symmetry Time reversal CP CPT Exact symmetry in quantum field theory with Lorentz invariance

5 James W. Cronin Neutral K mesons Particles of definite CP Allowed decay mode K even ππ K odd πππ K odd ππ at the level of 0.2%!!!

6 P violation and CP violation in the Standard Model Parity Violation Weak interaction coupling via (Vector Axial Vector) CP Violation Cabbibo-Kobayashi-Maskawa Matrix

7 More CP-Violation Mechanisms? Strong CP problem CP-violating phase in Quantum Chromodynamics Supersymmetry More particles More CP-violating phases Matter-antimatter asymmetry Require additional CP-violation mechanism(s)

8 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 Diamagnetic Atoms (Hg, Ra) Paramagnetic Atoms (Tl) Molecules (PbO) Quark EDM Quark Chromo-EDM Electron EDM Physics beyond the Standard Model: SUSY, String

9 Measurability of Nuclear EDM L.I. Schiff, Phys. Rev. (1963) Schiff shielding d% atom = d nucleus d = d% + d = atom atom nucleus 0 Incomplete cancellation d = d% + d atom atom nucleus 1) nucleus has finite size; 2) charge distribution EDM distribution. Schiff moment (toy model) r r d d 10 d c d 5 atom nucleus nucleus ratom 2 2 nucleus d c ( ) S d r r d S r r 1 1 atom atom c 0 Nuclear Schiff moment is lowest order, P,T-odd, measurable electric moment. r S = e 10 p ( r 2 p 5 r 2 ) 3 ch r r p a radially-weighted dipole moment

10 EDM Measurement B E s hf = 2μB + + 2dE hf = 2μ B 2 de B E s Parameters B = 10 mgauss f = 11 Hz E = 100 kv/cm f + -f - = 10 nhz d = e cm

11 Optical Pumping 1 P 1 F = 1/2 m F = -1/2 m F = +1/2 Decay σ + Excitation 1 S 0 F = 1/2 m F = -1/2 m F = +1/2

12 Fortson Hg-199 slide Courtesy of Mike Romalis

13 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* SkO Schiff moment of 199 Hg, de Jesus & Engel, PRC72 (2005) Schiff moment of 225 Ra, Dobaczewski & Engel, PRL94 (2005)

14 Search for Electric Dipole Moment of 225 Ra Advantages of an EDM measurement on 225 Ra atoms in a trap EDM enhanced by ~ due to nuclear octupole deformation. Trap allows the efficient use of the rare and radioactive 225 Ra atoms. Long coherence time (~ 100 s), negligible v x E systematics, high electric field (100 kv/cm). Proposed setup 225 Ra 10 mci 225 Ra sample Magneto-Optical Trap Atomic Beam Nuclear Spin = ½ Electronic Spin = 0 t 1/2 = 15 days Oven Transverse Cooling EDM-probing region Our sensitivity goal: 1 x e-cm. d( 199 Hg) < 2 x e-cm (95% C.L.) Romalis et al., PRL86 (2001) Ra / Hg Enhancement factor ~ Optical Dipole Trap

15 225 Ra Source 229Th 7300 yr α 225Ra 15 days β 225Ac 10 days α Fr, At, Rn ~ 4 hours α,β 209Bi stable 1 mci 229 Th source produces s Ra Chemical extraction of Ra from Th Reduction of Ra(NO 3 ) 2 with Ba, Al, Ti RIA ~ 1 Ci 229 Th Expected yield for 225 Ra: s -1

16 6 ns 7p 1 P 1 1e-1 Radium Atom Energy Level Diagram Dzuba et al., PRA 61, (2000) 0.8 ms δv / γ = 2.5 mm/s 6d 1 D 2 2e-6 Cycling rate ~ 1 MHz MOT lifetime ~ 20 s 5e-4 7p 3 P 2 5e-2 6d 3 D 3 2e-2 5e ns 7p 3 P 1 7e-10 2e-2 6d 3 D 2 1 4e-5 2e μs 7p 3 P 0 6e-4 6d 3 D 1 Linewidth ~ 400 khz * Without repump, cycles. * With repump at 1428 nm, cycles. Cooling 7 μk, 14 mm/s B gradient ~ 1 G / cm 7s 21 S 0

17 Laser-Trapping of 225 Ra and 226 Ra Atoms Key 225 Ra frequencies, lifetimes measured Scielzo et al. PRA (2006) 225 Ra laser cooled and trapped! Guest et al. PRL (2007) 1 P 1 Repump 3 P 1 3 D 1 Laser-cooling Ra atom trap! 1 S 0 100x Ra atomic beam

18 Oven: 225 Ra EDM measurement on 225 Ra Transverse cooling Zeeman Slower Magneto-optical trap Statistical uncertainty: 100 days 100 kv/cm 100 s 10% δd = e cm Optical dipole trap EDM measurement Ra / Hg Enhancement factor ~ Best experimental limit: d( 199 Hg) < e cm

19 Nuclear EDM Searches Isotope Current Limit Institution Technique (e cm) Neutron < 2.9E-26 SNS Superfluid He Grenoble Grenoble 199 Hg < 2.1E-28 Washington 129 Xe (0.7 ± 3.3)E-27 Michigan Washington Princeton 4 cells Liquid cell 225 Ra N/A Argonne KVI 223 Rn N/A Michigan & TRIUMF Trap Cell 2 H N/A Brookhaven Storage ring

20 Radium EDM Collaboration Irshad Ahmad Kevin Bailey Michael Bishof Jeff Guest John Greene Harvey Gould Roy Holt Zheng-Tian Lu Peter Mueller Tom O Connor Ibrahim Sulai Will Trimble Argonne Atom Trappers