The Search for the Electron Electric Dipole Moment at JILA

Transcription

1 The Search for the Electron Electric Dipole Moment at JILA Laura Sinclair Aaron Leanhardt, Huanqian Loh, Russell Stutz, Eric Cornell Theory Support: Edmund Meyer and John Bohn June 11, 2008 Funding: NSF and Keck Foundation

2 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

3 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

4 Why Look for the electron EDM? The presence of an electron EDM corresponds to a Fundamental Symmetry Violation Direct T-violation [and P-violation]. CPT Theorem: T-violation CPviolation S d + _ t t + _ r r _ + S d S d

5 Test of Physics Beyond the Standard Model de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] SUSY Left Right Multi Higgs ( χ ( d ε 1 10 e cm Supersymmetry: e e 26 ) e cm ( ) 27 ( ) d ε tan β 1 k 5 10 e cm Multi Higgs: e H How well can we constrain extensions to the standard model? Left Right: d e 34 Standard Model: Std. Mod. de [e*cm] 28 ) d e e cm S.M. Barr, Int. J. Mod. Phys. A 8, 209 (1993)

6 Measuring an Electron EDM _ + S de RF B S de + _ photon µ B ν rf

7 Measuring an Electron EDM _ + E S de RF B S de + _ photon µ B ν rf

8 Measuring an Electron EDM _ + E E S de RF B S de + _ photon 2deEeff µ B ν rf

9 How Do We Lower the Limit? de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] limit on SUSY Left Right Multi Higgs E 2deEeff 10 Want BIG Electric Field! de < 2 Eeff τ N Energy splitting: 2deEeff 34 Std. Mod. de [e*cm] 28 E

10 How Do We Lower the Limit? de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] limit on SUSY Left Right Multi Higgs E 2deE de < 2 Eeff τ N Linewidth: 1/ τ Std. Mod. de [e*cm] 28 E Long Coherence Time Narrow Resonances

11 How Do We Lower the Limit? de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] limit on SUSY Left Right Multi Higgs E N 2deE Want Large Count Rates de < 2 Eeff τ N How well split the resonance: Std. Mod. de [e*cm] 28 E

12 How Do We Lower the Limit? de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] SUSY Left Right Multi Higgs limit on de < 2 Eeff τ N Three considerations for a good eedm experiment: Energy splitting: 2deEeff Linewidth: 1/τ Std. Mod. de [e*cm] 28 How well split the resonance: N

13 Current limit, beam of atomic Thallium: B. Regan, E. Commins, C. Schmidt, D. DeMille, Phys. Rev. Lett. 88, (2002) de < 1.6 x e*cm (90% c.l.) Eeff Commins Tl beam 6 x 107 V/cm Hinds YbF beam > > > DeMille PbO vapor cell DeMille, Doyle, Gabrielse, ThO beam Weiss trapped Cs Heinzen trapped Cs Gould Cs fountain Shafer Ray PbF beam Cornell trapped HfF+ or ThF+ < < < > > τ 2 msec N eff 109 s 1 < < > > > > < < < < <<

14 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

15 Why Use Molecules? Greater internal electric fields factor of 103 over atoms Closely spaced levels of opposite parity Easy to polarize (~10V/cm) Systematic Checks

16 Why Use Molecules? Greater internal electric fields factor of 103 over atoms Closely spaced levels of opposite parity Easy to polarize (~10V/cm) Systematic Checks Why Use Ions? Ions are easy to trap Trapped molecular ions allow for long coherence times

17 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

18 Intramolecular Electric Fields Use the J=1, 3 1 state of HfF+ Small Ω doublet splitting makes it easy to polarize For now, ignore hyperfine splitting E =0 eff m=1 m=0 m= +1 ~ 1 MHz Budker, DeMille

19 Intramolecular Electric Fields Elab mixes states of opposite parity inducing a net molecular dipole moment in the lab frame. Sign of Eeff is set by sign of induced molecular dipole moment. Eeff > 0 Eeff Eeff µ elela µ elela b b Elab m=1 µ elela b Eeff < 0 Eeff m=0 m= +1 ~ 1 MHz µ elela b Eeff

20 Intramolecular Electric Fields Elab mixes states of opposite parity inducing a net molecular dipole moment in the lab frame. Sign of Eeff is set by sign of induced molecular dipole moment. If de 0, shift of magnitude deeeff 2d ee eff Eeff > 0 Eeff Elab Eeff m=1 m=0 2de E e Eeff < 0 Eeff m= +1 ~ 1 MHz ff Eeff

21 Intramolecular Electric Fields Elab mixes states of opposite parity inducing a net molecular dipole moment in the lab frame. Sign of Eeff is set by sign of induced molecular dipole moment. If de 0, shift of magnitude deeeff Small magnetic field B causes Zeeman shift and biases signal off of zero B+ 2µ E e ff e d 2 Eeff > 0 B Eeff m=1 B Elab m=0 Eeff m= +1 ~ 1 MHz E ff - 2d e e B 2µ B Eeff < 0 Eeff Eeff

22 Systematic Checks Vary magnitude of Elab: Linear Stark shift implies fully mixed states of opposite parity and Eeff nominally independent of Elab. Eeff > 0 B+ 2µ E e ff e d 2 B Eeff m=1 B Elab Eeff < 0 m=0 E ff - 2d e e B 2µ B Eeff Eeff m= +1 ~ 1 MHz

23 Systematic Checks Vary magnitude of Elab: Linear Stark shift implies fully mixed states of opposite parity and Eeff nominally independent of Elab. Co-magnetometer: Zeeman shift is common mode. Difference between Zeeman splittings ν =4deEeff. Eeff > 0 B+ 2µ E e ff e d 2 B Eeff m=1 B Elab Eeff < 0 m=0 E ff - 2d e e B 2µ B Eeff Eeff m= +1 ~ 1 MHz

24 Systematic Checks Vary magnitude of Elab: Linear Stark shift implies fully mixed states of opposite parity and Eeff nominally independent of Elab. Co-magnetometer: Zeeman shift is common mode. Chop both B and Elab. Eeff > 0 2µ B B - 2d E e ef f ν B - ν m=1 B Elab Eeff < 0 Eeff Eeff B =4deEeff m=0 m= +1 2µ B 2d B + ee e ff Eeff ν B - ν B =4deEeff ~ 1 MHz

25 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

26 Applying Electric Fields Neutral Molecule Beam Experiment Elab

27 Applying Electric Fields Neutral Molecule Experiment Elab The Problem with Parallel Plates for Molecular Ions Elab +

28 Rotating Electric Fields Elab (t ) Elab [ cos(ωt ) xˆ + sin(ωt ) yˆ ] ω slow enough quantization access can track with it, dmolelab > ω ω large enough that radius of micromotion smaller than trap size Elab ~ 10 V/cm ω ~ 400 khz

29 Proposed Experimental Procedure Load ions into one spin state: Raman π pulse Electron Spin Resonance: Ramsey π /2 pulse Coherent Evolution Ramsey π /2 pulse Read out relative spin populations: Raman π pulse Photodissociation of HfF+ Hf+ + F Separately detect Hf+ and HfF+

30 Test of Physics Beyond the Standard Model de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] de < e*cm / day1/2 SUSY Left Right Multi Higgs de < 2 Eeff τ N Projected sensitivity: de < e*cm / day1/2 Theoretical calculations: Eeff ~ 9 x 1010 V/cm [1] Expected spin coherence time: τ ~ 100 ms Expected counting statistics: N ~ 9 x 106 ions / day Std. Mod. de [e*cm] [1] Theory: E.R. Meyer, J.L. Bohn, and M.P. Deskevich Phys. Rev. A 73, (2006), E.R. Meyer private communications, Petrov et al. Phys. Rev. A 76, 1-4 (2007)

31 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

32 Candidate Molecules: HfF+ and ThF+ Molecule Requirements Large internal electric fields (Eeff) Easy to polarize State molecules 3 [1] Contains one heavy atom Ground state or long lived metastable state needed for long coherence times Small magnetic moment HfF+ Eeff: ~ 30 GeV/cm [2] ~ 24 GeV/cm [3] ~1 V/cm to polarize ThF+ Eeff: ~ 90 GeV/cm [2] [1] E.R. Meyer, J.L. Bohn, and M.P. Deskevich Phys. Rev. A 73, (2006) [2] E.R. Meyer private communications [3] Petrov et al. Phys. Rev. A 76, 1-4 (2007)

33 HfF+ and ThF+ Spectroscopy No EXPERIMENTAL DATA about internal structure of either molecule Theoretical Predictions for HfF+ 1 Structure Π 1 for ThF+ Structure cm cm-1 Π2 Π1 3 Π0+ 3 Π0 3 Theoretical Predictions cm cm cm cm cm-1 3 Σ cm cm-1 3 HfF+ Theory from: 1599 cm-1 Petrov et al. Phys. Rev. A 76, 1 4 (2007) ThF+ Theory from: E.R. Meyer, private communications

34 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

35 Current Experimental Progress Not to Scale 1064 nm ablation pulse pulse valve skimmer dye laser ~700 nm VRF cos(ωt) ~ 100 psig He Hf rod + 1% SF6 Laser Ablation in a Supersonic Jet photomultiplier tube Fluorescence Spectroscopy Creation of HfF+,ThF+ Measure rotational temperature of neutral Cooling of rotational, HfF molecular beam vibrational and translational motion VRF cos(ωt) VRF cos(ωt) VRF cos(ωt) RF Paul Trap Mass Spectrometry Trap Hf+, HfF+, HfF2+, HfF3+, Th+, ThF+, ThF2+,ThF3+ microchannel plate Ion Beam Imaging Measure translational temperature of ion beam

36 Molecular Ion Production and Trapping VRF cos(ωt) VRF cos(ωt) VRF cos(ωt) VRF cos(ωt) 20 cm ion signal [arb. units] RF Paul Trap and Quadrupole Mass Filter ThF3+ ThF Th+ ThF mass [amu]

37 1 amu Mass Resolution for Time of Flight Mass Spectrometry Arrival Time Data from 2-photon REMPI from HfF X2 180 HfF+ 179 HfF+ 178 HfF+ 177 HfF+ 176 HfF+ Wavenumber [cm-1] 3/2

38 Characterizing Temperatures Only get to use molecules in one electronic, vibrational and rotational state for measurement Decoherence depends on temperature Too hot Ions see inhomogeneous fields As temperature decreases Ion-Ion collision rate increases Ions not in the right state can still collide leading to decoherence

39 Supersonic Expansion and Translational Cooling N = 600 ions/shot T=2K

40 LIF of neutral HfF Evidence for low rotational temperatures [14.2] Ω =3/2 J =9/2 J =7/2 J =5/2 J =3/2 v =2 v =1 v =0 3 transitions per J level. Count lines to measure rotational temperature. Experiment & Theory T~5 K X 2 3/2 J =11/2 v =2 v =1 v =0 J =9/2 J =7/2 J =5/2 J =3/2 T=5 K

41 Neutral HfF states observed via 2 photon ionization also show low rotational temperatures Data Model Ω"=3/2 Ω'=3/2 T=8cm 1, B"=0.284cm 1, B'=0.264cm HfF signal (arb units) Laser energy (cm ) cm 1 2 4

42 Outline Motivation Why Use Molecular Ions to measure the electron EDM? Intramolecular Fields Proposed Experimental Procedure What Molecule to Use? Current Experimental Results Rethinking Ion Production Conclusions

43 Rethinking Ion Trap Loading Create pre-polarized sample of ions via 2 photon process 1064 nm ablation pulse pulse valve 2 photon ionization deflection plate skimmer VRF cos(ωt) + VRF cos(ωt) + ~ 100 psig He + 1% SF6 Hf rod VRF cos(ωt) VRF cos(ωt) + + Total length ~1.5 m microchann el plate Not to Scale

44 Current Experiment Status Created and Trapped HfF+ and ThF+ Mass resolution to distinguish 1 amu differences Characterized supersonic expansion and beam Internal and External temperatures in the right range for final experiment Theoretical considerations of Berry s phase and decoherence effects o Ongoing survey spectroscopy of HfF+ and ThF+ o Ongoing development of methods for loading trap with ions pre-polarized o Spin level readout and characterization of coherence times o On to measurement of the electron EDM

45 Test of Physics Beyond the Standard Model de < 1.6 x e*cm [~10 18 Debye] E.D. Commins Tl Exp. Limit [PRL 88, (2002)] de < e*cm / day1/2 SUSY Left Right Multi Higgs Std. Mod. de [e*cm] Projected sensitivity: de < e*cm / day1/2 Theoretical calculations: Eeff ~ 9 x 1010 V/cm Expected spin coherence time: τ ~ 100 ms Expected counting statistics: N ~ 9 x 106 ions / day