Time Reversal and the electron electric dipole moment. Ben Sauer

Transcription

1 Time Reversal and the electron electric dipole moment Ben Sauer

2 Mysteries of physics

3 Mysteries of physics Baryon asymmetry Why is there more matter than antimatter in the observable universe?

4 Breaking P and T symmetry time reversal t -t parity r -r d e 0 breaks P & T. CPT tells us CP is broken matter/antimatter asymmetry

5 eedm limits over time 60 years of measuring zero

6 Beyond standard model and the eedm Imperial: Nature (2011), ACME: Science (2014), JILA: PRL Figure adapted from Ben Spaun, PhD Thesis, Harvard University, (2014).

7 eedm sensitivity to new physics Limits on the masses of hypothetical particles. H 0 and H ± are additional neutral or charged Higgs particles, and those with a tilde are supersymmetric partners of the standard model particles. Reproduced from Science (2017).

8 The vacuum is complicated e selectron gaugino SUSY electron edm g e 2 naturally a/p d e ~ (loop) m e L 2 sin CP scale of SUSY naturally 200GeV d e naturally about e.cm

9 An EDM experiment E Polarize Precess time T Analyze

10 CP from fields to particles to atoms field theory CP model electron/quark level muon? nucleon level nuclear level atom/molecule level Higgs SUSY Left/Right T-weak d e, C s d q n, p YbF, Cs ThO*, HfF + d c q Strong CP qgg ~ NNNN Schiff moment Hg TlF

11 Why polar molecules? E hd e Interaction energy -hd e E Analogous to magnetic dipole interaction -g e m B. but violates P&T electric field system containing electron Factor h includes both relativistic interaction Z 3, and polarization. h can be very large! Imperial College London

12 YbF Relevant levels 1,-1 1,+1 Measure the splitting of the 1, 1 and 1,1 levels in an applied electric field Vibration Rotation Hyperfine

13 YbF eedm measurement Jony Hudson

14 YbF eedm measurement E, B Polarize Precess time T Analyze 1 1 i i e e 2 2 Measure population in F = 0 2 N cos

15 The scale of the apparatus magnetic shields vacuum chamber plate structure

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17 A magnetic field scan YbF state F=1 F=0 F=1 F=0 F=1 signal cos 2 (φ B + φ E ) F=0

18 A magnetic field scan with E reversed Reverse E relative to B Looking for a shift of less than 2 µrad signal cos 2 (φ B + φ E ) signal cos 2 (φ B φ E )

19 2011 result 2011 dataset: 6194 measurements (6min/measurement) d e = 2.4 ± 5.7 stat ± 1.7 syst e. cm d e < e. cm with 90% confidence J J Hudson et al. Nature (2011) D M Kara et al. New. J. Phys (2012)

20 Sensitivity Limit Photon shot noise : σ de ħ 2E eff C τ N Agrees with final error in 2011 to within 10% Get more molecules Fixed by molecule Interaction time Contrast (do experiment better)

21 More molecules Use cycling transition to optically pump molecules into ground rotational state. (-) F=0, 1 A 2 P 1/2 (v=0, J=1/2) Scheme increases population by a factor of 7, sensitivity by 2.6 N=2 (J=3/2, 5/2) (+) N=1 (-) F=1+ F=2 F=0 F=1- F=2+ F=1 F=3 F=2- rf mixing (~100 MHz) N=0 (+) F=1 F=0 Microwave mixing (14 GHz) Optical pumping (N=2 rotational state)

22 More molecules (better detection) Fluorescence detection is only about 0.7% efficient Probe laser beam

23 An interlude on laser cooling molecules Molecules have many levels, and we need to scatter 10,000 photons. e g It seems that hundreds of repump lasers are needed.

24 Rotation: selection rules to the rescue Laser cooling molecules: Rotation Angular momentum J can only change by 0, 1. Parity of rotational state (-1) J must change from (+) ( ). J=2 (+) J=1 (-) J=0 (+) J=2 (+) Cool on J=1 J=0 transition, P(1) line. J=1 (-) J=0 (+)

25 Improved state detection scheme Instead.. Previously Then First detect F=0 F=1 1 extra laser around 552 nm with rf 3 sidebands to drive P 1 (F=1 + ), P 1 (F=2,0) P 1 (F=1 - ) MW: khz v>0 v>0 1.3 photons per molecule. With 0.6% total detection efficiency, most photons not captured Up-to 14 photons per molecule. With 0.6% total detection efficiency, still only 5% detected, but 11 times Another factor of two in signal more than before

26 New magnetic scan curves Single shot: ~1000 molecules ~ molecules Can detect both quadratures New detection scheme increases sensitivity by 11.5 = 3.4 in each detector

27 Combine quadrature detectors S A S B S A +S B Robust to source fluctuations

28 Sensitivity outlook 2011 sensitivity: Target 2 nd generation Imperial e. cm/ day 2018 (expected) sensitivity: e. cm/ day

29 Transverse cooling of YbF Probe lasers Camera 2 No Blue-detuned Red-detuned cooling applied Camera 1 Δ = +8 MHz No cooling Transverse cooling 20cm T < 50 µk nm Δ = -8 MHz YbF source Ultracold molecules for measuring the electron's electric dipole moment J. Lim, J. R. Almond, M. A. Trigatzis, J. A. Devlin, N. J. Fitch, B. E. Sauer, M. R. Tarbutt, E. A. Hinds; arxiv 1712:02868

30 Sensitivity outlook Target 3 rd generation Imperial

31 Team EDM Jack Devlin Ben Sauer Ed Hinds Chris Ho Izzie Rabey Mike Tarbutt

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33 ThO*: huge internal field Effective field E eff in YbF is 26 GV/cm when molecule is fully polarized For ThO* E eff is about 84 GV/cm (factor of 3.2 more sensitive) Mostly relativistic: Z Z 2.1 (also depends on structure) ThO* can be fully polarized! Th Yb 3 =

34 Comparing some atomic and molecular systems YbF, 2011: E eff = 14.5 GV/cm (h = 0.56) d e <1.0 x e.cm (90% c.l.) Tl, 2002: E eff = 72 MV/cm (E eff = -582 E applied ) d e <1.6 x e.cm (90% c.l.) PbO*, 2013: E eff = 25 GV/cm d e <1.7 x e.cm (90% c.l.) Eu 0.5 Ba 0.5 TiO 3, 2012: d e <6 x e.cm (90% c.l.) ThO*: E eff = 84 GV/cm (factor of 6 on 2011 YbF) d e <8.7 x e.cm (90% c.l.)