Future electron EDM measurements using YbF Ben Sauer

Recent electron EDM measurements 10-22 Tl experiment (2002) de < 1.6 x 10-27 e.cm (90% c.l.) 10-24 MSSM f ~ 1 YbF experiment (2011) de < 1 x 10-27 e.cm (90% c.l.) 10-26 Multi Higgs Left -Right MSSM f ~ a/p 10-28 ThO* experiment (2013) de < 8.7 x 10-29 e.cm (90% c.l.) Predicted values for the electron edm de (e.cm) 10-30 10-32 10-34 10-36 Standard Model

An EDM experiment E Precess time T Analyze Polarize

Sensitivity of an EDM experiment Uncertainty: size of E field coherence time number of molecules polarization contrast

Why polar molecules? -hde E• hde  E Interaction energy Analogous to magnetic dipole interaction -gem B.s but violates P&T hde  E Factor h includes both relativistic interaction Z3, and polarization electric field system containing electron © Imperial College London

YbF: really large internal field Parpia Quiney Kozlov Titov 18 GV/cm 15 GV/cm (2011) 15 Effective Field |hE| (GV/cm) 10 5 5 10 15 20 25 30 Applied Electric Field (kV/cm) © Imperial College London

ThO*: huge internal field Effective field Eeff in YbF is 26 GV/cm when molecule is fully polarized For ThO* Eeff is about 84 GV/cm (factor of 3.2 more sensitive) Mostly relativistic: (also depends on structure) ThO* can be fully polarized!

Comparing some atomic and molecular systems YbF, 2011: |Eeff|= 14.5 GV/cm (h = 0.56) |de|<1.0 x 10-27 e.cm (90% c.l.) Tl, 2002: |Eeff|= 72 MV/cm (Eeff = -582 Eapplied) |de|<1.6 x 10-27 e.cm (90% c.l.) PbO*, 2013: |Eeff|= 25 GV/cm |de|<1.7 x 10-26 e.cm (90% c.l.) Eu0.5Ba0.5TiO3, 2012: |de|<6 x 10-25 e.cm (90% c.l.) ThO*: |Eeff| = 84 GV/cm (factor of 6 on 2011 YbF) |de|<8.7 x 10-29 e.cm (90% c.l.)

Upgrades since 2011 In total, a factor of 3 in sensitivity 3rd layer of magnetic shield (less noise) Longer inner magnetic shield (reduce end effects) Separate rf, high-voltage plates (reduce end effects, higher voltage, less leakage) 1kW/1ms rf pulses (reduce gradient effects from both movement and linewidth) Longer interaction region In total, a factor of 3 in sensitivity

Our plans for YbF More molecules - increase beam intensity - better detection Slower molecules Made possible by new technology - solid state lasers - buffer gas beam sources

© Jony Hudson

A rough guide to YbF 552nm A 2P½ (v=0, N=0) F = 1 170MHz mF = -1 mF = 0 mF = +1 170MHz X 2S+ (v=0, N=0) F = 0 mF = 0

YbF eEDM measurement Measure population in F = 0 E, B Precess Polarize time T Analyze Measure population in F = 0

Signal vs. magnetic phase F=0 population F = 1 © Jony Hudson F = 0

Scheme increases population by a factor of 7, sensitivity by 2.6 More molecules: Initial pumping Use cycling transition to optically pump molecules into ground rotational state. (-) F=0, 1 A2P1/2 (v=0, J=1/2) Optical pumping (N=2 rotational state) F=2+ Scheme increases population by a factor of 7, sensitivity by 2.6 F=1 N=2 (J=3/2, 5/2) (+) F=3 F=2- F=1+ rf mixing (~100 MHz) N=1 (-) F=2 Microwave mixing (14 GHz) F=0 F=1- F=1 N=0 (+) F=0

More molecules: Better detection Fluorescence detection is only about 0.7% efficient Probe laser beam

More molecules: make them cycle F=0 F=0, 1 A2P1/2 (v=0, J=1/2) F=1 F=1+ F=1- F=2 F=2+ F=2- F=3 N=0 (+) N=1 (-) N=2 (J=3/2) (+) (-) Molecules cycle until they escape to v=1 vibrational state (14 photons/molecule)

F = 0 and F = 1 are the two output ports of the interferometer A flaw: measuring the eEDM F = 0 F = 1 Detector count rate F = 0 and F = 1 are the two output ports of the interferometer -B0 B0 Applied magnetic field

Shelve population in N=1 (-) F=0, 1 A2P1/2 (v=0, J=1/2) Sensitivity gain of 5 F=2+ F=1 N=2 (J=3/2) (+) F=3 F=2- F=1+ N=1 (-) F=2 F=0 F=1- F=1 N=0 (+) F=0

High fidelity shelving The problem is the YbF beam is larger than l at 14 GHz. Cross section of simulated parallel plate transmission line. plate uniform (integrated) field plate microwaves in

High fidelity shelving Transition probability over cross section of YbF beam Average transition probability N=0 Þ N=1 over YbF beam >98%

Slow source of YbF 4K copper cell 4K helium flow Nick Bulleid (PhD thesis, 2013) YbF formed by laser ablation, cools to 4K, forward velocity is 150 m/s. Flux is similar to current beam (5x109 YbF /str/pulse)

Slow source of YbF (20 sccm) YbF signal YbF velocity (m/s) time after ablation (ms) time after ablation (ms) 2011 supersonic beam had forward velocity of 600 m/s

“Traditional” YbF eEDM Compared to 2011 measurement: Factor 3 for longer plates Factor 2 for N=2 population pumping Factor 5 for cycling detection Factor 4 for slower beam Two orders of magnitude improvement is underway. We have a lot of experience and a fairly sophisticated data analysis scheme, so should be able to control systematic effects.

Is there more? YbF eEDM experiment takes place in the ground state, so why not coherence times of 1s?

Building the YbF fountain 4K Fantastically inefficient: 10-8 from cell to detector. But T = 300ms, so 60h of data gives sd = 3x10-31 e.cm!

The YbF team Mike Tarbutt Ed Hinds Jony Hudson Joe Smallman Isabel Rabey B.E.S. Jack Devlin YbF fountain: James Bumby James Almond Jongseok Lim Noah Fitch

Everything clear?