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Measuring the Electron EDM Using Ytterbium Fluoride (YbF) Molecules βmeasuring the shape of the electronβ Joe Smallman The electron electric dipole moment (EDM) β’ Displacement of centre of charge from centre of mass πΈ β β ππ β β β β β π = β ππ β πΈ π π Ηπ 2 Electron EDM estimates David A. Aguilar Harvard-Smithsonian Center for Astrophysics not enough CP violation |dethallium|< 1.6 x 10-27e.cm 3 How small is that? β’ Assume: β’ ππ β 10β27 π. ππ = 2 × 10β19 π. π0 = 5 × 10β19 π· β’ πΈ β 1πΊπ/ππ EDM interaction: βππ β πΈ β 0.25 ππ»π§ β’ β‘ βππ΅ β π΅ for β 17ππ magnetic field β’ β 10β10 ππβ1 β’ β 10β18 ππ 4 How atoms and molecules can help β’ Amplify the electron EDM interaction! βπ π β πΈ ππ complicated special relativity βππ β πΈeff πΈeff = πΈeff max Ξ· πΈapp π§ π πΈapp π§ structure dependent factor ~π 3 polarisation factor πβπ§ 5 YbF electric field enhancement β’ πΈeff = 14.5 GV/cm for πΈapp = 10 kV/cm β’ Enhancement of 106 ! β’ Needs βonlyβ nano-Gauss level of B-field control 6 YbF energy levels 7 EDM measurement πΈeff Torque: dπΉ = πe × πΈπππ + (π × π΅) dt πΉ π΅ (ΞΌB β de Eeff )T Ο= Δ§ βπ < 7 ΞΌrad or βπ < 2 mHz 8 Measuring the electron EDM 9 Interference fringes π= cos2 Ο Ο= (ΞΌB β de Eeff )T Δ§ 10 Lots of other parameter modulations demonstrated in last slide β’ E-field direction β’ B-field direction β’ B-field magnitude β’ rf pulse frequency (independently) β’ rf pulse amplitude (independently) β’ rf pulse phase difference β’ laser frequency 11 Result β’ 2011 dataset: 6194 measurements (6min/measurement) de = β2.4 ± 5.7stat ± 1.7syst × 10β28 e. cm de < 1 × 10β27 e. cm with 90% confidence J J Hudson et al. Nature 473 493-496 (2011) D M Kara etal. New. J. Phys. 14 103051 (2012) 12 Upgrades since 2011 β’ 3rd layer of magnetic shielding β’ Less magnetic field noise β’ Longer inner magnetic shield β’ Reduce end effects β’ Separate rf transmission line from HV plates β’ Reduce end effects, higher applied E-field, less leakage old scheme new scheme β’ Shorten rf pulses β’ Reduce systematics associated with rf detuning 13 YbF fountain β’ 0.5s coherence time instead of 0.5ms ο 6 × 10β31 e cm in 8hrs Tarbutt et al. New J. Phys. 15 053034 (2013) 14 The YbF eEDM team Joe Smallman Ben Sauer Jack Devlin Mike Tarbutt Ed Hinds Jony Hudson 15 EDM measurement β’ Measure the EDM induced splitting nuclear spin electron spin +ππ πΈeff mF=-1 large tensor Stark shift -ππ πΈeff mF=0 F=1 mF=+1 F=0 mF=0 16
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