Electric Dipole Moments PPAP community meeting 2015 Ben Sauer

A search for new physics. EDMs of fundamental particles violate P and T symmetry. Search for physics beyond the Standard Model (probes physics at many TeV). T-violation = CP-violation (via CPT). CP-violation is a big mystery in particle physics / cosmology.

CP from fields to particles to atoms YbF, Cs ThO*, HfF+ atom/molecule level Higgs SUSY Left/Right T-weak Strong CP field theory CP model qGG electron/quark level de, Cs dq dcq muon? nuclear level NNNN Schiff moment n, p nucleon level Hg TlF ~

Neutron EDM nEDM UK is back in business! After years in the cryogenic wilderness... nEDM UK is back in business! New systematic effect identified, confirmed New diagnostic tool developed Revised nEDM world limit Major players in PSI-nEDM... ... which is now taking world-beating data Publications!

Revised nEDM world limit Further work (almost entirely by Sussex group) based on data used for 2006 limit: Inclusion of new gravitation depolarization systematic Inclusion of new information from subsequent measurements of apparatus components Much improved calculation of spectrum, based on detailed Monte Carlo Inclusion of new measurement of n to Hg gyromagnetic ratio & updated Hg EDM limit Most comprehensive & detailed nEDM analysis ever http://arxiv.org/abs/1509.04411 submitted to PRD Results in slight revision of limit: 2.9 3.0x10-26 e.cm Scale of false EDM effect previously had to be adjusted to fit data – now (with grav depol) matches predictions well!

nEDM at PSI - www.neutronedm.org nEDM now running with world-beating sensitivity of ~1.5x10-25 e.cm/day Sussex taking leading role: 3He magnetometry work Systematics, simulation, analysis Robust backup to (unreliable) HV supply Devised & coordinated data blinding Harris appointed Chair of Collaboration Board Blinded data-taking began Sept 13th 2015; should exceed previous limit mid-2016

n2EDM at PSI Planned upgrade: Double Ramsey chamber system – measure both E-field directions at once Unprecedented systematics control Geometry better matched to source: more neutrons Magnetometry confined to ground planes; can increase HV Much improved magnetic shielding Should achieve sensitivity ~3Ex10-27 e.cm SoI planned to be submitted in 2016; complete construction by 2020 this will ensure we stay ahead of competition

Competition: SNS nEDM at ORNL Cryogenic storage of neutrons Experiment in Critical Component Demonstration phase. Data collection planned to start 2021

Proton EDM Limit from 1989 TlF experiment: 6x10-23 e.cm Limit from Hg: 5x10-24 e.cm A Storage Ring Experiment to detect a Proton Electric Dipole Moment arxiv.org: 1502.04317v1 Proposal to directly measure pEDM in a storage ring Work at ‘magic’ velocity at which spin precession matches momentum in ring (0.7 GeV/c) Aim is to reach 10-29 e.cm level

eEDM using YbF YbF (or ThO*, or HfF+) molecule acts as amplifier for eEDM © Jony Hudson

“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 Johnson noise from electric field plates would limit sensitivity (moving to thin-film electrodes) Two orders of magnitude improvement is underway, aiming for 3x10-29 e.cm We have a lot of experience and a sophisticated data analysis scheme, so should be able to control systematic effects.

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

Current status of EDMs d(muon) < 1.9×10-19 d(proton) < 5×10-24 d [e.cm] d(muon) < 1.9×10-19 neutron: 10-20 electron: 10-22 Left-Right MSSM Higgs Multi d(proton) < 5×10-24 10-24 d(neutron) < 3×10-26 YbF 10-26 10-28 d(electron) < 9×10-29 ThO 10-29 1960 1970 1980 1990 2000 2010 2020 2030

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

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

An EDM experiment E Precess time T Analyze Polarize

New systematic: Gravitational depolarisation & “Ramsey wrapping” Average B field sampled depends on neutron energy Low-energy tail gives asymmetric distribution of accumulated Ramsey phase Ramsey frequency measurement is modulo 2p, so low tail can end up on high end of distribution! “Ramsey wrapping” Causes nonlinearities in frequency response, depolarisation etc Predicted in calculations by Sussex group in 2013 Now verified by comparison with data: http://arxiv.org/abs/1506.06563, publication imminent in PRD Affects sytematic correction in nEDM analysis! motional false edm signal vs. n/Hg frequency ratio offset Polarization vs. dB/dz Without grav. depol. With grav. depol.

UCN spin-echo: New diagnostic tool Flip spins part way through Ramsey sequence. Spins that are “ahead” are sent to the back & vice-versa, to cancel dephasing. Changing pulse timing allows determination of neutron spectrum and B-field gradient offset. Idea developed at PSI; Sussex group provided underlying analytic calculations & simulations of depolarisation processes http://arxiv.org/abs/1506.00446 - publication imminent in PRL (“Editor’s Choice” article) We can now measure the neutron spectrum directly!