EDM Experiments: UK interests Philip Harris PPAP meeting 22nd July 2014

Electric Dipole Moments + EDMs are P, T odd Complementary study of CPv: must test elsewhere than K, B Strong CP problem Constrains models of new physics SUSY CP problem Baryon asymmetry SM CPv inadequate New models bring larger EDMs Clean system – background free n g p p  × q g gaugino squark

LHC and SUSY LHC excludes NP scenarios 100 GeV-1 TeV This solves “old” SUSY-CP problem of EDM constraints on CPv phases by raising MSUSY, but moves away from “naturalness” argument that msquark should be near to weak scale High mH also makes NMSSM models interesting. These often have EDMs at 2 loops... Constraints already tight; limit CP-odd H decays. Still need viable baryogenesis mechanism. Essential to look at other CPv channels See e.g. McKeen, Pospelov, Ritz, http://uk.arxiv.org/pdf/1303.1172

nEDM History Factor 10 per decade on average ... but slowing

Sensitivity a <= 1 T <= few hundred s E can be high in strong dielectric – LHe N high in superthermal (LHe) source Universal agreement that ultimate sensitivity will almost certainly come from a cryogenic experiment.

CryoEDM 10-year effort But... Demonstrated superthermal n production at expected rate Up to 65% polarisation, clear path for improvement Transport to cells, and from cells to detector E-field same as RT-edm; clear path forward to increase substantially Proof-of-principle effective superconducting magnetic shielding Reliable operation of solid-state detectors in LHe Development of SQUID magnetometry system Software, modelling, understanding systematics... But... Not modular enough. Turnaround too long; thermally inefficient Constant race to make whole system work as proof-of-principle rather than focusing on small-scale key issues of transport and storage Too ambitious for tiny group of people!

UK nEDM: The way forward Two-pronged approach: Short to medium term: Join PSI effort - maintain world lead with incremental results maximise return on former UK investment Longer-term vision: Join new collaboration – small-scale R&D focus on specific problems at core of cryoEDM retain leadership in ultimate sensitivity expt

PSI Using our old apparatus, but with improved systematics This is the only nEDM experiment currently taking data 3E-25 ecm/day: approx same as us in ’02 same E, a; longer T but lower N Problem with source D2 crystal (snow vs ice?) is limiting statistics; gradually improving Expected results: ~ Factor 2 in 3 years ~ Factor 6 in ~6 or 7 years, from upgrade

New ILL-based collaboration Collaboration just formed: ILL: To develop new source, with magnetic confinement, on high-intensity custom beamline Munich: High-quality magnetic shielded environment (with room-temperature experiment as staging post for ultimate cryogenic expt) RAL/Sussex: Focus on cryogenic EDM insert to be put in magnetic shield. Removes enormous drain of running source/shields Focus exclusively on key areas, with much less effort Realistically [my view!] 8-10 years before cryogenic experiment running. Good match to PSI timescales.

Worldwide nEDM Searches Back in ’02 it was just us. Now a very active field... SNS J-PARC ILL PSI FRMII TRIUMF RCNP PNPI

SNS Cryogenic experiment: LHe ~100 collaborators UCN production within measurement volume – no separate source Scintillation from 3He capture to measure precession frequency ~100 collaborators Technically very challenging. Commissioning date slipped from 2012 (in ‘05) to at least 2020. Recent DOE review: New project mgmt, focus on specific technical issues. Many tricky areas... Aim: ~4E-28 ecm/yr. (Originally 5E-29 ecm.)

PNPI Phase I at ILL. Aim ~1E-26 ecm; initial goal was to reach this level by 2008. Currently halted, restarting 2015. Phase II: Large and well resourced facility being built at Gatchina, with solid D2 source. Aim ~1E-27 ecm. Timescale uncertain.

RCNP/TRIUMF UCN production in HeII, extraction to room-temp Source intensity probably limited by heating ~30 collaborators Phase I aim ~5E-27 ecm, but still quite some way from realisation Eventually move to TRIUMF for ~5E-28 ecm?

Others New effort just started at Los Alamos: room-temp experiment with Hg magnetometer. Will take several years. JPARC: (33 collaborators) Solid D2 source under development; first calculations suggest 1E-27 ecm may be possible. In very early stages. Crystal diffraction: JPARC, NIST. Early R&D work. Federov, PNPI, ongoing for some years; eventual stated goal 1E-27 ecm.

Electron EDM Record was held by Hinds (IC) group, using YbF beam, until Oct 2013 overtaken by ACME collaboration (Harvard, Yale, UCLA...) using ThO. Limit currently stands at |de| < 8.7 x 10−29 e.cm However, UK is not out of the race...

M R Tarbutt, B E Sauer, J J Hudson and E A Hinds Proposed YbF fountain Design for a fountain of YbF molecules to measure the electron's electric dipole moment M R Tarbutt, B E Sauer, J J Hudson and E A Hinds New J. Phys. 15 (2013) 053034 4K Fantastically inefficient: 10-8 from cell to detector. But T = 300ms, so 60 h of data gives sd = 3x10-31 e.cm!

EDM conclusion EDM physics of increasing interest worldwide UK should capitalise on investment and maintain world lead Science Board recognised that CryoEDM was too ambitious for small group to deliver; recommended joining or forming another int’l collaboration Two-pronged approach: PSI to maximise return on previous investment, and deliver incremental results in short-medium term Small-scale R&D focusing on technical challenges of cryogenic experiment for longer-term sensitivity eEDM: New approach offers prospect of regaining world lead.

spare slides

UCN production in liquid helium ln = 8.9 Å; E = 1.03 meV Landau-Feynman dispersion curve for 4He excitations Dispersion curve for free neutrons R. Golub and J.M. Pendlebury Phys. Lett. 53A (1975), Phys. Lett. 62A (1977) 1.03 meV (11 K) neutrons downscatter by emission of phonon in liquid helium at 0.5 K Upscattering suppressed: Boltzmann factor e-E/kT means not many 11 K phonons present We have demonstrated production rate consistent with anticipated.

UCN detection in liquid helium Solid-state detectors developed for use in LHe Thin surface film of 6LiF: n + 6Li  a + 3H

New beamline ILL funded (800 k€) Installation 2014 Should have 4x intensity Need to characterise: - intensity - spectrum - polarisation