Electric Dipole Moment Experiments Philip Harris University of Sussex PPAP meeting July 2016
Electric Dipole Moments • EDMs are P, T odd • Complementary study of CPv: must test elsewhere than K, B • Constrains models of new physics • Strong & SUSY CP problems • ALPs – dark matter • Baryon asymmetry • SM CPv inadequate • New models bring larger EDMs • Clean system – background free • n, Hg, e • complementary systems more or less equally sensitive to new physics + E g p × n n p g squark q q gaugino
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. • 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
EDM Landscape C. R. Physique 13 168 (2012)
nEDM experiment Larmor precession: () – () = – 4 E d/ h if no change in B. Use Hg magnetometer to compensate B drift: Basis of our ‘99 world best limit, PRL 82, 904
nEDM experiment • New systematic! False EDM induced by field gradient dB/dz + relativity • ... but n/Hg frequency ratio also sensitive to field gradient Phys. Rev. A 70, 032102 (2004) ... + corrections for small dipole/quadrupole fields etc Basis of our ‘06 world best limit, PRL 82, 904 ...but slope of lines was free parameter...
Gravitational depolarisation • New systematic: nonlinear frequency shifts from vertical striation under gravity Harris et al, PRD 89,016011 • Validated against earlier PSI data Afach et al., PRD 92,052008 • Complete reanalysis revised world limit Pendlebury et al., PRD 92, 092003 ... and slope now matches expectation. UK holds 17-year world lead
PSI • Using our old apparatus upgraded, with improved systematics • This is the only nEDM experiment currently taking data • ~1.2x10-25 ecm/day, c.f. 2.1x10-25 ecm/day at ILL • Blinded (Sx algo) from 2015 • Will reach s~1x10-26 ecmin 2016
n2EDM: The way forward • Double UCN chamber • Better phase-space match to source: 7x UCN density • World’s brightest UCN source • Much better magnetometry/syst. • Shielded room 2.5M CHF ordered • Order of magnitude improvement • Realistic timeline: 2020 start • Proven technology • We should be part of it!
Other results Can set new limits on axion-like particles... DM candidates Preliminary • Also: • Lorentz invariance • Spin-dept forces • Mirror matter • ... and just ask about • our neat new • spin-echo technique!
Worldwide nEDM Searches Back in ’02 it was just us. Now a very active field... PNPI FRMII TRIUMF ILL J-PARC PSI LOS ALAMOS SNS RCNP
Beyond n2EDM:Is the future fully cryogenic? • PSI is superthermal (cryogenic) source; world’s brightest • Could put experiment in LHe too, potentially increasing E • ... but CryoEDM R&D showed how difficult it is: • transport • storage • detection • turnaround times • B-field monitoring • cost • This is long term - in contrast n2EDM has readily achievable order of magnitude, taking us deep into SUSY parameter space • Can do modest cryo R&D on the side • Let’s keep the UK’s world lead in this field! USA cryo nEDM experiment:
UK R&D* • Sussex: • Systematics, Monte Carlo • HV • Magnetometry: new 3He technology • n2EDM design/coordination roles • Some cryogenic/HV studies • RAL: • UCN guide development: • sputtering at PPD, electroplating at TD • Tests using beamtime awarded at ILL • Technology available for wider UCN community Long-term plans: LoI for UCN source @ ESS *In addition to ongoing PSI nEDM involvement
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...
YbF Electron EDMMeasurement Create YbF Pump Split Evolve Recombine Probe
YbF Electron EDMIncreasing the number of molecules in the experiment Put more molecules into the initial state Detect the molecules better at the final stage • Before: • 2x population in initial state • Now: • 9x population in initial state • Before: • 700 molecules detected per shot • Now: • Expect to detect 17,000 molecules per shot (24x) increase) Total signal increase (expected): factor 216
YbF Electron EDM Signal:noise increases as (√signal) • Timeline • EDM test run to start late 2016 • 2017: Investigation and control of systematics at 10-29 e.cm level • 2018: Full dataset, aiming for |de| sensitivity 2x10-29 e.cm (90%), c.f. current upper limit |de| < 8.7x10-29 e.cm (90%)
EDM conclusion • EDM physics of increasing interest worldwide • UK should capitalise on investment and maintain world lead • Strong leadership in PSI experiment (e.g. CB chair, n2EDM syst. coord, blinding algo, magnetometry...) • New experiment n2EDM will deliver order of magnitude: we should be part of it! • eEDM: New approach offers prospect of regaining world lead.
Notes... for PPAP’s future reference Major changes in the status of a project on the international stage • PSI experiment now running, very smoothly and fully blinded, as of autumn 2015. • It has overtaken previous Sussex/RAL/ILL experiment’s sensitivity • Excellent proof-of-principle for complete replacement experiment n2EDM (not just “upgrade”) • Plan: stop running end 2016, some systematics studies early 2017, then make way for n2EDM Changes in the funding approval status internationally • For n2EDM, the 2.5 M CHF magnetically shielded room has been ordered; delivery late 2017 • French groups have ongoing grant funding for n2EDM involvement confirmed Transitions in project status such as moving from construction to operation • Earlier than anticipated end to current PSI (end 2016), for transition to n2EDM The emergence or demise of projects in competition with the one you are describing • RCPI/TRIUMF: not clear when, or if, source will move from Japan to Canada. Delays. • USA SNS: Technical review has forced collaboration to focus on key roadblock issues. Still strongly supported, and progress is being made, but far behind original schedule. • Los Alamos: New project developed as “plan B” because of delays in SNS • ILL/FRM/RAL: Source development underway, but apparently so substantive plan to progress towards nEDM experiment • PNPI (& ILL): Intermediate result (5x10-26 ecm), but including 1990 data. Substantial new facility being built in Gatchina. Timescales not clear. General tech developments relevant to area • New spin-echo technique to give precise measurements of spectrum and also of B-field gradient, for all UCN physics • 3He magnetometry, with Cs magnetometer readout, will give precise measurements of field shape and stability • RAL UCN guide developments potentially useful across the field – in particular, unusual guide geometries • Ongoing studies of cryogenic HV behaviour useful for long term
More notes... for PPAP’s future reference .... UK neutron EDM (nEDM) effort is focused in the short term on operation and analysis of data of a room-temperature experiment at PSI, based on largely UK-designed and built apparatus that set the current world limit. The UK group is renowned for its detailed analysis of systematics. In the medium term a replacement (n2EDM) based on known technology is planned, expected to start running in ~2020 with a sensitivity goal of about an order of magnitude after 4 years. With a view to the longer term, development of a cryogenic nEDM apparatus building on the substantial UK expertise in that area may be possible, and this might ultimately deliver a further factor ~3. This could perhaps take place at PSI post-n2EDM, or at ILL or ESS; RAL has joined ILL/Munich collaboration to this end. Scientific Goals: • Complementary studies of CP (i.e. time-reversal) symmetry violation to those in the quark and neutrino sectors, sensitive to BSM models including non-minimal SUSY and with relevance to baryogenesis. UK Leadership and Responsibilities: • Historically, UK-led and -based experiments have been at the cutting edge. The eEDM experiment remains under development at Imperial College. • Chair of Collaboration Board on PSI experiment; leading in various aspects of analysis including systematics, blinding • Have been asked to address magnetometry, HV and core design issues for next-generation n2EDM experiment • RAL developing neutron guides UK Institutes: • eEDM: Imperial College; nEDM: RAL, Sussex eEDM Milestones: • EDM test run to start late 2016 • 2017: Investigation and control of systematics at 10-29 e.cm level • 2018: Full dataset, aiming for |de| sensitivity 2x10-29 e.cm (90%) nEDM Milestones: • 2016: Measurement with sensitivity at the level of ~1×10-26 ecm at PSI • 2020: Commissioning of next-generation n2EDM apparatus at PSI, for ~2×10-27 ecm sensitivity in 4 years • 2026: Possible commissioning of prototype cryogenic experiment
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!
UCN spin-echo: New diagnostic tool Flip spins part way through 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 PRL (2015) 115, 162502 (“Editor’s Choice”) We can now measure the neutron spectrum directly!
SNS • Cryogenic experiment: LHe • UCN production within measurementvolume – no separate source • Scintillation from 3He capture to measure precession frequency • ~100 collaborators • Technically very challenging. Commissioning date slipped from 2012 (in ‘05) to circa 20222. • 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 development in Japan; anticipated move to TRIUMF, timescale unknown • Source intensity probably limited by heating? • ~30 collaborators • Phase I aim ~5E-27 ecm, but still quite some way from realisation
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. Project is in very early stages. • Crystal diffraction: JPARC, NIST. Early R&D work. Federov, PNPI, ongoing for some years; eventual stated goal 1E-27 ecm. • Beam nEDM: very challenging proposal for ESS.