* *(mainly neutron) Electric-Dipole Moment Searches Philip Harris Room-temperature nEDM expt: latest results CryoEDM: upcoming, 100x sensitivity Other EDM expts
dn = dns Electric Dipole Moments • EDMs are • P odd • T odd • Complementary approachto study of CPv; probenew physics • SM predictions v. small; othermodels typ. 106 larger... + E
Generating EDMs E.g. in SUSY: Assumptions: gg’a, sin(f)1, L200 GeV Gives u, d quark EDMs 3x10-24ecm 100 x current limit “SUSY CP” problem g coupling const g squark g’eif q q gaugino
Constraints on SUSY parameters MSUSY = 500 GeV tan b = 3 Pospelov & Ritz, hep-ph/0504231
SUSY, cont’d Lebedev et al., hep-ph/0402023
Measurement principle Use (Ramsey) NMR on ultracold neutrons in B,E fields () – () = – 4 E d/ h assuming B unchanged when E is reversed. B0 B0 B0 E E <Sz> = + h/2 h(0) h() h() <Sz> = - h/2 Level splitting we can resolve: <10-21 eV
Approx scale 1 m High voltage lead Magnetic field coil B E /analysing foil Apparatus Magnetic shielding Storage cell S N Magnet & polarizing foil Ultracold neutrons (UCN) UCN detector
Apparatus HV feedthru Neutron storage chamber B-field coils
Electric Field + - nEDM measurement • Keep track of neutron resonant frequency • Look for n freq changes correlated with changes in E
Mercury co-magnetometer Compensates B drift...
nEDM measurement Raw neutron frequency 29.9295 Corrected frequency 29.9290 29.9285 29.9280 -10 D B = 10 T Precession frequency (Hz) 29.9275 29.9270 29.9265 29.9260 0 5 10 15 20 25 Run duration (hours)
and, from Special Relativity, extra motion-induced field New systematic Two effects:
Bnet Br Bnet Bv Bv Bv Bnet Br Bnet Geometric Phase J. Pendlebury et al., PRA 70 032102 (2004) P. Harris, J. Pendlebury, PRA 73 014101 (2006) ... so particle sees additional rotating field Bottle (top view) Frequency shift E Looks like an EDM Unique signature: can eliminate it
Error budget (10-26e.cm)
Final Result New limit: |dn| < 3.0 x 10-26 e.cm (90% CL) (prev. limit 6.3 x 10-26 e.cm, PRL 82, 904 (1999)) Preprint hep-ex/0602020 provisional acceptance PRL www.neutronedm.org
Dispersion curve for free neutrons Landau-Feynman dispersion curve for 4He excitations ln = 8.9 Å; E = 1.03 meV 2. CryoEDM 100-fold improvement in sensitivity! R. Golub and J.M. Pendlebury Phys. Lett. 53A (1975), Phys. Lett. 62A (1977) More neutrons Higher E field Better polarisation Longer coherence time
CryoEDM overview Neutron beam input Cryogenic Ramsey chamber Transfer section
Cryogenic Ramsey chamber HV electrode HV feed Superfluid He n storage cells (eventually 4)
CryoEDM Turns on October 2006
3. Other EDM experiments: PSI • spallation target • D2O moderator • currently testing apparatus from ILL
Other nEDM experiments: USA • SNS at ORNL LANL-led testing underway not yet funded
Electron EDM: Berkeley State analyser laser Down beam E field B field State preparation laser Up beam • Use unpaired e-in paramagnetic atom • Pairs of Tl beams in opposite E fields • Na beams as comagnetometer Final result: de<1.6 x 10-27 e.cm (systematics limited)
Electron EDM measurements (This slide mainly from DeMille, PANIC ’05)
Molecule interferometer PMT Pulsed supersonic YbF beam source detection laser Yb target B E skimmer Ar+SF6 pulsed YAG laser Imperial College Electron EDM experiment J.J.Hudson, B.E. Sauer, M.R. Tarbutt, & E.A. Hinds, PRL. 89, 023003 (2002). state recombiner state splitter pump laser Now taking data Studying systematics Results soon
199Hg EDM • Optically pumped 199Hg atoms precess in B, E fields, modulating absorption signal • Dual cells remove effect of drifts in B • Result: d(199Hg) < 2.1 x 10-28 e cm • Provides good limit on CPv effects in nuclear forces, inc. qQCD
... and more! • Muon EDM: from g-2 (7E-19; proposal at JPARC for ~10-24) • Deuterium EDM: similarprinciple (may reach ~10-29 e.cm) • Tau weak dipole moment – look for CP-odd observables in diff. x-sec at Z res.(6E-18 e.cm from LEP data) Sensitivity to physics BSM depends on source of CPv
Conclusions • New nEDM limit, 3.0 x 10-26 e.cm • Tightens the constraints on beyond-SM CPv • Systematics understood as never before • CryoEDM coming soon – 100x more sensitive • Several new measurements starting up • Watch this space!
spare slides
Cryogenic Ramsey chamber HV electrode Superfluid He n storage cells
“Spin up” neutron... 1. Apply /2 spin flip pulse... 2. Free precession... 3. Second /2 spin flip pulse. 4. Ramsey method of Separated Oscillating Fields
Ramsey resonance • “2-slit” interference pattern • Phase gives freq offset from resonance
Four-layer mu-metal shield High voltage lead Quartz insulating cylinder Coil for 10 mG magnetic field Upper electrode Main storage cell Hg u.v. lamp PMT to detect Hg u.v. light Vacuum wall Mercury prepolarising cell RF coil to flip spins Hg u.v. lamp Magnet S N UCN guide changeover UCN polarising foil Ultracold neutrons (UCN) UCN detector nEDM apparatus
Stat. limit now 1.51 x 10-26 e.cm Neutron EDM results (binned)
What’s going on here, for example? Neutron EDM results (individual runs)
Geometric Phase How to measure it • Consider • Should have value 1 • R is shifted by magnetic field gradients • Plot EDM vs measured R-1:
Geometric Phase Magnetic field down
Geometric Phase Magnetic field up
The answer? B up B down Results EDM R-1 0 Nearly...
Results Small dipole/quadrupole fields can pull lines apart & add GP shifts EDM B up R-1 0 B down
Results Small dipole/quadrupole fields can pull lines apart & add GP shifts EDM B up R-1 0 Measure and apply correction ...difficult! B down
Now CryoEDM History Factor 10 every 8 years on average
Other nEDM experiments: Mainz • Testing UCN source at TRIGA, Mainz for later installation at FRM, Munich
The interference fringes Data being taken now. Systematics being studied. Current status: Expected 2010: de = _ ± 5 x 10-28 e.cm de = _ ± 5 x 10-29 e.cm Fluorescence signal EDM given by fringe shift with reversal of E or B Magnetic field (nT)
