Another Route to CP Violation Beyond the SM – Particle Dipole Moments Dave Wark Imperial/RAL WIN05 Delphi June 10, 2005

…and CP nEDM… WIN05 June 10 ’05 Particle Electric Dipole Moment + _ s ⇀ Would lead to a non-zero value for d n, either parallel or anti-parallel to s ⇀ ⇀ d n would be: P odd T odd CP odd! ⇀ Imperial College/RAL Dave Wark

Standard Model Range of d (e cm) in various models electron neutron …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

 Left-Right Multi Higgs SUSY  Standard Model Electro- magnetic Range of d (e cm) in various models neutron electron Strong CPV  d n ~ e  cm …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

Range of d (e cm) in various models neutron electron Relative value of neutron and electron EDM is model- dependent, must pursue both Strong CPV  d n ~ e  cm …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

Range of d (e cm) in various models neutron electron Cited >200 times already Strong CPV  d n ~ e  cm …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

I f neutron were the size of the earth... xx -e +e... current EDM limit would correspond to charge separation of  x  10 . …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

BB d n ?? BE Basic Idea of the Measurement …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

BB d n ?? BE Basic Idea of the Measurement Look for a shift in the Larmor frequency of 2·E·d n as E is flipped relative to B …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

Free precession... Apply  /2 spin flip pulse... “Spin up” neutron... Second  /2 spin flip pulse. The Ramsey Separated Oscillator Method …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

…and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

>> interatomic spacing; neutrons see Fermi potential V F Critical velocity for reflection: ½mv c 2 = V F Ultracold neutrons (UCN): v  6 m/s: total internal reflection possible. v c depends on orientation of neutron spin, so can polarise by transmission. n n n s s B …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

Prepare neutrons in polarisation state 1, execute Ramsey cycle and measure the number left in states 1 and 2, repeat with B and E fields parallel (  ) and anti-parallel (  ), then: With the resulting “statistical” sensitivity: Must add any systematics to this to determine the sensitivity of the experiment. …and CP nEDM… WIN05 June 10 ’05 Imperial College/RAL Dave Wark

The Institute Laue-Langevin …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

N S 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 Hg u.v. lamp RF coil to flip spins Magnet UCN polarising foil UCN guide changeover Ultracold neutrons (UCN) UCN detector Current Room- Temperature nEDM Experiment …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

…and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

1999 Results (PG Harris et al, PRL 82, 904 (1999)) d n = (1.9  5.4)  10  26 e cm  d n  6.3  10  26 e cm (90% c.l.) …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

Published Data Current Room-Temp Cryogenic Experiment Recall: α E T N kV/cm 130 s kV/cm 130 s …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

How will we do better? Need a new source of UCN…. To use this we need… meV …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

Next Generation Experiment …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

Ramsey Cell and SF Vessel …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

Published Data Current Room-Temp Cryogenic Experiment Recall: α E T N kV/cm 130 s kV/cm 130 s kV/cm 300 s …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

…and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

199 Hg Electric Dipole Moment hep-ex/ Optically pumped 199 Hg atoms precess in B, E fields, modulating absorption signal Dual cells remove effect of drifts in B Result: d( 199 Hg) < 2.1 x e cm Provides good limit on CPv effects in nuclear forces, inc.  QCD If from valence neutron, corresponds to d n <2x ecm, because of electrostatic shielding. …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL

Slide from Ed Hinds

Conclusions Particle EDMs are sensitive probes of CP violation both within (  s < 2-6 x ) and in models beyond the SM (The natural scale for the nEDM is SUSY is , already stressed). Experiments are in progress to improve sensitivities by factors There are other competing experiments for both neutrons (PSI, US) and electrons that I have no time to discuss. There are also plans to push limits on the muon EDM at future facilities (JPARC). The two CP violation communities seem completely separate, which is a pity…. …and CP nEDM… WIN05 June 10 ’05 Dave Wark Imperial College/RAL