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Neutron Electric Dipole Moment

Neutron Electric Dipole Moment. By: Christopher Hayes Physics 564 12/01/2007. Properties of the Neutron. M n =939.565MeV T n =885.7 s  =  n •  N • S n d n < 2.9x10 -26 e·cm. s n. u. d n. d. d. u. u. d. d. d. d. d. d. u. Symmetry Operations.

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Neutron Electric Dipole Moment

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  1. Neutron Electric Dipole Moment By: Christopher Hayes Physics 564 12/01/2007

  2. Properties of the Neutron Mn=939.565MeV Tn=885.7 s  = n• N • Sn dn< 2.9x10-26 e·cm sn u dn d d

  3. u u d d d d d d u Symmetry Operations T[dn]= dn T[sn]= -sn P[dn]= -dn P[sn]= sn

  4. Consequences of a Non-Zero nEDM • First direct observation of T-violation • Second observation of CP violation • Evidence that the Strong Force does not conserve parity • A new clue to the origin of the baryon asymmetry of the universe

  5. nEDM and Extensions of the SM

  6. nEDM Measurement Principle z B, E h1= 2n• B + 2dn • E h2= 2n• B - 2dn • E h  = h (2-1) =4dn • E y n dn dn = h /4E x

  7. Experiment to Measure nEDM B = 10-3 Gauss E = 10kV/cm Larmor~ 30 Hz N ~ 15,000 Vbottle ~ 20 liters Cycle ~ 200 s

  8. Measured Precession FrequenciesSuperimposed on Alternating E-field

  9. Ultra Cold Neutrons (UCN’s) • UCN Energies…………..En ~ 0.2eV • UCN Speeds…………….Vn ~ 6 m/s • UCN Wavelengths………n ~ 60nm • Only UCN neutrons are capable of total internal reflection • Transport pipes and EDM storage cell operate on the principle of Total Internal Reflection

  10. Production of UCN’s Nuclear Reactor or Spallation in High Z targets E ~ 2 MeV Moderator (Heavy water) E ~ 2 meV UCN Turbine E ~ .2 eV

  11. Results of EDM experiments • First EDM test result in 1950: dn ~ 10-18 e•cm • Current upper limit measured at ILL: dn< 2.9 x 10-26 e•cm • Next generation experiments: dn< 10-28 e•cm

  12. How to Improve Results • Increase Electric field Strength dn ~ E • Increase neutron density d ~ [a·E·T ·(N)1/2]-1 • Increase storage times • Increase polarization efficiency

  13. Research Facilities • Institut Laue-Langevin (ILL): Grenoble, France • Petersburg Nuclear Physics Institute (PNPI): Gatchina, Russia • Paul Scherrer Institute (PSI): Villigen Switzerland • Los Alamos National Laboratory (LANL)/Los Alamos Neutron Science Center (LANCE)

  14. EDM for other particles • Can measure EDMs for protons, electrons, muons, and other particles de= .07 x 10-26 e•cm d = 3.7 x 10-19 e•cm dp< .54 x 10-23 e•cm

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