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UCN beta decay

UCN beta decay. Dan Melconian University of Washington. n. e. W. n. p. Neutron beta decay. (SM). Experiments in beta decay show:. and. to 1%. and. and. Angular correlations. The canonical expression (JTW 1957):. and in the SM,. with. But there’s also …. Not as famous, but is a

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UCN beta decay

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  1. UCN beta decay Dan Melconian University ofWashington

  2. n e W n p Neutron beta decay (SM)

  3. Experiments in beta decay show: and to 1% and and

  4. Angular correlations The canonical expression (JTW 1957): and in the SM, with

  5. But there’s also … Not as famous, but is a P- and T-odd observable

  6. Present values PDG 06: To be competitive: Measure all of these parameters to 0.1% Sensitive to new physics (leptoquarks, SUSY, RHC, extra Higgs, …) Search for non V-A interactions (S,T currents, RH currents); CVC and Vud

  7. Neutrons, Vud and current discrepancies

  8. Limits on RH currents

  9. Beta asymmetry parameter if you can measure A, you’re pretty much ready to measure B • UCNA – LANL • PERKEO – ILL • abBA – SNS • - PNPI (cold)

  10. UCNA at Los Alamos Goal: measure beta asymmetry to 0.2% using UCNs (easy to transport and polarize) • started ~ 1998 • hoping for 2% measurement this year • production run in 2008?

  11. And here’s reality …

  12. UCNA decay region and 1st UCN beta spectrum

  13. Beta-neutrino correlation F. Wietfeldt • acorn - NIST Also: • aSPECT - Munich • Nab/abBA - SNS

  14. D-coefficient • emiT P. Mumm

  15. P. Mumm

  16. PSI R-correlation measurement

  17. Recent neutron lifetimes • In-beam • bottle • meas exp • decay UCN are (relatively) easy to trap! PDG doesn’t know what to do with Serebrov result …

  18. E.g.: UCN Gravitrap also: Ioffe trap (NIST); magnetic trap in 4He (NCState);

  19. And yet others … (TRIUMF?) J. Nico

  20. My (personal!) thoughts … • All these experiments are tough • All these experiments have lifetimes on the scale of decades • Any new experiment needs to happen quickly and should have a new angle • A 2x104 UCN/cm3 source would be worth it! • TRIUMF is more attractive than LANL • After this round of experiments, what’s next for fundamental neutron physics …??

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