Measurement of the neutrino asymmetry in the β decay of laser-cooled, polarized 37K

D. Melconian, J. A. Behr, D. Ashery, O. Aviv, P. G. Bricault, M. Dombsky, S. Fostner, A. Gorelov, S. Gu, V. Hanemaayer, K. P. Jackson, M. R. Pearson, I. Vollrath

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A measurement of the neutrino asymmetry is presented which represents the first search for new physics using polarized radioactive atoms initially cooled and confined in a magneto-optical trap. Optical pumping and photoionization techniques are used to generate and measure, in situ, a highly spin-polarized (96.5 (0.8) %) sample of the short-lived β+-emitter 37K. The angular distribution of neutrinos from this polarized decay, inferred from the daughter recoil asymmetry, is used to search for a hypothetical V + A current in the weak interaction. We find the ν asymmetry parameter to be Bν = - 0.755 ± 0.020 (stat) ± 0.013 (syst), in agreement with the standard model's purely V - A interaction.

Original languageEnglish
Pages (from-to)370-375
Number of pages6
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number5-6
StatePublished - 14 Jun 2007


  • Atom trapping
  • Neutrino asymmetry
  • Nuclear β decay
  • Optical pumping
  • Parity violation
  • Right-handed currents


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