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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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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