Beta spectrum of unique first-forbidden decays as a novel test for fundamental symmetries

Ayala Glick-Magid, Yonatan Mishnayot, Ish Mukul, Michael Hass, Sergey Vaintraub, Guy Ron, Doron Gazit*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Within the Standard Model, the weak interaction of quarks and leptons is characterized by certain symmetry properties, such as maximal breaking of parity and favored helicity. These are related to the V−A structure of the weak interaction. These characteristics were discovered by studying correlations in the directions of the outgoing leptons in nuclear beta decays. Presently, correlation measurements in nuclear beta decays are intensively studied to probe for signatures for deviations from these couplings, which are an indication of Beyond Standard Model physics. We show that the structure of the energy spectrum of emitted electrons in unique first-forbidden β-decays is sensitive to the symmetries of the weak interaction, and thus can be used as a novel probe of physics beyond the standard model. Furthermore, the energy spectrum gives constraints both in the case of right and left couplings of the new beyond standard model currents. We show that a measurement with modest energy resolution of ≈20 keV is expected to lead to new constraints on beyond the standard model interactions with tensor couplings.

Original languageAmerican English
Pages (from-to)285-288
Number of pages4
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - 10 Apr 2017

Bibliographical note

Publisher Copyright:
© 2017 The Author(s)


  • Beta decay spectrum
  • Beyond the Standard Model
  • Forbidden transitions
  • Weak interaction


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