$\beta$-nuclear-recoil correlation from $^6$He decay in a laser trap

TL;DR

This paper presents a precise measurement of the beta-recoil correlation from trapped $^6$He atoms, providing new limits on exotic tensor contributions to weak interactions, with implications for physics beyond the Standard Model.

Contribution

First precise measurement of beta-recoil correlation from radioactive noble gas in a magneto-optical trap, setting new constraints on tensor currents in weak interactions.

Findings

Limits on tensor current contributions: |C_T/C_A|^2 ≤ 0.022 (right-handed neutrinos)

Constraints for left-handed neutrinos: 0.007 < C_T/C_A < 0.111

Measurement limited by experimental uncertainties in atom cloud and recoil detection

Abstract

We report the first precise measurement of a $\beta$-recoil correlation from a radioactive noble gas ($^6{\rm He}$) confined via a magneto-optical trap. The measurement is motivated by the search for exotic tensor-type contributions to the charged weak current. Interpreted as tensor currents with right-handed neutrinos, the measurements yield: $|C_T/C_A|^2\le 0.022$ (90\% C.L.). On the other hand, for left-handed neutrinos the limits are $0.007< C_T/C_A <0.111$~(90\%\ C.L.). The sensitivity of the present measurement is mainly limited by experimental uncertainties in determining the time response properties and the distance between the atom cloud and the micro-channel plate used for recoil ion detection.