Precision measurement of the nuclear polarization in laser-cooled, optically pumped ${}^{37}\mathrm{K}$

Abstract

We report a measurement of the nuclear polarization of laser-cooled, optically-pumped ${}^{37}\mathrm{K}$ atoms which will allow us to precisely measure angular correlation parameters in the beta-decay of the same atoms. These results will be used to test the $V-A$ framework of the weak interaction at high precision. At the TRIUMF Neutral Atom Trap (TRINAT), a magneto-optical trap (MOT) confines and cools neutral ${}^{37}\mathrm{K}$ atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of $P=0.9913\pm 0.0008$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the beta-asymmetry has $0.2\%$ statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to $<0.1\%$, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.

arXiv comment32 pages, 11 figures, submitted to New Journal of Physics

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Cited by in corpus (7)

• New physics searches in nuclear and neutron $\beta$ decay
• Precision measurement of the $\beta$-asymmetry in spin-polarized ${}^{37}\mathrm{K}$ decay
• All orders factorization and the Coulomb problem
• The MORA project
• Field Theory of the Fermi Function
• Analog-antianalog isospin mixing in ${}^{47}$K ${\beta }^{-}$ decay
• $A_{\beta }[E_{\beta }]$ in ${}^{37}$K decay: new physics with opposite $\beta$ helicity