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arXiv · 1005.5034

Precision measurements of the $^{60}$Co $\beta$-asymmetry parameter in search for tensor currents in weak interactions

F. Wauters·I. S. Kraev·D. Zákoucký·M. Beck·M. Breitenfeldt·V. De Leebeeck·V. V. Golovko·V. Yu. Kozlov·T. Phalet·S. Roccia·G. Soti·M. Tandecki·I. S. Towner·E. Traykov·S. Van Gorp·N. Severijns
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Abstract

The $\beta$-asymmetry parameter $\widetilde{A}$ for the Gamow-Teller decay of $^{60}$Co was measured by polarizing the radioactive nuclei with the brute force low-temperature nuclear-orientation method. The $^{60}$Co activity was cooled down to milliKelvin temperatures in a $^3$He-$^4$He dilution refrigerator in an external 13 T magnetic field. The $\beta$ particles were observed by a 500 ${\mu}m$ thick Si PIN diode operating at a temperature of about 10 K in a magnetic field of 0.6 T. Extensive GEANT4 Monte-Carlo simulations were performed to gain control over the systematic effects. Our result, $\widetilde{A} = -1.014(12)_{stat}(16)_{syst}$, is in agreement with the Standard-Model value of $-0.987(9)$, which includes recoil-order corrections that were addressed for the first time for this isotope. Further, it enables limits to be placed on possible tensor-type charged weak currents as well as other physics beyond the Standard Model.

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F. Wauters, I. S. Kraev, D. Zákoucký, M. Beck, M. Breitenfeldt, V. De Leebeeck, V. V. Golovko, V. Yu. Kozlov, T. Phalet, S. Roccia, G. Soti, M. Tandecki, I. S. Towner, E. Traykov, S. Van Gorp, N. Severijns. 2010-05-27. Precision measurements of the $^{60}$Co $\beta$-asymmetry parameter in search for tensor currents in weak interactions. https://doi.org/10.1103/physrevc.82.055502

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