Reanalysis of the $\beta-\bar\nu_e$ angular correlation measurement aSPECT with new constrains on Fierz interference

Author:

M. Beck, W. Heil, C. Schmidt, S. Baeßler, F. Glück, G. Konrad, U. Schmidt

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex)

journal:

date:

2023-08-29 16:00:00

Abstract

On the basis of revisions of some of the systematic errors, we reanalyzed the measurement of the $\beta-\bar\nu_e$ angular correlation ($a$ coefficient) in free neutron beta decay from the aSPECT experiment. With $a = -0.10402(82)$ the new value differs only marginally from the one published in 2020. The experiment has also sensitivity to $b$, the Fierz interference term. From a correlated $(b,a)$ fit to the proton recoil spectrum, we derive a limit of $b= -0.0098(193)$ which translates into a somewhat improved 90% CL region of $-0.041 < b < 0.022$ on this hypothetical term.

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