On the basis of revisions of some of the systematic errors, we reanalyzed the electron-antineutrino angular correlation (𝑎 coefficient) in free neutron decay inferred from the recoil energy spectrum of the protons which are detected in 4𝜋 by the aSPECT spectrometer. With 𝑎=−0.104 02(82), the new value differs only marginally from the one published in 2020. Here, the experiment also has 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% confidence interval region of −0.041 ≤ 𝑏 ≤ 0.022 on this hypothetical term. Tighter constraints on 𝑏 can be set from a combined analysis of the PERKEO III (𝛽 asymmetry) and aSPECT measurement which suggests a finite value of 𝑏 with 𝑏(𝑐)=−0.0181 ± 0.0065 deviating by 2.82𝜎 from the standard model.
Beck, Marcus, et al. "Reanalysis of the 𝛽− $\overline{v}$<sub>𝑒</sub> Angular Correlation Measurement from the aSPECT Experiment with New Constraints on Fierz Interference." Physical Review Letters, vol. 132, no. 10, Mar. 2024. https://doi.org/10.1103/PhysRevLett.132.102501
Beck, Marcus, Heil, Werner, Schmidt, Christian, Baeßler, Stefan, Glück, Ferenc, Konrad, Gertrud, & Schmidt, Ulrich (2024). Reanalysis of the 𝛽− $\overline{v}$<sub>𝑒</sub> Angular Correlation Measurement from the aSPECT Experiment with New Constraints on Fierz Interference. Physical Review Letters, 132(10). https://doi.org/10.1103/PhysRevLett.132.102501
Beck, Marcus, Heil, Werner, Schmidt, Christian, et al., "Reanalysis of the 𝛽− $\overline{v}$<sub>𝑒</sub> Angular Correlation Measurement from the aSPECT Experiment with New Constraints on Fierz Interference," Physical Review Letters 132, no. 10 (2024), https://doi.org/10.1103/PhysRevLett.132.102501
@article{osti_2583794,
author = {Beck, Marcus and Heil, Werner and Schmidt, Christian and Baeßler, Stefan and Glück, Ferenc and Konrad, Gertrud and Schmidt, Ulrich},
title = {Reanalysis of the 𝛽− $\overline{v}$<sub>𝑒</sub> Angular Correlation Measurement from the aSPECT Experiment with New Constraints on Fierz Interference},
annote = {On the basis of revisions of some of the systematic errors, we reanalyzed the electron-antineutrino angular correlation (𝑎 coefficient) in free neutron decay inferred from the recoil energy spectrum of the protons which are detected in 4𝜋 by the aSPECT spectrometer. With 𝑎=−0.104 02(82), the new value differs only marginally from the one published in 2020. Here, the experiment also has 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% confidence interval region of −0.041 ≤ 𝑏 ≤ 0.022 on this hypothetical term. Tighter constraints on 𝑏 can be set from a combined analysis of the PERKEO III (𝛽 asymmetry) and aSPECT measurement which suggests a finite value of 𝑏 with 𝑏(𝑐)=−0.0181 ± 0.0065 deviating by 2.82𝜎 from the standard model.},
doi = {10.1103/PhysRevLett.132.102501},
url = {https://www.osti.gov/biblio/2583794},
journal = {Physical Review Letters},
issn = {ISSN 0031-9007},
number = {10},
volume = {132},
place = {United States},
publisher = {American Physical Society (APS)},
year = {2024},
month = {03}}
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