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Saul H, Roick C, Abele H, Mest H, Klopf M, Petukhov AK, Soldner T, Wang X, Werder D, Märkisch B. Limit on the Fierz Interference Term b from a Measurement of the Beta Asymmetry in Neutron Decay. Phys Rev Lett 2020; 125:112501. [PMID: 32976008 DOI: 10.1103/physrevlett.125.112501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 07/22/2020] [Indexed: 06/11/2023]
Abstract
In the standard model of particle physics, the weak interaction is described by vector and axial-vector couplings only. Nonzero scalar or tensor interactions would imply an additional contribution to the differential decay rate of the neutron, the Fierz interference term. We derive a limit on this hypothetical term from a measurement using spin-polarized neutrons. This method is statistically less sensitive than the determination from the spectral shape but features much cleaner systematics. We obtain a limit of b=0.017(21) at 68.27% C.L., improving the previous best limit from neutron decay by a factor of four.
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Affiliation(s)
- H Saul
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - C Roick
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - H Abele
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - H Mest
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - M Klopf
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
| | - A K Petukhov
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - T Soldner
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - X Wang
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
| | - D Werder
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - B Märkisch
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
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Märkisch B, Mest H, Saul H, Wang X, Abele H, Dubbers D, Klopf M, Petoukhov A, Roick C, Soldner T, Werder D. Measurement of the Weak Axial-Vector Coupling Constant in the Decay of Free Neutrons Using a Pulsed Cold Neutron Beam. Phys Rev Lett 2019; 122:242501. [PMID: 31322367 DOI: 10.1103/physrevlett.122.242501] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Indexed: 06/10/2023]
Abstract
We present a precision measurement of the axial-vector coupling constant g_{A} in the decay of polarized free neutrons. For the first time, a pulsed cold neutron beam was used for this purpose. By this method, leading sources of systematic uncertainty are suppressed. From the electron spectra we obtain λ=g_{A}/g_{V}=-1.27641(45)_{stat}(33)_{sys}, which confirms recent measurements with improved precision. This corresponds to a value of the parity violating beta asymmetry parameter of A_{0}=-0.11985(17)_{stat}(12)_{sys}. We discuss implications on the Cabibbo-Kobayashi-Maskawa matrix element V_{ud} and derive a limit on left-handed tensor interaction.
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Affiliation(s)
- B Märkisch
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - H Mest
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - H Saul
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
- Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany
| | - X Wang
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
| | - H Abele
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
| | - D Dubbers
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - M Klopf
- Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
| | - A Petoukhov
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - C Roick
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
| | - T Soldner
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - D Werder
- Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
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Klopf M, Jericha E, Märkisch B, Saul H, Soldner T, Abele H. Constraints on the Dark Matter Interpretation n→χ+e^{+}e^{-} of the Neutron Decay Anomaly with the PERKEO II Experiment. Phys Rev Lett 2019; 122:222503. [PMID: 31283271 DOI: 10.1103/physrevlett.122.222503] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Indexed: 06/09/2023]
Abstract
Discrepancies from in-beam- and in-bottle-type experiments measuring the neutron lifetime are on the 4σ standard deviation level. In a recent publication Fornal and Grinstein proposed that the puzzle could be solved if the neutron would decay on the one percent level via a dark decay mode, one possible branch being n→χ+e^{+}e^{-}. With data from the Perkeo II experiment we set limits on the branching fraction and exclude a one percent contribution for 95% of the allowed mass range for the dark matter particle.
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Affiliation(s)
- M Klopf
- Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Wien, Austria
| | - E Jericha
- Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Wien, Austria
| | - B Märkisch
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - H Saul
- Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Wien, Austria
- Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - T Soldner
- Institut Laue-Langevin, BP 156, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - H Abele
- Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Wien, Austria
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