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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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Mund D, Märkisch B, Deissenroth M, Krempel J, Schumann M, Abele H, Petoukhov A, Soldner T. Determination of the weak axial vector coupling λ = gA/gV from a measurement of the β-asymmetry parameter A in neutron beta decay. Phys Rev Lett 2013; 110:172502. [PMID: 23679712 DOI: 10.1103/physrevlett.110.172502] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 01/11/2013] [Indexed: 06/02/2023]
Abstract
We report on a new measurement of the neutron β-asymmetry parameter A with the instrument Perkeo II. The main enhancements are the high neutron polarization of P = 99.7(1)% from a novel arrangement of supermirror polarizers and reduced background from improvements in beam line and shielding. The leading corrections were thus reduced by a factor of 4, pushing them below the level of statistical error and resulting in a significant reduction of systematic uncertainty compared to our previous experiments. We derive the β-asymmetry parameter A0 = -0.11972(45)(stat)((-44)(+32))(sys) = -0.11972((-65)(+53)) and the ratio of the axial vector to the vector coupling constant λ = gA/gV = -1.2761(12)(stat)((-12)(+9))(sys) = -1.2761((-17)(+14)).
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Affiliation(s)
- D Mund
- Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany
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Schumann M, Kreuz M, Deissenroth M, Glück F, Krempel J, Märkisch B, Mund D, Petoukhov A, Soldner T, Abele H. Measurement of the proton asymmetry parameter in neutron beta decay. Phys Rev Lett 2008; 100:151801. [PMID: 18518094 DOI: 10.1103/physrevlett.100.151801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Indexed: 05/26/2023]
Abstract
The proton asymmetry parameter C in neutron decay describes the angular correlation between neutron spin and proton momentum. In this Letter, the first measurement of this quantity is presented. The result C= -0.2377(26) agrees with the standard model expectation. The coefficient C provides an additional parameter for new and improved standard model tests.
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Affiliation(s)
- M Schumann
- Physikalisches Institut der Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany.
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Schumann M, Soldner T, Deissenroth M, Glück F, Krempel J, Kreuz M, Märkisch B, Mund D, Petoukhov A, Abele H. Measurement of the neutrino asymmetry parameter B in neutron decay. Phys Rev Lett 2007; 99:191803. [PMID: 18233064 DOI: 10.1103/physrevlett.99.191803] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Indexed: 05/25/2023]
Abstract
A new measurement of the neutrino asymmetry parameter B in neutron decay, the angular correlation between neutron spin and antineutrino momentum, is presented. The result, B=0.9802(50), confirms earlier measurements but features considerably smaller corrections. It agrees with the standard model expectation and permits updated tests on "new physics" in neutron decay.
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Affiliation(s)
- M Schumann
- Physikalisches Institut der Universität Heidelberg, Philosophenweg 12, 69120, Heidelberg, Germany.
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Abele H, Baeßler S, Deissenroth M, Glück F, Krempel J, Kreuz M, Märkisch B, Mund D, Schumann M, Soldner T. The Beta-, Neutrino- and Proton-Asymmetry in Neutron β-Decay. J Res Natl Inst Stand Technol 2005; 110:377-381. [PMID: 27308153 PMCID: PMC4852813 DOI: 10.6028/jres.110.056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 08/11/2004] [Indexed: 06/06/2023]
Abstract
This article describes measurements of angular-correlation coefficients in the decay of free neutrons with the superconducting spectrometer PERKEO II. A method for measuring the β-asymmetry coefficient A is presented, as well as a new method for determining the neutrino-asymmetry coefficient B, which allows a value for the proton-asymmetry coefficient C to be obtained for the first time. An ongoing experiment is trying to improve the accuracy of these quantities.
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Affiliation(s)
- H Abele
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - S Baeßler
- Physikalisches Institut der Universität Mainz, Staudingerweg 7, D-55128 Mainz, Germany
| | - M Deissenroth
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - F Glück
- Physikalisches Institut der Universität Mainz, Staudingerweg 7, D-55128 Mainz, Germany
| | - J Krempel
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - M Kreuz
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - B Märkisch
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - D Mund
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - M Schumann
- Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany
| | - T Soldner
- Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9, France
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