THE ELECTRON ASYMMETRY IN THE BETA DECAY OF POLARIZED NEUTRONS

1961 ◽  
Vol 39 (1) ◽  
pp. 13-21 ◽  
Author(s):  
M. A. Clark ◽  
J. M. Robson
Keyword(s):  
Angular Correlation ◽  
Beta Decay ◽  
Axial Vector ◽  
Coupling Constants ◽  
Neutron Spin ◽  
Neutron Decay ◽  
Vector Coupling ◽  
Polarized Neutrons ◽  
Spin Direction

The coefficient of the angular correlation between the electron direction and the neutron spin direction in the beta decay of the neutron has been measured using a beam of polarized neutrons. The coefficient of this correlation is −0.09 ± 0.05. This implies that CA/CV, the ratio of the axial vector to vector coupling constants in neutron decay, is equal to −1.20 ± 0.12.

scholarly journals The Nab experiment: A precision measurement of unpolarized neutron beta decay

2019 ◽  
Vol 219 ◽  
pp. 04002 ◽  
Author(s):  
J. Fry ◽  
R. Alarcon ◽  
S. Baeßler ◽  
S. Balascuta ◽  
L. Barrón Palos ◽  
...  
Keyword(s):  
Beta Decay ◽  
Nuclear Physics ◽  
Axial Vector ◽  
Electron Neutrino ◽  
Coupling Constants ◽  
Neutron Lifetime ◽  
Large Area ◽  
Vector Coupling ◽  
Oak Ridge ◽  
Neutron Beta Decay

Neutron beta decay is one of the most fundamental processes in nuclear physics and provides sensitive means to uncover the details of the weak interaction. Neutron beta decay can evaluate the ratio of axial-vector to vector coupling constants in the standard model, λ = gA/gV, through multiple decay correlations. The Nab experiment will carry out measurements of the electron-neutrino correlation parameter a with a precision of δa/a = 10−3 and the Fierz interference term b to δb = 3 × 10−3 in unpolarized free neutron beta decay. These results, along with a more precise measurement of the neutron lifetime, aim to deliver an independent determination of the ratio λ with a precision of δλ/λ = 0.03% that will allow an evaluation of Vud and sensitively test CKM unitarity, independent of nuclear models. Nab utilizes a novel, long asymmetric spectrometer that guides the decay electron and proton to two large area silicon detectors in order to precisely determine the electron energy and an estimation of the proton momentum from the proton time of flight. The Nab spectrometer is being commissioned at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source at Oak Ridge National Lab. We present an overview of the Nab experiment and recent updates on the spectrometer, analysis, and systematic effects.

scholarly journals Angular Distributions of Emitted Electrons in the Two-Neutrino ββ Decay

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 147
Author(s):  
Ovidiu Niţescu ◽  
Rastislav Dvornický ◽  
Sabin Stoica ◽  
Fedor Šimkovic
Keyword(s):  
Nuclear Structure ◽  
Angular Correlation ◽  
Beta Decay ◽  
Axial Vector ◽  
Correlation Factor ◽  
Decay Rates ◽  
Double Beta Decay ◽  
Angular Distributions ◽  
Matrix Elements ◽  
Vector Coupling

The two-neutrino double-beta decay (2νββ-decay) process is attracting more and more attention of the physics community due to its potential to explain nuclear structure aspects of involved atomic nuclei and to constrain new (beyond the Standard model) physics scenarios. Topics of interest are energy and angular distributions of the emitted electrons, which might allow the deduction of valuable information about fundamental properties and interactions of neutrinos once a new generation of the double-beta decay experiments will be realized. These tasks require an improved theoretical description of the 2νββ-decay differential decay rates, which is presented. The dependence of the denominators in nuclear matrix elements on lepton energies is taken into account via the Taylor expansion. Both the Fermi and Gamow-Teller matrix elements are considered. For nuclei of experimental interest, relevant phase-space factors are calculated by using exact Dirac wave functions with finite nuclear size and electron screening. The uncertainty of the angular correlation factor on nuclear structure parameters is discussed. It is emphasized that the effective axial-vector coupling constant gAeff can be determined more reliably by accurately measuring the angular correlation factor.

Measurement of the vector and axial vector coupling constants in Λ

1981 ◽  
Author(s):  
D. A. Jensen ◽  
M. N. Kreisler ◽  
F. Lomanno ◽  
R. Poster ◽  
M. S. Z. Rabin ◽  
...  
Keyword(s):  
Axial Vector ◽  
Coupling Constants ◽  
Vector Coupling ◽  
Axial Vector Coupling

scholarly journals Two neutrino double-beta decay and effective axial-vector coupling constant

2018 ◽  
Vol 194 ◽  
pp. 02002
Author(s):  
Fedor Šimkovic ◽  
Rastislav Dvornický ◽  
Dušan Štefánik
Keyword(s):  
Beta Decay ◽  
Axial Vector ◽  
Double Beta Decay ◽  
Matrix Elements ◽  
Coupling Constant ◽  
Vector Coupling ◽  
Majorana Particle ◽  
Vector Coupling Constant ◽  
Novel Approach ◽  
Axial Vector Coupling

The theoretical and experimental study of the two-neutrino double-beta decay (2νββ-decay) is of crucial importance for reliable calculation of matrix elements governing the neutrinoless double-beta decay (0νββ-decay). That will allow to determine masses of neutrinos once the 0νββ-decay, which occurs if the neutrino is a massive Majorana particle and the total lepton number is not onserved, will be observed. Experiments studying the 2νββ-decay are currently approaching a qualitatively new level, where high-precision measurements are performed not only for half-lives but for all other observables of the process. In this context an improved formula for the 2νββ-decay is presented. Further, a novel approach for determining the effective axial-vector coupling constant is proposed.

The vector and axial-vector coupling constants of the nucleon in cavity QCD to order αs

1993 ◽  
Vol 560 (4) ◽  
pp. 1003-1013 ◽  
Author(s):  
P.R. Page ◽  
R.J. Lindebaum ◽  
R.D. Viollier
Keyword(s):  
Axial Vector ◽  
Coupling Constants ◽  
Vector Coupling ◽  
Axial Vector Coupling

scholarly journals Axial-vector coupling constants and chiral-symmetry restoration

1992 ◽  
Vol 46 (1) ◽  
pp. 431-437 ◽  
Author(s):  
E. M. Henley ◽  
W-Y. P. Hwang ◽  
L. S. Kisslinger
Keyword(s):  
Chiral Symmetry ◽  
Axial Vector ◽  
Coupling Constants ◽  
Chiral Symmetry Restoration ◽  
Vector Coupling ◽  
Axial Vector Coupling
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