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Precision measurements at low energy search for physics beyond the Standard Model in a way complementary to searches for new particles at colliders. In the weak sector the most general $beta$ decay Hamiltonian contains, besides vector and axial-vector terms, also scalar, tensor and pseudoscalar terms. Current limits on the scalar and tensor coupling constants from neutron and nuclear $beta$ decay are on the level of several percent. The goal of this paper is extracting new information on tensor coupling constants by measuring the $beta$-asymmetry parameter in the pure Gamow-Teller decay of $^{67}$Cu, thereby testing the V-A structure of the weak interaction. An iron sample foil into which the radioactive nuclei were implanted was cooled down to milliKelvin temperatures in a $^3$He-$^4$He dilution refrigerator. An external magnetic field of 0.1 T, in combination with the internal hyperfine magnetic field, oriented the nuclei. The anisotropic $beta$ radiation was observed with planar high purity germanium detectors operating at a temperature of about 10,K. An on-line measurement of the $beta$ asymmetry of $^{68}$Cu was performed as well for normalization purposes. Systematic effects were investigated using Geant4 simulations. The experimental value, $tilde{A}$ = 0.587(14), is in agreement with the Standard Model value of 0.5991(2) and is interpreted in terms of physics beyond the Standard Model. The limits obtained on possible tensor type charged currents in the weak interaction hamiltonian are -0.045 $< (C_T+C_T)/C_A <$ 0.159 (90% C.L.). The obtained limits are comparable to limits from other correlation measurements in nuclear $beta$ decay and contribute to further constraining tensor coupling constants.
The $beta$-asymmetry parameter $widetilde{A}$ for the Gamow-Teller decay of $^{60}$Co was measured by polarizing the radioactive nuclei with the brute force low-temperature nuclear-orientation method. The $^{60}$Co activity was cooled down to milliKe
We present a detailed report of a measurement of the neutron $beta$-asymmetry parameter $A_0$, the parity-violating angular correlation between the neutron spin and the decay electron momentum, performed with polarized ultracold neutrons (UCN). UCN w
We report on a new measurement of the neutron beta-asymmetry parameter $A$ with the instrument perkeo. Main advancements are the high neutron polarization of $P = 99.7(1)%$ from a novel arrangement of super mirror polarizers and reduced background fr
We have measured the angular distribution of recoiling daughter nuclei emitted from the Gamow-Teller $beta$ decay of spin-polarized $^{80}$Rb. The asymmetry of this distribution vanishes to lowest order in the Standard Model (SM) in pure Gamow-Teller
The neutron $beta$-decay asymmetry parameter $A_0$ defines the correlation between the spin of the neutron and the momentum of the emitted electron, which determines $lambda=frac{g_{A}}{g_{V}}$, the ratio of the axial-vector to vector weak coupling c