Figure 1

Experimental $\beta$ spectra for the two detectors compared to the theoretical spectrum from about 1400 keV up to the endpoint. At lower energies the difference between the theoretical and experimental spectra continues to increase. As can be seen, above 1700 keV (i.e., the lower edge of the region used for analysis) distortions of the spectrum are minimal, thereby also limiting the effect in the final result related to the accuracy of the GEANT4-based simulation code that has to take care of the distortions. Inset: The low-energy part of the $\beta$ spectrum showing the $\gamma$ rays from ${}^{57}\mathrm{Co}$ and the K (162 keV) and L $+$ M (186 and 189 keV) conversion electron lines from ${}^{114}\mathrm{In}$ that were used for the energy calibration. The energy resolution for the 162 keV K-conversion electron line is 4.5 keV.Reuse & Permissions

Figure 2

$\beta$ anisotropy of ${}^{114}\mathrm{In}$ for the region between 1.700 and 1.830 MeV, in a field of 0.046 T (${\chi }^2/\nu =0.71$).Reuse & Permissions

Figure 3

Limits (90% C.L.) on time-reversal-invariant tensor couplings from correlation measurements in nuclear $\beta$ decay: the Fierz interference term $b_{\mathrm{Fierz}}$ from a spectrum shape measurement for ${}^{114}\mathrm{In}$ (with only statistical errors quoted) [43, 44], the $\beta$-asymmetry parameter $\mathit{Ã}$ in the decay of ${}^{114}\mathrm{In}$ (this work) and in free neutron decay [5], and the $\beta$-$\nu$ correlation coefficient $a$ in the decays of ${}^6\mathrm{He}$ [45, 46] and ${}^{21}\mathrm{Na}$ [47] (see also Ref. [17]). Limits for the mixed Fermi-GT transitions of the neutron and ${}^{21}\mathrm{Na}$ are for scalar couplings $C_S=C_S^{\text{'}}=0$.Reuse & Permissions