Electron-antineutrino spectrum from precision measurements of ${}^{144}$Pr-decay

The ${}^{144}$Ce – ${}^{144}$Pr electron antineutrino source is one of the most suitable radiochemical sources for experiments searching for the oscillations of active neutrinos to the light sterile state. In the current work the $\beta$-spectra of ${}^{144}\mathrm{C}\mathrm{e}$ – ${}^{144}\mathrm{P}\mathrm{r}$ source have been measured by two types of $\beta$-spectrometers based on silicon Si(Li) detectors in order to determine the energy spectrum of electron anti-neutrino emitted in the $\beta$-decay of ${}^{144}\mathrm{P}\mathrm{r}$ nuclei. The nuclear shape factor of the ground state beta transition in ${}^{144}\mathrm{P}\mathrm{r}-{}^{144}\mathrm{N}\mathrm{d}$ has been obtained with high precision: $C(W)=1+(-0.0301\pm 0.0007)W+(-0.101\pm 0.006)W^{-1}$. The reduced cross section for the inverse beta decay reaction on hydrogen for the ${}^{144}\mathrm{P}\mathrm{r}$ electron anti-neutrino source has been defined as $(4.7344\pm {0.0006}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}}\pm {0.013}_{\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}})\times {10}^{-44}\mathrm{c}{\mathrm{m}}^2{\mathrm{d}\mathrm{e}\mathrm{c}\mathrm{a}\mathrm{y}}^{-1}$ that provides sufficient sensitivity to search for a sterile neutrino with a mass of $m_4\sim 1$~eV and a mixing angle $Si{n}^2(2{\theta }_{14})\sim 0.005$ using standard disappearance method.