Measurement of the $S$-factor of the T($^1$H, $\gamma$)$^4$He reaction at astrophysical energies

The T($^1$H, $\gamma$)$^4$He reaction has been studied for the first time in the energy range $E_{\text{lab}}=12$–$34\,$keV in the laboratory coordinate system ($E=7.8$–$20.1\,$keV in the center-of-mass system). The study of this reaction is of interest because it is involved in the primary nucleosynthesis of $^4$He and is important for the theory of few-nucleon systems. The reported experiment improves the accuracy of the experimental determination of the $S$-factor of the T($^1$H, $\gamma$)$^4$He reaction by several times. The theoretical calculations of the $S$-factor of the T($^1$H, $\gamma$)$^4$He reaction still differ from the experimental values by a factor of about $2$.