A Lithium Experiment in the Program of Solar Neutrino Research

The experiments sensitive to pp-neutrinos from the Sun are very perspective for the precise measurement of a mixing angle ${\theta }_{12}$. A $\nu$e${}^{-}$ scattering experiment (Xmass) and/or a charged-current experiment (the indium detector) can measure the flux of electron pp-neutrinos. One can find the total flux of pp-neutrinos from a luminosity constraint after the contribution of ${}^7$Be and CNO neutrinos to the total luminosity of the Sun are measured. The radiochemical experiment utilizing a lithium target has the high sensitivity to the CNO neutrinos, thus, it has a good promise for the precise measurement of a mixing angle and for the test of a current theory of the evolution of the stars.