Computation of the number of neutrino events which can be registered in Borexino detector from the Sun neutrinos flux with energy $E_\nu = 0.862 MeV$
This paper gives an estimation of the number of neutrinos which can be registered in Borexino detector from the Sun neutrinos generated in reaction $^{7}Be + e^{-} \to ^{7}Li + \nu_e$ with energy $E_{\nu_e} = 0.862 MeV$ in the absence of neutrino oscillations. This number is supposed be between $ N^{theor} = 86.45 \div 96.52 \frac{counters}{(day\cdot 100\quad ton)}$ in dependence on primary neutrino fluxes. Then ratios between number of neutrinos $N^{exper}$ registered in Borexino detector and counted numbers $N^{theor}$, are $\frac{N^{exper}}{N^{theor}} = 0.49 \div 0.54$. This value is close enough to the same value obtained in $^{71}Ga - ^{71}Ge$ experiments in the close energy regions. The value $\frac{N^{exper}}{N^{theor}}$ obtained at supposition that $\theta_{1 3} \approx 0$ and absence of the resonance effect approximately equal to $\simeq 0.67$ and it is noticeably greater than the above value. Probably it means that the supposition that $\theta_{1 3} \approx 0$ is not justified and there can be a definite deposit of $\tau$ neutrinos.