  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.
