2019 Joint Workshop on Future charm-tau Factory

We presented new technique of the measurement cross section at $e^{+}e^{-}$ collider. This approach base on study angular distribution in laboratory frame as function of energy near threshold, when center mass system has non-zero velocity. Such technique can be used at Super Charm-Tau Factory. Super Charm-Tau Factory has Crab Waist collision scheme of the interaction point. It gives the velocity of the center mass system $\sim 0.03c$. We complied feasibility study of this technique for the $e^{+}e^{-}\to n\bar{n}$ process. In case standard way, main contribution in invariant mass resolution is beam energy spread. Our study allows one obtain invariant mass resolution from beam energy spread much smaller then gives widely used approach. On the threshold, relative resolution depend on $\delta E_{b}/E_{b}\sim10^{-3}$ for widely used approach. For new one technique relative invariant mass resolution depend as $(\delta E_{b}/E_{b})^{2}\sim10^{-6}$. We assume that contributions from other factors are large. New technique allows one reach invariant mass resolution $\delta W/W\sim10^{-4}$. This gives possibility study fine structure of the cross section near threshold.