Importance of fluctuations of cross sections in muon-catalysed t-t fusion reactions

We discuss the reaction rate of the muon-catalysed $t$-$t$ fusion. The reaction rate is determined as a function of the temperature using the model of "in flight" fusion. We especially take into account the effect of the fluctuation of the cross section due to the existence of the muon. The obtained reaction rate 5.0$\times10^{-3} \mu$s$^{-1}$ is a factor of 10$^{-3}$ smaller than the experimental muonic cycling rate in the solid tritium target.