Oscillation search study using $\tau$-to-electron decay channel in the CHORUS experiment

The CHORUS experiment is designed to search for $\nu_{\mu}\rightarrow \nu_{\tau}$ oscillation by detection of $\nu_{\tau}$ in a $\nu_{\mu}$ neutrino beam, with three decay channels of the tau lepton. These are the $\;\;\tau^{-}\rightarrow \mu^{-}\nu_{\tau}\overline{\nu}_{\mu}$, $\;\;\tau^{-}\rightarrow h^{-}(n\pi^{0})\nu_{\tau}\;\;$ and $\;\;\tau^{-}\rightarrow \pi^{+}\pi^{-}\pi^{+}(n\pi^{0})\nu_{\tau}$ decay channels. In this thesis the possibility of using the $\;\;\tau^{-}\rightarrow e^{-}\nu_{\tau}\overline{\nu}_{e}\;\;$ decay channel of the tau lepton, for $\nu_{\tau}$ detection with the CHORUS detector, is studied. A $95\%$ electron identification efficiency is obtained. When all detection efficiencies are taken into account, $4-6 \%$ improvement on $\sin^{2}2\theta_{\mu\tau}$ limit at large $\Delta m^{2}$ is achieved without any extra emulsion scanning load.