Measurement of CP Violation parameters in neutral kaon decay of two charged pions

The CPLEAR experiment at CERN uses the neutral kaon system to make measurements of CP violating parameters. Neutral kaons are produced from the annihilation of stopped anti-protons in a gaseous hydrogen target. Neutral kaons are produced in the reaction $p\overline{p}$(at rest)$\to K^-\pi^+K^0$ and $p\overline{p}$(at rest)$\to K^+\pi^-\overline{K}^0$, where the strangeness of the neutral kaon is tagged by the sign of the charge of the charged kaon. CP violating parameters are extracted by constructing asymmetries between the $K^0$ and $\overline{K}^0$ decay rates. This thesis presents a measurement of $\eta_{+-}$, the parameter describing CP violation in the $\pi^+\pi^-$ decay mode. From a selected data sample of 63 Million events, collected during the period 1992-5 inclusive.