A precision measurement of ϵ′\epsilon^{\prime}/ϵ\epsilon in CP violating K0^{0} →\rightarrow 2π\pi decays

The prime goal of the experiment is to measure the CP violating parameter Re($\epsilon^{\prime}/\epsilon$) with an accuracy of $2 \times 10 ^{-4}$. The experiment uses two nearly collinear $K _{S}$ and $K _{L}$ beams produced concurrently and distinguished by tagging the protons producing the $K _{S}$ component. In this way the double ratio $R$ of decay rates of the $K_{L}$ and $K_{S}$ into two pions, \\\\ $R=1-6\cdot Re(\frac{\epsilon^\prime}{\epsilon}) =\frac{\mid\eta_{00}\mid^{2}}{\mid\eta_{+-}\mid^{2}} =\frac{\Gamma(K_{L} \rightarrow \pi^{0} \pi^{0})} {\Gamma(K_{S}\rightarrow \pi^{0} \pi^{0})}/ \frac{\Gamma(K_{L}\rightarrow \pi^{+} \pi^{-})} {\Gamma(K_{S}\rightarrow \pi^{+}\pi{-})}$ \\\\is measured with minimal systematic uncertainties. Charged mode decays $K \rightarrow \pi^{+} \pi^{-}$ are measured in a magnetic spectrometer with a central dipole magnet and two pairs of large and high precision drift chambers on each side. Neutral mode decays $K \rightarrow \pi^{0}\pi^{0}$ are recorded in a ten m$^{3}$ homogeneous liquid krypton calorimeter. This novel detector has fine transverse segmentation (2x2) cm$^{2}$, energy resolution better than 1% above 10~GeV shower energy and sub-nanosecond time resolution. Data from all sub-detectors are collected fully pipelined, merged locally and sent from the experiment site to the computer centre over a fast optical network. The data taking periods for Re($\epsilon^{\prime} /\epsilon$) in 1997 and 1998 have yielded more than $2.5 \times 10^{6} K_{L}\rightarrow 2 \pi^{0}$ decays. NA48 will run in the two next years at least, in 1999 and 2000.\\\\ Formula to come here