CP-violation in the decay neutral kaon ---> positive pion negative pion neutral pion.

Abstract

Although CP-violation has been known to occur for 23 years, the only places it has been seen is in the neutral kaon decays to $\pi\sp+\pi\sp-$ and $\pi\sp0\pi\sp0$. This thesis is about results from the test run of Fermilab E621, the first high statistics search for CP violation in neutral kaon decays to $\pi\sp+\pi\sp-\pi\sp0$. We used a dual beam setup with an upstream target to measure the acceptance. The decays were detected with a magnetic spectrometer made of 6 multi-wire proportional chambers and an array of 86 lead glass blocks. There were two trigger devices to reduce the number of triggers from $\Lambda$ $\to$ p $\pi\sp-$. One used hodoscopes to require symmetry in the charged tracks and the other required two neutral clusters in the glass. The final sample was over 83,000 kaons decaying in this mode. Although no CP violation was observed, we set new limits on its existence. We looked for an interference term in the proper time distribution of decays, which was characterized by an complex number known as $\eta\sb{+-0}$. The final result was Re$\sp\prime$ ($\eta\sb{+-0}$) = 0.074 $\pm$ 0.055 and Im$\sp\prime$ ($\eta\sb{+-0}$) = $-$0.238 $\pm$ 0.222 with D (a scale factor) from K$\sp+$/K$\sp-$ cross-sections. Using D = 1, the answer is Re$\sp\prime$ ($\eta\sb{+-0}$) = 0.061 $\pm$ 0.029 and Im$\sp\prime$ ($\eta\sb{+-0}$) = $-$0.089 $\pm$ 0.086. Most of the error on the imaginary part comes from being highly correlated with the normalization.