arXiv subjects
Publications and source records attributed to KTeV Collaboration.
We have compared the decay rates of K_L and K_S to π^+ π^- and π^0 π^0 final states using a subset of the data from the KTeV experiment (E832) at Fermilab. We find that the direct-CP-violation parameter Re(ε'/ε) is equal to (28.0 \pm 3.0 (stat) \pm 2.8 (syst)) \times 10^{-4}. This result definitively establishes the existence of CP violation in a decay process.
We report on two null searches, one for the spontaneous appearance of $π^+π^-$ pairs, another for a single $π^0$, consistent with the decay of a long-lived neutral particle into hadrons and an unseen neutral particle. For the lowest level gluon-gluino bound state, known as the $R^0$, we exclude the decays $R^0\to π^+π^-\tildeγ$ and $R^0\to π^0\tildeγ$ for the masses of $R^0$ and $\tildeγ$ in the theoretically allowed range. In the most interesting $R^0$ mass range, $\leq 3 GeV/c^2$, we exclude $R^0$ lifetimes from $3\times 10^{-10}$ seconds to as high as $10^{-3}$ seconds, assuming perturbative QCD production for the $R^0$.