Observation of Direct CP Violation in K_{S,L} to ππDecays

Abstract

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.

12 pages, 4 figures; minor text revisions; submitted to Phys. Rev. Lett

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