Search for the rare decays K(L)→π0π0µ+µ- and K(L)→π0π0X0→π0π0µ+µ-.

ABSTRACT

The KTeV E799 experiment has conducted a search for the rare decays, K(L)→π(0)π(0)µ(+)µ(-) and K(L)→π(0)π(0)X(0)→π(0)π(0)µ(+)µ(-), where the X(0) is a possible new neutral boson that was reported by the HyperCP experiment with a mass of (214.3 ± 0.5) MeV/c(2). We find no evidence for either decay. We obtain upper limits of Br(K(L)→π(0)π(0)X(0)→π(0)π(0)µ(+)µ(-)) < 1.0 × 10(-10) and Br(K(L)→π(0)π(0)µ(+)µ(-)) < 9.2 × 10(-11) at the 90% confidence level. This result rules out the pseudoscalar X(0) as an explanation of the HyperCP result under the scenario that the dsX(0) coupling is completely real.