Search for the Rare Decays K_L→π~0π~0μ+μ- and K_L→π~0π~0μ+μ-→π~0π~0μ+μ-

摘要

The KTeV E799 experiment has conducted a search for the rare decays, K_L→π~0π~0μ+μ- and K_L→π~0π~0μ+μ-→π~0π~0μ+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/c2. We find no evidence for either decay. We obtain upper limits of Br(K_L→π~0π~0X~0→π~0π~0μ+μ-) < 1.0 × 10~(-10) and Br(K_L→π~0π~0μ+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.