American Physical Society

Abstract

Limits at the 10 -4 level are reported for rare and forbidden decays of the D 0 charm meson to a pair of leptons and either a vector meson or two pseudoscalar mesons.Of these searches, 18 are investigations of decays without previous published results; several others have significantly improved sensitivity over previous results.We have made blind searches for 27 dilepton D 0 decays with muons or electrons. 1he modes are resonant D 0 → V ℓ + ℓ -decays, where V is a ρ 0 , K * 0 , or φ, and non-resonant D 0 → hhℓℓ decays, where h is a π or K. Charge-conjugates are implied.The modes are lepton flavor-violating, or lepton number-violating, or flavorchanging neutral current decays.Box diagrams can mimic FCNC decays, but only at the 10 -10 to 10 -9 level. 2,3Long range effects (e.g.D 0 → K * 0 ρ 0 , ρ 0 → e + e -) can occur at the 10 -6 level. 3,4Many have studied rare decays of -1/3q strange quarks.Charge 2/3 charm quarks are interesting because they might couple differently. 5Data is from the Fermilab E791 spectrometer. 6The spectrometer has been upgraded for a series of experiments including E516, 7 E691, 8 E769, 9 and E791.In addition to searching for rare decays, 1,10 E791 has set limits on D 0 D 0 mixing 11

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