Search for the semileptonic decays Ξc0 → Ξ0ℓ ℓ- at Belle

Abstract

Using the full data sample of 980 fb-1 collected with the Belle detector at the KEKB asymmetric energy electron-positron collider, we report the results of the first search for the rare semileptonic decays Ξc0→Ξ0ℓ+ℓ- (ℓ=e or μ). No significant signals are observed in the Ξ0ℓ+ℓ- invariant-mass distributions. Taking the decay Ξc0→Ξ-π+ as the normalization mode, we report 90% credibility upper limits on the branching fraction ratios B(Ξc0→Ξ0e+e-)/B(Ξc0→Ξ-π+)<6.7×10-3 and B(Ξc0→Ξ0μ+μ-)/B(Ξc0→Ξ-π+)<4.3×10-3 based on the phase-space assumption for signal decays. The 90% credibility upper limits on the absolute branching fractions of B(Ξc0→Ξ0e+e-) and B(Ξc0→Ξ0μ+μ-) are found to be 9.9×10-5 and 6.5×..