Search for the Semileptonic Decays Ξc0→Ξ0ℓ+ℓ− at Belle

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 6.5×10−5, respectively.Received 7 December 2023Accepted 21 February 2024DOI:https://doi.org/10.1103/PhysRevD.109.052003Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Physical SystemsBaryonsCharm quarkTechniquesParticle decaysParticles & Fields