First measurements of the branching fractions for the decay modes Ξ0𝑐 →Λ⁢𝜂 and Ξ0𝑐 →Λ⁢𝜂′ and search for the decay Ξ0𝑐 →Λ⁢𝜋0 using Belle and Belle II data

Physical Review A: Atomic, Molecular, and Optical physics. 2026. Vol. D 113. Article 032015.

Bodrov D., Pakhlova G., Aushev Т., Abumusabh М.

Using data samples of 988.4 fb^-1 and 427.9 fb^-1 collected with the Belle and Belle II detectors, we present a study of the singly Cabibbo-suppressed decays Xi0_c -> Lambda eta, Lambda eta', and Lambda pi0. We observe the decay Xi0_c -> Lambda eta and find evidence for the decay Xi0_c -> Lambda eta', with corresponding branching ratios determined to be B(Xi0_c -> Lambda eta) / B(Xi0_c -> Xi- pi+) = (4.16 +/- 0.91 +/- 0.23)% and B(Xi0_c -> Lambda eta') / B(Xi0_c -> Xi- pi+) = (2.48 +/- 0.82 +/- 0.12)%, respectively. We find no significant signal in the Xi0_c -> Lambda pi0 decay mode and set an upper limit at the 90% credibility level of B(Xi0_c -> Lambda pi0) / B(Xi0_c -> Xi- pi+) < 3.5%. Multiplying these ratios by the world-average branching fraction of the normalization channel, B(Xi0_c -> Xi- pi+) = (1.43 +/- 0.27)%, we obtain the absolute branching fractions of B(Xi0_c -> Lambda eta) = (5.95 +/- 1.30 +/- 0.32 +/- 1.13) x 10^-4, B(Xi0_c -> Lambda eta') = (3.55 +/- 1.17 +/- 0.17 +/- 0.68) x 10^-4, and an upper limit at the 90% credibility level on the absolute branching fraction of B(Xi0_c -> Lambda pi0) < 5.2 x 10^-4. The quoted first and second uncertainties are statistical and systematic, respectively, while the third uncertainties arise from the branching fraction of the normalization mode. These results are consistent with most theoretical predictions and further the understanding of the underlying decay mechanisms.

Keywords: the Belle and Belle II detectors

Publication based on the results of: Search for New physics in the experiments on e+e- colliders (2025)