Measurements of the Branching Fractions of the Semileptonic Decays Ξc0 → Ξ-l+νl and the Asymmetry Parameter of Ξc0 → Ξ-π+

Using data samples of 89.5 and 711 fb-1 recorded at energies of s=10.52 and 10.58 GeV, respectively, with the Belle detector at the KEKB e+e- collider, we report measurements of branching fractions of semileptonic decays Ξc0→Ξ-ℓ+νℓ (ℓ=e or μ) and the CP-asymmetry parameter of Ξc0→Ξ-π+ decay. The branching fractions are measured to be B(Ξc0→Ξ-e+νe)=(1.31±0.04±0.07±0.38)% and B(Ξc0→Ξ-μ+νμ)=(1.27±0.06±0.10±0.37)%, and the decay parameter αΞπ is measured to be 0.63±0.03±0.01 with much improved precision compared with the current world average. The corresponding ratio B(Ξc0→Ξ-e+νe)/B(Ξc0→Ξ-μ+νμ) is 1.03±0.05±0.07, which is consistent with the expectation of lepton flavor universality. The first measured asymmetry parameter ACP=(αΞ-π++αΞ¯+π-)/(αΞ-π+-αΞ¯+π-)=0.024±0.052±0.014 is found to be consistent with zero. The first and the second uncertainties above are statistical and systematic, respectively, while the third ones arise due to the uncertainty of the Ξc0→Ξ-π+ branching fraction.