A MEASUREMENT OF Ξ~0 BETA DECAY BY NA48/1 AND THE EXTRACTION OF V_(US)

摘要

A large sample of Ξ~0 decays was collected by the NA48/1 collaboration at the CERN SPS accelerator during a high-intensity K_S and hyperon run in 2002. Clean signals for the semileptonic decays Ξ~0 → Σ~+e~-v_e and Ξ~0 → Σ~+ μ~- v_μ have been obtained. The measurement of the Ξ~0 → Σ~+ e~- v_e branching ratio has been used to extract V_(us). This measurement is of special interest because recent results on V_(us), obtained mostly from "Ke3" decays of neutral and charged kaons (K → πev), in combination with measured values for V_(ud) seemed to be in conflict with the unitarity condition of the CKM matrix.