| Resumen |
We report evidence for a narrow structure, X(5568), in the decay sequence X(5568)→B 0 s π±, B 0 s →J/ψϕ,
J/ψ→μ + μ −, ϕ→K + K −. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m=5567.8±2.9(stat) +0.9 −1.9 (syst) MeV/c 2 and Γ=21.9±6.4(stat) +5.0 −2.5 (syst) MeV/c 2. If the decay is X(5568)→B ∗ s π± →B 0 s γπ± with an unseen γ, m(X(5568)) will be shifted up by m(B ∗ s )−m(B 0 s )∼49 MeV/c 2. This measurement is based on 10.4 fb−1 of pp̄ collision data at √s =1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. |
