Study of the X±(5568 ) state with semileptonic decays of the Bs0 meson

We present a study of the X^±(5568 ) using semileptonic decays of the B_s⁰ meson using the full run II integrated luminosity of 10.4 fb^-1 in proton-antiproton collisions at a center of mass energy of 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. We report evidence for a narrow structure, X^±(5568 ), in the decay sequence X^±(5568 )→B_s⁰π^± where B_s⁰→μ^∓D_s^±X , D_s^±→ϕ π^± which is consistent with the previous measurement by the D0 Collaboration in the hadronic decay mode, X^±(5568 )→B_s⁰π^± where B_s⁰→J /ψ ϕ . The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding m =5566.9_-3.1^+3.2(stat₎^{-1.2 +0.6}(syst ) MeV /c² , Γ =18.6_-6.1^+7.9(stat₎^{-3.8 +3.5}(syst ) MeV /c² with a significance of 6.7 σ .