Study of the ${X^\pm(5568)}$ state with semileptonic decays of the ${B_s^0}$ meson

Abstract

We present a study of the $X^\pm(5568)$ using semileptonic decays of the $B_s^0$ 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, $X^\pm(5568)$, in the decay sequence $X^\pm(5568) \to B_s^0 \pi^\pm$ where $B_s^0 \rightarrow \mu^\mp D_s^\pm \, \mathrm{X}$, $D_s^\pm \rightarrow \phi \pi^{\pm}$ which is consistent with the previous measurement by the D0 collaboration in the hadronic decay mode, $X^\pm(5568) \to B^0_s \pi^\pm$ where $B^0_s \to J/\psi\phi$. The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding $m = 5566.9 ^{+3.2}_{-3.1} \thinspace {\rm (stat)} ^{+0.6}_{-1.2} {\rm \thinspace (syst)}$\,MeV/$c^2$, $\Gamma = 18.6 ^{+7.9}_{-6.1} {\rm \thinspace (stat)} ^{+3.5}_{-3.8} {\rm \thinspace (syst)} $\,MeV/$c^2$ with a significance of 6.7$\,\sigma$.