Observation of Orbitally Excited $B_s$ Mesons

We report the observation of two narrow resonances consistent with states of orbitally excited ($L=1$) $B_s$ mesons using $1{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected with the Collider Detector at Fermilab II detector at the Fermilab Tevatron. We use two-body decays into $K^{-}$ and $B^{+}$ mesons reconstructed as $B^{+}\to J/\psi K^{+}$, $J/\psi \to {\mu }^{+}{\mu }^{-}$ or $B^{+}\to {\overline{D}}^0{\pi }^{+}$, ${\overline{D}}^0\to K^{+}{\pi }^{-}$. We deduce the masses of the two states to be $m(B_{s1})=5829.4\pm 0.7\mathrm{MeV}/c^2$ and $m(B_{s2}^{*})=5839.6\pm 0.7\mathrm{MeV}/c^2$.

Figure 1

Distribution of $Q=m(B^{+}{K}^{-})-m(B^{+})-M_{K^{-}}$ for the $B_s^{**}$ candidates with (a) $B^{+}\to J/\psi K^{+}$, (b) $B^{+}\to {\overline{D}}^0{\pi }^{+}$ and (c) both $B^{+}$ channels combined. The dotted line shows the result of a fit with the sum of a background function and two Gaussians. The filled area shows the $Q$ distribution for the wrong-sign combination $B^{+}{K}^{+}$.