Search for the Flavor-Changing Neutral Current Decay $B_s^0\to {\mu }^{+}{\mu }^{-}$ in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{T}\mathrm{e}\mathrm{V}$ with the D0 Detector

We present the results of a search for the flavor-changing neutral current decay $B_s^0\to {\mu }^{+}{\mu }^{-}$ using a data set with integrated luminosity of $240{\mathrm{p}\mathrm{b}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{T}\mathrm{e}\mathrm{V}$ collected with the D0 detector in run II of the Fermilab Tevatron collider. We find the upper limit on the branching fraction to be $\mathcal{B}(B_s^0\to {\mu }^{+}{\mu }^{-})\le 5.0\times {10}^{-7}$ at the 95% C.L. assuming no contributions from the decay $B_d^0\to {\mu }^{+}{\mu }^{-}$ in the signal region. This limit is the most stringent upper bound on the branching fraction $B_s^0\to {\mu }^{+}{\mu }^{-}$ to date.

Figure 1

Discriminating variables after the preselection for signal MC (solid line) and data events (dashed line) from the sidebands. The arrows indicate the discriminating values that were obtained after optimization. The normalization is done on the number of signal MC and sideband data events after preselection.

Figure 2

Invariant mass of the remaining events of the full data sample after optimized requirements on the discriminating variables.

Figure 3

Invariant mass distribution for candidates in the normalization channel $B^{\pm }\to J/\psi K^{\pm }$.