Statistical combination of searches for the $\rm{X^{\pm}(5568)}$ state decaying into $\rm{B^0_s \pi^\pm}$

Abstract

A statistical combination of the search results for the narrow $\rm{X^{\pm}(5568)}$ resonance decaying into $\rm{B_s^0 \pi^+}$ is reported, based on published results from the ATLAS, CMS, CDF and LHCb Collaborations. A structure in the invariant mass distribution of $\rm{B_s^0 \pi^+}$ has been observed by the D0 Collaboration with a mass value of 5568 MeV but not confirmed by any of the latest searches from the other Collaborations. Limits have been set on the relative production rate $\rm{\rho_X}$ of the $\rm{X^{\pm}(5568)}$ and $\rm{B^0_s}$ states, times the branching ratio for the decay $\rm{X^{\pm}(5568) \rightarrow B^0_s\pi^\pm}$. By applying a statistical combination of limits set by the three LHC experiments, we derive a limit at 95\% Confidence Level of $\rho_X < 0.0092$ for $p_T(B^0_s)>$ 10 GeV, and $\rho_X < 0.0091$ for $p_T(B^0_s)>$ 15 GeV, superseding the previous most stringent upper limits. The effect of including the CDF result in the combination is also discussed.