Statistical combination of $X ^\pm$(5568) $\rightarrow B^0_s \pi^\pm$ searches

A statistical combination of the search results for the $\rm{X^{\pm}(5568) \rightarrow B^0_s \pi^\pm}$ decayis reported, based on published results from the ATLAS, CMS, CDF and LHCb Collaborations. A narrow structure in the invariant mass distribution of $\rm{B^0_s \pi^\pm}$ has been observed by the D0 Collaboration with a mass value of 5568 MeV and interpreted as the first observation of a possible tetra-quark state with four different flavours. The evidence of such a state was not confirmed by any of the latest searches from LHCb, CDF, ATLAS and CMS Collaborations. CDF and the LHC experiments have set limits on $\rm{\rho_X}$, the relative production rate of the X(5568) and $\rm{B^0_s}$ rates times the branching ratio for the $\rm{X^{\pm}(5568) \rightarrow B^0_s\pi^\pm}$ decay.With a statistical combination of limits set by the three LHC experiments, we derive a limit, at 95\% Confidence Level, of $\rm{\rho_X}$ < 0.92\% for $\rm{p_T(B^0_s)>}$ 10 GeV, and $\rm{\rho_X}$ < 0.91\%for $\rm{p_T(B^0_s)>}$ 15 GeV which represent the most stringent upper limits up to present.The contribution reviews the experimental results from Tevatron and LHC, describes the combination procedure and the obtained results. The effect of including the results from Tevatron in the combination is also discussed.