Search for a Structure in the $B^0_s \pi^\pm$ Invariant Mass Spectrum with the ATLAS Experiment

A search for the narrow structure, $X(5568)$, reported by the D0 Collaboration in the decay sequence $X \to B^0_s \pi^\pm$, $B^0_s \to J/\psi\phi$, is presented. The analysis is based on a data sample recorded with the ATLAS detector at the LHC corresponding to 4.9 fb$^{-1}$ of $pp$ collisions at 7 TeV and 19.5 fb$^{-1}$ at 8 TeV. No significant signal was found. Upper limits on the number of signal events, with properties corresponding to those reported by D0, and on the $X$ production rate relative to $B^0_s$ mesons, $\rho_X$, were determined at 95% confidence level. The results are $N(X) < 382$ and $\rho_X < 0.015$ for $B^0_s$ mesons with transverse momenta above 10 GeV, and $N(X) < 356$ and $\rho_X < 0.016$ for transverse momenta above 15 GeV. Limits are also set for potential $B^0_s \pi^\pm$ resonances in the mass range 5550 MeV to 5700 MeV.