Can X(5568) be described as a Bsπ, BK¯ resonant state?

AbstractThe D0 Collaboration has recently seen a resonant-like peak in the Bsπ invariant mass spectrum, claimed to be a new state called X(5568). Using a Bsπ–BK¯ coupled channel analysis, implementing unitarity, and with the interaction derived from Heavy Meson Chiral Perturbation Theory, we are able to reproduce the reported spectrum, with a pole that can be associated to the claimed X(5568) state, and with mass and width in agreement with the ones reported in the experimental analysis. However, if the T-matrix regularization is performed by means of a momentum cutoff, the value for the latter needed to reproduce the spectrum is Λ=2.80±0.04GeV, which is much larger than a “natural” value Λ≃1GeV. In view of this, it is difficult to interpret the nature of this new state. This state would not qualify as a resonance dynamically generated by the unitarity loops. Assuming the observed peak to correspond to a physical state, we make predictions for partners in the D, D⁎, and B⁎ sectors. Their observation (or lack thereof) would shed light into this issue