Lowest lying even-parity ${\bar{B}}_s$ mesons: heavy quark spin-flavor symmetry, chiral dynamics, and constituent quark model bare masses

The discovery of the $D_{s0}^{\ast }(2317)$ and $D_{s1}(2460)$ resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between $Q\bar{q}$ and $(Q\bar{q})(q\bar{q})$ Fock components. In contrast to the $c\bar{s}$ sector, there is no experimental evidence of $J^P=0^{+},1^{+}$ bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the $D_{s0}^{\ast }(2317)$ and $D_{s1}(2460)$ states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark model P-wave ${\bar{B}}_s$ scalar and axial mesons and the ${\bar{B}}^{(\ast )}K$ channels is incorporated employing an effective interaction, consistent with heavy quark spin symmetry, constrained by the lattice energy levels.