$D_{s0}(2590)$ as a dominant $c\bar{s}$ state with a small $D^{\ast }K$ component

Abstract

The recently discovered $D_{s0}(2590)$ state by the LHCb collaboration was regarded as the first excited state of ${}^1{S}_0$ charmed-strange meson. Its mass is, however, lower than the Godfrey-Isgur quark model prediction by about 80 MeV. In this work, we take into account the $D^{\ast }K$ contribution to the bare $c\bar{s}$ state, and show that the coupled-channel interaction induces an 88 MeV shift with respect to the conventional quark model $c\bar{s}$ state, which is much closer to the experimental mass. Our study shows that in addition to $S$-wave, $P$-wave coupled-channel interactions also play a role for hadrons located close to two-hadron thresholds. We further scrutinize the unquenched quark model results with a model independent approach. It is shown that the two-body $D^{\ast }K$ decay width is proportional to the weight of the $D^{\ast }K$ component. To saturate the experimental total decay width with the $D^{\ast }K$ partial decay width we need a weight of about 60\% while to reproduce the unquenched quark model result a weight of about 5\% is needed. Therefore, we encourage future experimental studies on the two-body $D^{\ast }K$ partial decay of $D_{s0}(2590)$.

13 pages, 1 figure