Strange molecular partners of the Zc(3900) and Zc(4020)

摘要

Quantum chromodynamics presents a series of exact and approximate symmetries which can be exploited to predict new hadrons from previously known ones. The Z c ( 3900 ) and Z c ( 4020 ) , which have been theorized to be isovector D * D ˉ and D * D ˉ * molecules [ I G ( J P C ) = 1 ? ( 1 + ? ) ], are no exception. Here we argue that from SU(3)-flavor symmetry, we should expect the existence of strange partners of the Z c ’s with hadronic molecular configurations D * D ˉ s ? D D ˉ s * and D * D ˉ s * (or, equivalently, quark content c c ˉ s q ˉ , with q = u , d ). The quantum numbers of these Z c s and Z c s * structures would be I ( J P ) = 1 2 ( 1 + ) . The predicted masses of these partners depend on the details of the theoretical scheme used, but they should be around the D * D ˉ s ? D D ˉ s * and D * D ˉ s * thresholds, respectively. Moreover, any of these states could be either a virtual pole or a resonance. We show that, together with a possible triangle singularity contribution, such a picture nicely agrees with the very recent BESIII data of the e + e ? → K + ( D s ? D * 0 + D s * ? D 0 ) .