Spectrum of the molecular tetraquarks: Unraveling the Tcs0(2900) and Tcas0(2900)

We relate the interactions of the over bar D(*)K* and D(*)K* systems to those of D(*)D(*) and D(*) over bar D(*) respectively, considering the residual strong interactions at the near -threshold energy is too weak to excite the strange quarks inside the hadrons. We propose an effective model to describe the low -energy S -wave interactions that are undertaken by the light u, d quarks between two separated heavy hadrons. We find that the existence of molecules in the heavy-(anti)heavy sectors will naturally lead to the emergence of molecular states in over bar D(*)K* and D(*)K* systems. The recently observed Tcs0(2900) and Tcas over bar 0(2900) can be well identified as the 0(0+) and 1(0+) partners of Tcc(3875) and Zc(3900) in the charmed strange sector, respectively. We also predict their members under the heavy (c and s) quark symmetry and SU(2) flavor symmetry. Most of them are very good molecule candidates, for example, (i) the 0(1+) states in D*D*, over bar DK*, over bar D*K*; (ii) the 0(+)(2+(+)) states in D* over bar D*, over bar D*K*, D*K*; (iii) the 1-(0++) state in D* over bar D* and 1(1+) state in D*K*. The 0+(0++) state in DD over bar and the 0(1+) state in DK* might also exist as virtual states, and the 0(1+) DK* can serve as a key to infer the existence of 0+(0++) D over bar D. The Ds pi invariant mass spectrum of Tcas over bar 0(2900) is also studied within the coupled -channel approach, and the molecular interpretation of Tcas over bar 0(2900) is consistent with the experimental data. Searching for the predicted states in experiments is crucial to discriminate the different pictures for interpreting these near -threshold exotica.