Search for tetraquark states X-ccss in D-s(+) D-s(+) (D-s*(+) D-s*(+)) final states at Belle

A search for double-heavy tetraquark state candidates Xccs¯s¯ decaying to Ds+Ds+ and Ds∗+Ds∗+ is presented for the first time using the data samples of 102×106 ϒ(1S) and 158×106 ϒ(2S) events, and the data samples at s=10.52, 10.58, and 10.867 GeV corresponding to integrated luminosities of 89.5, 711.0, and 121.4 fb-1, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. The invariant-mass spectra of the Ds+Ds+ and Ds∗+Ds∗+ are studied to search for possible resonances. No significant signals are observed, and the 90% confidence level upper limits on the product branching fractions [B(ϒ(1S,2S)→Xccs¯s¯+anything)×B(Xccs¯s¯→Ds+Ds+(Ds∗+Ds∗+))] in ϒ(1S,2S) inclusive decays and the product values of Born cross section and branching fraction [σ(e+e-→Xccs¯s¯+anything)×B(Xccs¯s¯→Ds+Ds+(Ds∗+Ds∗+))] in e+e- collisions at s=10.52, 10.58, and 10.867 GeV under different assumptions of Xccs¯s¯ masses and widths are obtained.