Search for a doubly charged DDK bound state in Υ(1S, 2S) inclusive decays and via direct production in e⁺e⁻ collisions at √s = 10.520, 10.580, and 10.867 GeV
We report the results of a first search for a doubly-charged DDK bound state, denoted the R++, in Υ(1S) and Υ(2S) inclusive decays and via direct production in e+e− collisions at s = 10.520, 10.580, and 10.867 GeV. The search uses data accumulated with the Belle detector at the KEKB asymmetric-energy e+e− collider. No significant signals are observed in the D+Ds∗+ invariant-mass spectra of all studied modes. The 90\% credibility level upper limits on their product branching fractions in Υ(1S) and Υ(2S) inclusive decays (B(Υ(1S,2S)→R+++ anything)×B(R++→D+Ds∗+)), and the product values of Born cross section and branching fraction in e+e− collisions (σ(e+e−→R+++ anything)×B(R++→D+Ds∗+)) at s = 10.520, 10.580, and 10.867 GeV under different assumptions of R++ masses varying from 4.13 to 4.17 GeV/c2, and widths varying from 0 to 5 MeV are obtained