Search for a doubly-charged $DDK$ bound state in ${\rm Y}(1S,2S)$ inclusive decays and via direct production in $e^{+}{e}^{-}$ collisions at $\sqrt{s}$ = 10.520, 10.580, and 10.867 GeV

Abstract

We report the results of a first search for a doubly-charged $DDK$ bound state, denoted the $R^{++}$, in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ inclusive decays and via direct production in $e^{+}{e}^{-}$ collisions at $\sqrt{s}$ = 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 $D^{+}{D}_s^{\ast +}$ invariant-mass spectra of all studied modes. The 90\% credibility level upper limits on their product branching fractions in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ inclusive decays ($\mathcal{B}({\rm Y}(1S,2S)\to R^{++}+anything)\times \mathcal{B}(R^{++}\to D^{+}{D}_s^{\ast +})$), and the product values of Born cross section and branching fraction in $e^{+}{e}^{-}$ collisions ($\sigma (e^{+}{e}^{-}\to R^{++}+anything)\times \mathcal{B}(R^{++}\to D^{+}{D}_s^{\ast +})$) at $\sqrt{s}$ = 10.520, 10.580, and 10.867 GeV under different assumptions of $R^{++}$ masses varying from 4.13 to 4.17 GeV/$c^2$, and widths varying from 0 to 5 MeV are obtained.

14 pages, 11 figures, accepted for publication as a Regular Article in Physical Review D