Abstract
We report the results of a first search for a doubly-charged $DDK$ bound state, denoted the $R^{++}$, in $\Upsilon(1S)$ and $\Upsilon(2S)$ 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 $D^{+}D_{s}^{*+}$ invariant-mass spectra of all studied modes. The 90\% credibility level upper limits on their product branching fractions in $\Upsilon(1S)$ and $\Upsilon(2S)$ inclusive decays (${\cal B}(\Upsilon(1S,2S) \to R^{++} + anything) \times {\cal B}(R^{++} \to D^{+} D_{s}^{*+})$), and the product values of Born cross section and branching fraction in $e^+e^-$ collisions ($\sigma(e^+e^- \to R^{++} + anything) \times {\cal B}(R^{++} \to D^{+} D_{s}^{*+})$) 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.
Highlights
In 2003, a narrow resonance near 2.32 GeV=c2, the DÃs0ð2317Þþ, was observed by BABAR [1] via its decay to Dþs π0
We report the results of a first search for a Υð1SÞ and Υð2SÞ inclusive decays and via ddioruecbtlyprcohdaurgcetidonDiDnKeþbeo−uncdollsitsaitoen, sdeant opteffisffid1⁄4th1e0R.5þ2þ0, 10.580, and 10.867 GeV
The observed low mass and narrow width of the DÃs0ð2317Þþ strongly disfavor the interpretation of this state as a P-wave csstate, both in potential model [4–9] and lattice Quantum Chromodynamics (QCD) [10,11] descriptions
Summary
In 2003, a narrow resonance near 2.32 GeV=c2, the DÃs0ð2317Þþ, was observed by BABAR [1] via its decay to Dþs π0. Inclusion of charge-conjugate decays is implicitly assumed throughout this analysis Instead, it has been proposed as a possible candidate for a DK molecule [12–17], a ðcqÞðsq ̄ Þ tetraquark state [18–20], or a mixture of a csstate and tetraquark [21–28]. The Rþþ can be interpreted as a DþDÃs0ð2317Þþ moleculelike state with exotic properties: doubly charged and doubly charmed. [42], the authors predicted the existence of novel narrow doubly heavy tetraquark states of the form QQqqwith the method based on the heavy-quark symmetry and found that a doubly charmed tetraquark with a mass of 4156 MeV=c2 and a JP of 1þ decaying into a final state of DþDÃsþ can be formed. We report a search for the Rþþ with masses varying from 4.13 to 4.17 GeV=c2 and widths varying from 0 to 5 MeV
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