Observation of a Charmoniumlike State Produced in Association with a<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi></mml:math>in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math>Annihilation at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>≈</mml:mo><mml:mn>10.6</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi></mml:math>
Аннотация
We report the first observation of a charmoniumlike state recoiling from the $J/\ensuremath{\psi}$ in the inclusive process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}+\mathrm{\text{anything}}$ at a mass of $(3.943\ifmmode\pm\else\textpm\fi{}0.006\ifmmode\pm\else\textpm\fi{}0.006)\text{ }\text{ }\mathrm{GeV}/{c}^{2}$. We also observe the decay of this state into ${D}^{*}\overline{D}$ and determine its intrinsic width to be less than $52\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ at the 90% C.L. These results are obtained from a $357\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample collected with the Belle detector near the $\ensuremath{\Upsilon}(4S)$ resonance, at the KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider.
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