Abstract
The total cross section of the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}p\overline{p}$ is calculated within the energy range close to the mass of $\ensuremath{\psi}(3770)$ charmonium state. It was shown that the main contribution to this cross section comes from three gluon mechanism which is also responsible of the large phase with respect to the Born amplitude. This phase provides the characteristic dip behavior of the cross section in contrast to the usual Breit-Wigner peak shape. Okubo--Zweig--Iizuka-allowed mechanism with $D$-mesons in the intermediate state was also estimated and gives relatively small contribution to the cross section and to the phase.
Highlights
The electron-positron colliders allow to study different physical processes with final particles in pure JPC 1⁄4 1−− state
The latter one [5] made precise measurement of the total cross section at the specific kinematics of ψð3770Þ mass and showed that instead of a Breit–Wigner peak one can see a dip in the dependence of the total invariant mass squared s
Soon some possible explanation of this phase was suggested in Ref. [6] where is was attributed to the OZI-violated three gluon mechanism of charmonium ψð3770Þ transition into final proton-antiproton state
Summary
The electron-positron colliders allow to study different physical processes with final particles in pure JPC 1⁄4 1−− state. One of the intriguing states of charmonium is ψð3770Þ which was studied by many collaborations (for example, by KEDR-VEPP-4M [1,2], CLEO [3] and more recently by BES III [4,5]) The latter one [5] made precise measurement of the total cross section at the specific kinematics of ψð3770Þ mass and showed that instead of a Breit–Wigner peak one can see a dip in the dependence of the total invariant mass squared s (see Fig. 2 in [5]). [6] where is was attributed to the OZI-violated three gluon mechanism of charmonium ψð3770Þ transition into final proton-antiproton state This type of mechanism was already shown to give large phase for another charmonium χ2ð3P2Þ in Ref. This type of mechanism was already shown to give large phase for another charmonium χ2ð3P2Þ in Ref. [7]: it was shown that two gluon mechanism can produce the phase of order of φ ∼ −90°
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