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Possible Mechanism for Understanding the Near Threshold Enhancement in J/ψ → γ pp

Possible Mechanism for Understanding the Near Threshold Enhancement in J/ψ → γ pp. Xiao-Hai Liu Institute of High Energy Physics, CAS. Collaborators: Qiang Zhao, Yuan-Jiang Zhang (Phys. Rev. D 80, 034032, 2009). Near Threshold Enhancement in J/ψ → γ pp (BESII results).

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Possible Mechanism for Understanding the Near Threshold Enhancement in J/ψ → γ pp

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  1. Possible Mechanism for Understanding the Near Threshold Enhancement in J/ψ→γpp Xiao-Hai Liu Institute of High Energy Physics, CAS Collaborators: Qiang Zhao, Yuan-Jiang Zhang (Phys. Rev. D 80, 034032, 2009)

  2. Near Threshold Enhancement in J/ψ→γpp(BESII results) M= 1859 MeV Γ< 30 MeV JPC=0-+ χ2/d.o.f.=56.3/56 Phys. Rev. Lett. 91, 022001

  3. Interpretations on this Phenomenon • Glueball candidate (Kochelev & Min; B.A. Li; Hao et al.; … ) • Baryonium (Datta & O’Donnell; Ding & Yan; Loiseau & Wycech; Zhu & Gao; …) • Final states pp interactions (Zou & Chiang; Kerbikov et al.; Bugg; Sibirtsev et al.; Entem & Fernandez; Chen et al.; …)

  4. Motivations of Considering VV Rescatering • The VV invariant mass distribution is dominated by the 0- components in J/ψ→γVV, and most of these channels have relatively larger branching ratios. (PLB 353, 378; PRD 73, 112007; PLB 472, 200; PRD 33, 1222; PRD 39, 701.) A very broad 0- resonance observed by BES, M=1800 MeV • These vector mesons generally have strong couplings with the nucleons and/or hyperons.

  5. The Model Suppressed Free Parameters Insignificant

  6. Numerical Fitting Results Model dependent parameters: • '1.15»1.20 GeV ', ' -/2 Destructive interferences

  7. Cross Section of pp→VV • In the experiments of pp annihilations at rest, i.e. pLab=200 Mev/c2, Crystal Barrel Collaboration, 1993 C. Baltay et al., 1963 • With the same effective Lagrangians, form factors and coupling constants as in J/ψ→γpp, • We didn’t overestimate the contributions of VV → pp

  8. Results for J/ψ→pp We could only do a rough estimation according to BESII result (PRD77, 032005) The corresponding parameters are taken the same as those in J/ψ→pp

  9. How to understand some other channels No significant enhancement BESII, 2007 CLEO, 2005

  10. How to understand some other channels • There is no significant narrow threshold enhancement in these two channels. • The pp FSI which fits the data of J/ψ→γpp will confront problems here, however it needs a more accurate experimental data as a premise. • Because of lack of the data for and some other related channels, our rescattering mechanism still needs to be checked in these processes.

  11. Summary and Outlook • The VV-rescattering effects, i.e. J/ψ→ γVV→γpp , may one of the possible mechanisms which can produce the near threshold enhancement observed by BESII in J/ψ→ γpp . • The fitting result indicates that the enhancement may be resulted from the destructive interference between different rescattering amplitudes. • The forthcoming BESIII results on J/ψ(ψ’)→ γpp and J/ψ(ψ’)→pp may help us to clarify this phenomenon and the underlying mechanism.

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