S. Wycech

Paris N N ¯ potential constrained by recent antiprotonic-atom data and n ¯ p total cross sections

We report on an updated Paris nucleon-antinucleon optical potential. The long- and intermediate-range real parts are obtained by G-parity transformation of the Paris nucleon-nucleon potential based on a theoretical dispersion-relation treatment of the correlated and uncorrelated two-pion exchange. The short-range imaginary potential parametrization results from the calculation of the nucleon-antinucleon annihilation box diagram into two mesons with a nucleon-antinucleon intermediate state in the crossed channel. The parametrized real and imaginary short range parts are determined by fitting not only the existing experimental data included in the 1999 version of the Paris nucleon-antinucleon potential, but also the recent antiprotonic-hydrogen data and antineutron-proton total cross sections. The description of these new observables is improved. Only this readjusted potential generates an isospin zero 1S0, 52 MeV broad quasibound state at 4.8 MeV below the threshold. Recent BES data on J/psi decays could support the existence of such a state.

On the structure of the X(1835) baryonium

The measurement by the BES Collaboration of J/{psi} {yields} {gamma}p{bar p} decays indicates an enhancement at the p{bar p} threshold. In another experiment, BES finds a peak in the invariant mass of {pi} mesons produced in the possibly related decay J/{psi} {yields} {gamma}{pi}{sup +}{pi}{sup -}{eta}{prime}. Using a semiphenomenological potential model that describes all the N{bar N} scattering data, we show that the explanation of both effects may be given by a broad quasibound state in the spin and isospin singlet S wave. The structure of the observed peak is due to an interference of this quasibound state with a background amplitude and depends on the annihilation mechanism.

Baryonium, a common ground for atomic and high energy physics

Indications of the existence of quasi-bound states in the NN¯

The N̄N quasi‐bound states: J/ψ and atomic evidence

N {\overline N}

Electromagnetic corrections to π−p scattering length from pionic hydrogen

system are presented. In their measurements, the BES collaboration has discoverd a broad enhancement close to the pp¯

Photon or meson formation in J/ψ decays into pp¯

p {\overline p}

Search for baryonium and the physics at FAIR

threshold in the S wave, isospin 0 state formed in radiative decays of J/ψ. Another enhancement located about 50 MeV below the threshold was found in mesonic decays of J/ψ. In terms of the Paris potential model it was shown that these are likely to represent the same state. Antiprotonic atomic data provide some support for this interpretation and indicate the existence of another fairly narrow quasi-bound state in a P wave.

The N-barN quasi-bound states: J/{psi} and atomic evidence

The measurements of J/{psi} decays into {gamma}pp-barshow a strong enhancement at pp-barthreshold not seen in the decays into {pi}0pp-bar. What is the nature of this enhancement? A natural interpretation can be performed in terms of a classical model of NN-barinteractions based on G-parity transformation. The observed pp-barstructure is the consequence of the strong attraction in the 1S0 state related predominantly to {pi}-meson exchanges. Similar attractions generate near threshold: a virtual (or quasi-bound) state in 11S0-, a quasi-bound state in 33P1- and a resonance in 13P0-waves. These P-wave structures find support in the p-bar-atomic data.

Phenomenological value of the πΛΣ coupling

We derive a closed, model space independent, expression for the electromagnetic correction factor

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