The antinucleon-nucleon quasi-bound states: J/psi and atomic evidence

The measurements of J/psi decays into photon, proton and antiproton show a strong enhancement at the proton-antiproton threshold not seen in the decays into neutral pion, proton and antiproton. What is the nature of this enhancement? A natural interpretation can be performed in terms of a classical model of nucleon-antinucleon interactions based on G-parity transformation. The observed proton-antiproton structure is the consequence of the strong attraction in the singlet S-wave state related predominantly to pion exchanges. Similar attractions generate near threshold: an isospin-zero virtual (or quasi-bound) state in singlet S-wave, an isospin-one quasi-bound state in triplet P-wave with total angular momentum one and an isospin-zero resonance in triplet P-wave with total angular momentum zero. These P-wave structures find support in the antiproton-atomic data.Comment: 7 pages, 3 eps figures. Invited talk (S. Wycech) to the International Conference on Low Energy Antiproton Physics (LEAP05), May 16-22, 2005, Bonn-Juelich, Germany, to appear in AIP series of conference proceeding

Peculiarities in multichannel interaction amplitudes for meson-meson scattering and scalar meson spectroscopy

Interactions in coupled channels pipi, KKbar and an effective 2pi2pi in scalar-isoscalar wave have been analysed. Influence of interchannel couplings on analytical structure of multichannel interaction amplitudes has been studied. Interplay of S-matrix zeroes and poles and their relation with parameters of scalar resonances has been investigated.Comment: presented by R. Kaminski at the Meson 2000 Conference, Cracow, Poland, May 19-23, 2000; 5 pages including 2 figures, to appear in Acta Physica Polonica

Roy's equations and the pion-pion experimental data

Roy's equations are used to check if the scalar-isoscalar pion-pion scattering amplitudes fitted to experimental data fulfill crossing symmetry conditions. It is shown that the amplitudes describing the ``down-flat'' phase shift solution satisfy crossing symmetry below 1 GeV while the amplitudes fitted to the "up-flat'' data do not. In this way the long standing "up-down" ambiguity in the phenomenological determination of the scalar-isoscalar pion-pion amplitudes has been resolved confirming the independent result of the recent joint analysis of the pi+pi- and pi0pi0 data.Comment: 6 pages, 2 figures, talk given at Tenth International Conference on Hadron Spectroscopy (Hadron'03), Aschaffenburg, Germany, August 31 - September 6 200

Analysis of New Results For Scalar-Isoscalar pi-pi Phase Shifts

The scalar -- isoscalar pi-pi phase shifts are analysed using a separable potential model of three coupled channels (pipi, KK and an effective 2pi2pi system). Model parameters are fitted to two sets of solutions obtained in a recent analysis of the CERN-Cracow-Munich measurements of the pi^- p --> pi^+ pi^- n reaction on a polarized target. A relatively narrow (90 -- 180 MeV) scalar resonance f_0(1400-1460) is found, together with a wide f_0(500) (Gamma = 500 MeV) and the narrow f_0(980) state.Comment: 4 pages, 3 figures. Talk given at 7th International Conference on Hadron Spectroscopy (Hadron 97), Upton, NY, 25-30 Aug 199

Multichannel Interaction Analysis of Scalar Mesons Below 1800 MeV

Properties of scalar--isoscalar mesons in a mass range from pi-pi threshold up to 1800 MeV are analysed using an unitary model with separable interactions in three decay channels: pi-pi, K-anti K and an effective 2pi-2pi. Different solutions are obtained by fitting pi-pi and K-anti K data. Analytical structure of the meson-meson multichannel amplitudes is studied with a special emphasis on the important role played by the S-matrix zeroes. The dependence of the positions of S-matrix singularities on the interchannel coupling strength is investigated. Poles, located in the complex energy plane not too far from the physical region, are interpreted as scalar resonances: a wide f0(500), a narrow f0(980) and a relatively narrow f0(1400). In all our solutions two resonances, lying on different sheets, in the energy region between 1300 MeV and 1500 MeV are found. These states may be compared with the resonances f0(1370) and f0(1500) seen in the experiments at CERN. Total, elastic and inelastic channel cross sections, branching ratios and coupling constants are evaluated and compared with available data.Comment: Talk given at Workshop on Hadron Spectroscopy, Frascati (Rome) - Italy, March 8-12, 1999. To be published in Frascati Physics Series, 8 pages, 4 figures, included file frascatiphys.st

pi-pi scattering amplitudes constrained by Roy's equations

The scalar-isoscalar, scalar-isotensor and vector-isovector pi-pi amplitudes have been fitted simultaneously to experimental data and to to Roy's equations. Resulting pi-pi phase shifts up to 1600 MeV and near threshold observables have been analyzed. Only the amplitudes fitted to the "down-flat" set of phase shifts in scalar-isoscalar wave fulfill crossing symmetry conditions and can be regarded as physical.Comment: 4 pages, talk presented at 12th International QCD Conference (QCD05) 4-9th July 2005 Montpellier (France), to appear in Nucl. Phys. B (Proc. Suppl.

Baryonium, a common ground for atomic and high energy physics

Indications of the existence of quasi-bound states in the N-Nbar system are presented. Measurements by BES discovered a broad enhancement close to the p-pbar threshold in the S wave, isospin 0 state formed in radiative decays of J/psi. Another enhancement located about 50 MeV below the threshold was found in mesonic decays of J/psi. 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.Comment: 6 pages, 6 figures - Contribution to EXA2014 Vienna to appear in a special edition of Hyperfine Interaction

On the structure of the X(1835) baryonium

The measurement by the BES collaboration of J/psi -> gamma p pbar decays indicates an enhancement at the p-pbar threshold. In another experiment BES finds a peak in the invariant mass of pi-mesons produced in the possibly related decay J/psi -> gamma pi+ pi- eta'. Using a semi-phenomenological potential model which describes all the N-Nbar scattering data, we show that the explanation of both effects may be given by a broad quasi-bound state in the spin and isospin singlet S wave. The structure of the observed peak is due to an interference of this quasi-bound state with a background amplitude and depends on the annihilation mechanism.Comment: 7 pages, 7 figures, this version corresponds to the published paper in Phys. Rev. C: minor corrections done and in section 5 suggestions of experiments to confirm the link of the X(1835) to the antiproton-proton syste

Resonances and weak interactions in D+→π+π−π+D^+ \to\pi^+ \pi^- \pi^+ decays

We describe the $\pi\pi$ $S$-wave in $D^+ \to\pi^+ \pi^- \pi^+$ decays using a unitary model for the $\pi\pi$ Final State Interactions (FSI). The three body decay is treated as a quasi two-body process where, at the weak vertex, the D meson decays into a resonance and a pion. The weak part of the decay amplitude is evaluated using the effective weak Hamiltonian within the factorization approximation.Comment: 4 pages. Contribution to the X Hadron Physics, Florianopolis-Brazil, March 26-31, 200