1,430 research outputs found
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
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
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
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 decays
We describe the -wave in decays using
a unitary model for the 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
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