127 research outputs found
Experimental proton-proton correlation function derived for the pp -> ppeta reaction
Based on the high statistics data from the pp -> ppX reaction measured by the
COSY-11 collaboration [1] we have derived a two-proton correlation function for
the production of the ppeta and pp+pions systems. The measured correlation
function normalized to the value simulated for a point-like source was compared
with a theoretical prediction in order to estimate the size of the reaction
volume.Comment: Talk given at the Symposium on Meson Physics at COSY-11 and
WASA-at-COSY Krakow, Poland, 17-22 June 200
Determination of the total width of the eta' meson
Taking advantage of both the low-emittance proton-beam of the Cooler
Synchrotron COSY and the high momentum precision of the COSY-11 detector
system, the mass distribution of the eta' meson was measured with a resolution
of 0.33 MeV/c^2 (FWHM), improving the experimental mass resolution by almost an
order of magnitude with respect to previous results. Based on the sample of
more than 2300 reconstructed pp --> pp eta' events the total width of the eta'
meson was determined to be 0.226 +- 0.017(stat.) +- 0.014(syst.) MeV/c^2.Comment: 4 pages, 4 figure
Measurement of the invariant mass distributions for the pp -> ppeta' reaction at excess energy of Q = 16.4 MeV
The proton-proton and proton-eta' invariant mass distributions have been
determined for the pp -> ppeta' reaction at an excess energy of Q = 16.4 MeV.
The measurement was carried out using the COSY-11 detector setup and the proton
beam of the cooler synchrotron COSY. The shapes of the determined invariant
mass distributions are similar to those of the pp -> ppeta reaction and reveal
an enhancement for large relative proton-proton momenta. This result, together
with the fact that the proton-eta interaction is much stronger that the
proton-eta' interaction, excludes the hypothesis that the observed enhancement
is caused by the interaction between the proton and the meson
Upper limit of the total cross section for the pn --> pn eta' reaction
The upper limit of the total cross section for the pn --> pn eta' reaction
has been determined near the kinematical threshold in the excess energy range
from 0 to 24 MeV. The measurement was performed using the COSY-11 detector
setup, a deuteron cluster target, and the proton beam of COSY with a momentum
of 3.35 GeV/c. The energy dependence of the upper limit of the cross section
was extracted exploiting the Fermi momenta of nucleons inside the deuteron.
Comparison of the determined upper limit of the ratio R_eta' = sigma(pn --> pn
eta') / sigma(pp --> pp eta') with the corresponding ratio for eta-meson
production does not favor the dominance of the N*(1535) resonance in the
production process of the eta' meson and suggests nonidentical production
mechanisms for eta and eta' mesons
Determination of the eta'-proton scattering length in free space
Taking advantage of both the high mass resolution of the COSY-11 detector and
the high energy resolution of the low-emittance proton-beam of the Cooler
Synchrotron COSY we determine the excitation function for the pp --> pp eta'
reaction close-to-threshold. Combining these data with previous results we
extract the scattering length for the eta'-proton potential in free space to be
Re(a_{p eta'}) = 0+-0.43 fm and Im(a_{p eta'}) = 0.37(+0.40)(-0.16) fm.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
Isospin dependence of the eta' meson production in nucleon--nucleon collisions
According to the quark model, the masses of eta and eta' mesons should be
almost equal. However, the empirical values of these masses differ by more than
the factor of two. Similarly, though the almost the same quark-antiquark
content, the total cross section for the creation of these mesons close to the
kinematical thresholds in the pp --> ppX reaction differs significantly. Using
the COSY-11 detection setup we intend to determine whether this difference will
also be so significant in the case of the production of these mesons in the
proton-neutron scattering. Additionally, the comparison of the pp --> pp eta'
and pn --> pn eta' total cross sections will allow to learn about the
production of the eta' meson in the channels of isospin I = 0 and I = 1 and to
investigate aspects of the gluonium component of the eta' meson.Comment: Presented at LEAP05: International conference on Low Energy
Antiproton Physics, Bonn - Juelich, Germany, May 16-22, 200
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