13 research outputs found
Measurement of the Eta Production in Proton Proton Collisions with the COSY Time of Flight Spectrometer
The reaction pp -> pp eta was measured at excess energies of 15 and 41 MeV at
an external target of the Juelich Cooler Synchrotron COSY with the Time of
Flight Spectrometer. About 25000 events were measured for the excess energy of
15 MeV and about 8000 for 41 MeV. Both protons of the process pp eta were
detected with an acceptance of nearly 100% and the eta was reconstructed by the
missing mass technique. For both excess energies the angular distributions are
found to be nearly isotropic. In the invariant mass distributions strong
deviations from the pure phase space distributions are seen.Comment: 15 pages, 14 figures, 4 table
Cross section of the reaction close to threshold
We have measured inclusive data on -meson production in collisions
at COSY J\"ulich close to the hyperon production threshold and determined the
hyperon-nucleon invariant mass spectra. The spectra were decomposed into three
parts: , and . The cross section for the
channel was found to be much smaller than a previous measurement in
that excess energy region. The data together with previous results at higher
energies are compatible with a phase space dependence.Comment: accepted by Phys. lett. B some typos correcte
High resolution study of the Lambda p final state interaction in the reaction p + p -> K+ + (Lambda p)
The reaction pp -> K+ + (Lambda p) was measured at Tp=1.953 GeV and Theta = 0
deg with a high missing mass resolution in order to study the Lambda p final
state interaction. The large final state enhancement near the Lambda p
threshold can be described using the standard Jost-function approach. The
singlet and triplet scattering lengths and effective ranges are deduced by
fitting simultaneously the Lambda p invariant mass spectrum and the total cross
section data of the free Lambda p scattering.Comment: submitted to Physics Letters B, 10 pages, 3 figure
Improved study of a possible Theta+ production in the pp -> p K0 sigma+ reaction with the COSY-TOF spectrometer
The pp -> p K0 Sigma+ reaction was investigated with the TOF spectrometer at
COSY at 3.059 GeV/c incident beam momentum. The main objective was to clarify
whether or not a narrow exotic S = +1 resnance, the Theta+ pentaquark, is
populated at 1.53 GeV/c2 in the K0 p subsystem with a data sample of much
higher statistical significance compared to the previously reported data in
this channel. An analysis of these data does not confirm the existence of the
Theta+ pentaquark. This is expressed as an upper limit for the cross section
sigma (pp -> p K0 Sigma+) < 0.15 microbarn at the 95 percent confidence level.Comment: 11 pages, 5 figure
Influence of N*-resonances on hyperon production in the channel pp->K+ Lambda p at 2.95, 3.20 and 3.30 GeV/c beam momentum
Hyperon production in the threshold region was studied in the reaction pp ->
K+Lp using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering
the full phase-space, were taken at the three different beam momenta of
p_beam=2.95, 3.20 and 3.30 GeV/c, corresponding to excess energies of
epsilon=204, 285 and 316 MeV, respectively. Total cross-sections were deduced
for the three beam momenta to be 23.9+/-0.8 +/-2.0 ub, 28.4+/-1.3 +/-2.2 ub and
35.0+/-1.3 +/-3.0 ub. Differential observables including Dalitz plots were
obtained. The analysis of the Dalitz plots reveals a strong influence of the
N(1650)-resonance at p_beam=2.95 GeV/c, whereas for the higher momenta an
increasing relative contribution of the N(1710)- and/or of the
N(1720)-resonance was observed. In addition, the pL-final-state interaction
turned out to have a significant influence on the Dalitz plot distribution.Comment: accepted for publication at Physics Letters B; some minor text
changes were done; also the scale of the ordinates of figure 9 has been
changed