61 research outputs found
Measurement of the Analyzing Power in \\with a Fast Forward --Diproton
A measurement of the analyzing power of the
reaction was carried out at beam energies of 0.5 and 0.8 GeV by detection of a
fast forward proton pair of small excitation energy MeV. The
kinematically complete experiment made use of the ANKE spectrometer at the
internal beam of COSY and a deuterium cluster--jet target. For the first time
the --wave dominance in the fast diproton is experimentally demonstrated in
this reaction. While at GeV the measured analyzing power
vanishes, it reaches almost unity at GeV for neutrons scattered at
. The results are compared with a model taking into
account one--nucleon exchange, single scattering and (1232) excitation
in the intermediate state. The model describes fairly well the unpolarized
cross section obtained earlier by us and the analyzing power at 0.8 GeV, it
fails to reproduce the angular dependence of at 0.5 GeV.Comment: 4 pages, 4 figures, 1 tabl
Near-threshold production of omega mesons in the pn -> d omega reaction
The first measurement of the p n -> d omega total cross section has been
achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium
cluster-jet target. The momentum of the fast deuteron was measured in the ANKE
spectrometer at COSY-Juelich and that of the slow "spectator" proton p(sp) from
the p d -> p(sp) d omega reaction in a silicon telescope placed close to the
target. The cross sections lie above those measured for p p -> p p omega but
seem to be below theoretical predictions.Comment: 7 pages, 8 figures; second approach to describe the background has
been added; results changed insignificantly, EPJ in pres
a0+(980)-resonance production in pp->dK+Kbar0 reactions close to threshold
The reaction pp->d K+ Kbar0 has been investigated at an excess energy of Q=46
MeV above the (K+ Kbar0) threshold with ANKE at COSY-Juelich. From the detected
coincident dK+ pairs about 1000 events with a missing Kbar0 were identified,
corresponding to a total cross section of sigma(pp->d K+ Kbar0)=(38 +/- 2(stat)
+/- 14(syst)) nb. Invariant-mass and angular distributions have been jointly
analyzed and reveal s-wave dominance between the two kaons, accompanied by a
p-wave between the deuteron and the kaon system. This is interpreted in terms
of a0+(980)-resonance production.Comment: 4 pages, 4 figures; accepted by Phys. Rev. Let
Proton--induced deuteron breakup at GeV energies with forward emission of a fast proton pair
A study of the deuteron breakup reaction with forward emission
of a fast proton pair with small excitation energy 3 MeV has been
performed at the ANKE spectrometer at COSY--J\"ulich. An exclusive measurement
was carried out at six proton--beam energies ~0.6,~0.7,~0.8,~0.95,~1.35,
and 1.9 GeV by reconstructing the momenta of the two protons. The differential
cross section of the breakup reaction, averaged up to over the cm
polar angle of the total momentum of the pairs, has been obtained. Since
the kinematics of this process is quite similar to that of backward elastic scattering, the results are compared to calculations based on a
theoretical model previously applied to the process.Comment: 17 pages including 6 figures and 1 table v2: minor changes; v3: minor
change of author list; v4: changes in accordance with referee remark
Measurement of the decay form factors in the OKA experiment
A precise measurement of the vector and axial-vector form factors difference
in the decay is presented.
About 95K events of are selected in
the OKA experiment. The result is .
Both errors are smaller than in the previous measurements.Comment: 9 pages, 8 figure
Forward K+ production in subthreshold pA collisions at 1.0 GeV
K+ meson production in pA (A = C, Cu, Au) collisions has been studied using
the ANKE spectrometer at an internal target position of the COSY-Juelich
accelerator. The complete momentum spectrum of kaons emitted at forward angles,
theta < 12 degrees, has been measured for a beam energy of T(p)=1.0 GeV, far
below the free NN threshold of 1.58 GeV. The spectrum does not follow a thermal
distribution at low kaon momenta and the larger momenta reflect a high degree
of collectivity in the target nucleus.Comment: 4 pages, 3 figure
Polarization Effects in Exclusive Hyperon Production Reactions
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
DISTO: a large acceptance multiparticle spectrometer for 1–3 GeV proton beams
Abstract A magnetic spectrometer system has been constructed for the study of reactions with multiple charged particles in the final state, induced by polarized proton beams of few GeV energy. The system is based on a large-gap dipole magnet, with a liquid hydrogen target and scintillating fiber tracking detectors embedded inside the magnet. Multiwire proportional chambers, plastic scintillator hodoscopes, and threshold Cherenkov detectors placed outside the magnet provide additional tracking, triggering and particle identification capabilities. The system has been applied to study exclusive hyperon as well as pseudoscalar and vector meson production reactions at bombarding energies below 3 GeV. Additionally, it has been used to monitor the proton beam polarization at Laboratoire National Saturne. The components and performance of the system are reported
Searches for the light invisible axion-like particle in decay
A high statistics data sample of the decays is recorded by the OKA
collaboration. A missing mass analysis is performed to search for a light
invisible pseudoscalar axion-like particle (ALP) in the decay . No signal is observed, the upper limits for the branching
ratio of the decay are calculated. The confidence level upper limit is
changing from to for the ALP mass from 0 to
200 MeV/, except for the region of mass, where the upper limit
is .Comment: 6 pages, 6 figure
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