166 research outputs found
Recommended from our members
Comparison of nanotubes produced by fixed bed and aerosol-CVD methods and their electrical percolation behaviour in melt mixed polyamide 6.6 composites
The electrical percolation behaviour of five different kinds of carbon nanotubes (CNTs) synthesised by two CVD techniques was investigated on melt mixed composites based on an insulating polyamide 6.6 matrix. The electrical percolation behaviour was found to be strongly dependent on the properties of CNTs which varied with the synthesis conditions. The lowest electrical percolation threshold (0.04 wt.%) was determined for as grown multi-walled carbon nanotubes without any purification or chemical treatment. Such carbon nanotubes were synthesised by the aerosol method using acetonitrile as ferrocene containing solvent and show relatively low oxygen content near the surface, high aspect ratio, and good dispersability. Similar properties could be found for nanotubes produced by the aerosol method using cyclohexane, whereas CNTs produced by the fixed bed method using different iron contents in the catalyst material showed much higher electrical percolation thresholds between 0.35 and 1.02 wt.%. © 2009 Elsevier Ltd. All rights reserved
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
Isospin dependence of the eta prime meson production in nucleon-nucleon collisions
A comparison of the close-to-threshold total cross section for the eta prime
production in pp --> pp eta prime and pn --> pn eta prime reactions constitutes
a tool to investigate the eta prime meson structure and the reaction mechanism
in the channels of isospin I=0 and I=1 and may provide insight into the
flavour-singlet (perhaps also into gluonium) content of the eta prime meson. In
this contribution we present preliminary results of measurement of the
quasi-free production of the eta prime meson in the proton-neutron collisions
conducted using the COSY-11 facility.Comment: Presented at 10th International Workshop on Meson Production,
Properties and Interaction (MESON 2008), Cracow, Poland, 6 - 10 June 200
Search for Bremsstrahlung radiation in quasi-free n p --> n p gamma reactions
Due to the high sensitivity of the N N --> N N gamma reaction to the
nucleon-nucleon potential, Bremsstrahlung radiation is used as a tool to
investigate details of the nucleon-nucleon interaction. Such investigations can
be performed at the cooler synchrotron COSY in the Research Centre Juelich, by
dint of the COSY-11 detection system. The results of the identification of
Bremsstrahlung radiation emitted via the d p --> d p gamma reaction in data
taken with a proton target and a deuteron beam are presented and discussed.Comment: 3 pages; Presented at Meson 2004: 8th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004;
Submitted to International Journal of Modern Physics
Production of Eta Mesons in Proton-Proton Collisions Close to Threshold
A brief experimental overview on the close-to-threshold eta meson production
in proton-proton interactions is presented and the available observables in
measurements with unpolarized and polarized beam and target are discussed.Comment: 4 pages; Presented at Meson 2004: 8th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004;
Submitted to International Journal of Modern Physics
Near threshold eta meson production in dp collisions
Preliminary results of recent measurements of the near threshold eta meson
production in the dp-->dp eta reaction are presented. The experiment was
performed at the COSY-Juelich accelerator with the use of the COSY-11 detection
system. Data were taken for three values of deuteron beam momenta corresponding
to excess energies of 3.2, 6.1 and 9.2 MeV. The energy dependence of the total
cross section confirms a strong effect of the final state interaction.Comment: Talk given at 9th International Workshop on Meson Production,
Properties and Interaction, Cracow, Poland, 9-13 June 2006. 5 pages, 3
figure
Absence of spin dependence in the final state interaction of the d(pol) p --> 3He eta reaction
The deuteron tensor analysing power t_{20} of the d(pol) p --> 3He eta
reaction has been measured at the COSY-ANKE facility in small steps in excess
energy Q up to Q = 11 MeV. Despite the square of the production amplitude
varying by over a factor of five through this range, t_{20} shows little or no
energy dependence. This is evidence that the final state interaction causing
the energy variation is not influenced by the spin configuration in the
entrance channel. The weak angular dependence observed for t_{20} provides
useful insight into the amplitude structure near threshold.Comment: 5 pages, 4 figure
New determination of the mass of the eta meson at COSY-ANKE
A value for the mass of the eta meson has been determined at the COSY-ANKE
facility through the measurement of a set of deuteron laboratory beam momenta
and associated 3He center-of-mass momenta in the d+p -> 3He+X reaction. The eta
was then identified by the missing-mass peak and the production threshold
determined. The individual beam momenta were fixed with a relative precision of
3 x 10^-5 for values around 3 GeV/c by using a polarized deuteron beam and
inducing an artificial depolarizing spin resonance, which occurs at a
well-defined frequency. The final-state momenta in the two-body d+p -> 3He+eta
reaction were investigated in detail by studying the size of the 3He momentum
ellipse with the forward detection system of the ANKE spectrometer. Final
alignment of the spectrometer for this high precision experiment was achieved
through a comprehensive study of the 3He final-state momenta as a function of
the center-of-mass angles, taking advantage of the full geometrical acceptance.
The value obtained for the mass, m(eta)=(547.873 +- 0.005(stat) +- 0.027(syst))
MeV/c^2, is consistent and competitive with other recent measurements, in which
the meson was detected through its decay products.Comment: 11 pages, 11 figures, 3 tables, published versio
Threshold Hyperon Production at COSY-11
The Lambda, Sigma0 and Sigma+ hyperon production in NN collisions is studied
at the COSY - 11 installation in order to investigate the production mechanism
as well as to extract information about the Y-N interaction.Comment: 3 pages, 2 figure
- …