139 research outputs found
Small-angle X-ray scattering investigation of the pore structure of nuclear filters
Different types of nuclear filters were investigated by means of small-angle X-ray scattering. The distribution functions of the cross-sectional squares were calculated. The obtained results are in good agreement with the data of other physical-chemical methods. Small-angle scattering is found to be effective for structural investigations of nuclear filters
Resonance-like coherent production of a pion pair in the reaction in the GeV region
The reaction was studied at 0.8-2.0 GeV proton
beam energies with the ANKE magnetic spectrometer at the COSY synchrotron
storage ring. The proton-deuteron pairs emerging with high momenta, 0.6-1.8
GeV/, were detected at small angles with respect to the proton beam.
Distribution over the reaction missing mass reveals a local enhancement
near the threshold of the pion pair production specific for the so-called ABC
effect. The enhancement has a structure of a narrow bump placed above a smooth
continuum. The invariant mass of the system in this enhancement
region exhibits a resonance-like peak at GeV/
with the width GeV/. A possible interpretation of
these features is discussed.Comment: 14 pages, 16 figures, submitted to Eur. Phys. J. A. v2: Added
references [42,43] in section IV.A. v3: revised version according to referee
remarks v4: revised version according to referee remark
First measurements of spin correlations in the np -> d pi^0 reaction
The transverse spin correlations Axx and Ayy in the np-> d pi^0 reaction have
been measured for the first time in quasi-free kinematics at the COSY-ANKE
facility using a polarised deuteron beam incident on a polarised hydrogen cell
target. The results obtained for neutron energies close to 353 MeV and 600 MeV
are in good agreement with the partial wave analysis of data on the
isospin-related pp-> d pi^+ reaction, though the present results cover also the
small-angle region, which was largely absent from these data
Coherent pion production in proton-deuteron collisions
Values of the proton analysing power in the
reactions at 350-360~MeV
per nucleon were obtained by using a polarised proton beam incident on a
deuterium cluster-jet target and with a polarised deuteron beam incident on a
target cell filled with polarised hydrogen. These results have a much larger
angular coverage than existing data. First measurements are also presented of
the deuteron vector analysing power and the deuteron-proton spin correlations.
Data were also obtained on the deuteron-proton spin correlation and proton
analysing power at small angles at 600~MeV per nucleon, though the angular
coverage at this energy was much more restricted even when using a deuteron
beam. By combining the extrapolated values of the spin correlations to the
forward or backward directions with published measurements of the deuteron
tensor analysing powers, the relative phases between the two non-vanishing
amplitudes were evaluated.Comment: 5 pages, 5 figure
Measurement of the analyzing powers in pd elastic and pn quasi-elastic scattering at small angles
The analyzing powers in proton-deuteron elastic and proton-neutron
quasi-elastic scattering have been measured at small angles using a polarized
proton beam at the COSY storage ring incident on an unpolarized deuterium
target. The data were taken at 796MeV and five higher energies from 1600MeV to
2400MeV. The analyzing power in pd elastic scattering was studied by detecting
the low energy recoil deuteron in telescopes placed symmetrically in the COSY
plane to the left and right of the beam whereas for pn quasi-elastic scattering
a low energy proton was registered in one of the telescopes in coincidence with
a fast scattered proton measured in the ANKE magnetic spectrometer. Though the
experiment explores new domains, the results are consistent with the limited
published information.Comment: 10 pages with 8 figure
Measuring the Polarization of a Rapidly Precessing Deuteron Beam
This paper describes a time-marking system that enables a measurement of the
in-plane (horizontal) polarization of a 0.97-GeV/c deuteron beam circulating in
the Cooler Synchrotron (COSY) at the Forschungszentrum J\"ulich. The clock time
of each polarimeter event is used to unfold the 120-kHz spin precession and
assign events to bins according to the direction of the horizontal
polarization. After accumulation for one or more seconds, the down-up
scattering asymmetry can be calculated for each direction and matched to a
sinusoidal function whose magnitude is proportional to the horizontal
polarization. This requires prior knowledge of the spin tune or polarization
precession rate. An initial estimate is refined by re-sorting the events as the
spin tune is adjusted across a narrow range and searching for the maximum
polarization magnitude. The result is biased toward polarization values that
are too large, in part because of statistical fluctuations but also because
sinusoidal fits to even random data will produce sizeable magnitudes when the
phase is left free to vary. An analysis procedure is described that matches the
time dependence of the horizontal polarization to templates based on
emittance-driven polarization loss while correcting for the positive bias. This
information will be used to study ways to extend the horizontal polarization
lifetime by correcting spin tune spread using ring sextupole fields and thereby
to support the feasibility of searching for an intrinsic electric dipole moment
using polarized beams in a storage ring. This paper is a combined effort of the
Storage Ring EDM Collaboration and the JEDI Collaboration.Comment: 28 pages, 15 figures, prepared for Physical Review ST - Accelerators
and Beam
Analysing powers and spin correlations in deuteron-proton charge exchange at 726 MeV
The charge exchange of vector polarised deuterons on a polarised hydrogen
target has been studied in a high statistics experiment at the COSY-ANKE
facility at a deuteron beam energy of Td = 726 MeV. By selecting two fast
protons at low relative energy E_{pp}, the measured analysing powers and spin
correlations are sensitive to interference terms between specific
neutron-proton charge-exchange amplitudes at a neutron kinetic energy of Tn ~
1/2 Td =363 MeV. An impulse approximation calculation, which takes into account
corrections due to the angular distribution in the diproton, describes
reasonably the dependence of the data on both E_{pp} and the momentum transfer.
This lends broad support to the current neutron-proton partial-wave solution
that was used in the estimation
Measurement of the analysing power in proton-proton elastic scattering at small angles
The proton analysing power in elastic scattering has been measured
at small angles at COSY-ANKE at 796 MeV and five other beam energies between
1.6 and 2.4 GeV using a polarised proton beam. The asymmetries obtained by
detecting the fast proton in the ANKE forward detector or the slow recoil
proton in a silicon tracking telescope are completely consistent. Although the
analysing power results agree well with the many published data at 796 MeV, and
also with the most recent partial wave solution at this energy, the ANKE data
at the higher energies lie well above the predictions of this solution at small
angles. An updated phase shift analysis that uses the ANKE results together
with the World data leads to a much better description of these new
measurements.Comment: 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
Measurement of the absolute differential cross section of proton-proton elastic scattering at small angles
The differential cross section for proton-proton elastic scattering has been
measured at a beam energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV
for centre-of-mass angles in the range from 12-16 degrees to 25-30 degrees,
depending on the energy. Absolute normalisations of typically 3% were achieved
by studying the energy losses of the circulating beam of the COSY storage ring
as it passed repeatedly through the windowless hydrogen target of the ANKE
magnetic spectrometer. It is shown that the data have a significant impact upon
a partial wave analysis. After extrapolating the differential cross sections to
the forward direction, the results are broadly compatible with the predictions
of forward dispersion relations
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