81 research outputs found
Spectator detection for the measurement of proton neutron interactions at ANKE
A telescope of three silicon detectors has been installed close to the
internal target position of the ANKE spectrometer, which is situated inside the
ultra-high vacuum of the COSY-Juelich light-ion storage ring. The detection and
identification of slow protons and deuterons emerging from a deuterium
cluster-jet target thus becomes feasible. A good measurement of the energy and
angle of such a spectator proton (p_sp) allows one to identify a reaction as
having taken place on the neutron in the target and then to determine the
kinematical variables of the ion-neutron system on an event-by-event basis over
a range of c.m. energies.
The system has been successfully tested under laboratory conditions. By
measuring the spectator proton in the p d to p_sp d pi^0 reaction in
coincidence with a fast deuteron in the ANKE Forward Detector, values of the p
n to d pi^0 total cross-section have been deduced. Further applications of the
telescope include the determination of the luminosity and beam polarisation
which are required for several experiments.Comment: 16 pages, 9 figure
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
The Polarized H and D Atomic Beam Source for ANKE at COSY-J\"ulich
A polarized atomic beam source was developed for the polarized internal
storage-cell gas target at the magnet spectrometer ANKE of COSY-J\"ulich. The
intensities of the beams injected into the storage cell, measured with a
compression tube, are hydrogen atoms/s (two hyperfine
states) and deuterium atoms/s (three hyperfine states). For
the hydrogen beam the achieved vector polarizations are . For the deuterium beam, the obtained combinations of vector
and tensor () polarizations are (with a
constant ), and or (both with vanishing ). The paper includes a detailed
technical description of the apparatus and of the investigations performed
during the development.Comment: 18 pages, 26 figures, 4 table
The neutron-proton charge-exchange amplitudes measured in the dp -> ppn reaction
The unpolarised differential cross section and the two deuteron tensor
analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange
reaction have been measured with the ANKE spectrometer at the COSY storage
ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were
obtained for small momentum transfers to a (pp) system with low excitation
energy. The results at the three lower energies are consistent with impulse
approximation predictions based upon the current knowledge of the
neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far
more uncertain, agreement requires a reduction in the overall double-spin-flip
contribution, with an especially significant effect in the longitudinal
direction. These conclusions are supported by measurements of the
deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were
carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The
values obtained for the proton analysing power also suggest the need for a
radical re-evaluation of the neutron-proton elastic scattering amplitudes at
the higher energy. It is therefore clear that such measurements can provide a
valuable addition to the neutron-proton database in the charge-exchange region.Comment: 13 pages with 13 figure
Study of the charge-exchange reaction using a polarised deuterium target
The vector and tensor analysing powers, and , of the charge-exchange reaction have been measured at a beam energy
of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam
incident on an internal storage cell target filled with polarised deuterium
gas. The low energy recoiling protons were measured in a pair of silicon
tracking telescopes placed on either side of the target. Putting a cut of 3 MeV
on the diproton excitation energy ensured that the two protons were dominantly
in the state, here denoted by . The polarisation of the
deuterium gas was established through measurements in parallel of
proton-deuteron elastic scattering. By analysing events where both protons
entered the same telescope, the charge-exchange reaction was measured for
momentum transfers MeV/. These data provide a good continuation
of the earlier results at MeV/ obtained with a polarised
deuteron beam. They are also consistent with impulse approximation predictions
with little sign evident for any modifications due to multiple scatterings
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
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
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
Machine studies for the development of storage cells at the ANKE facility of COSY
We present a measurement of the transverse intensity distributions of the
COSY proton beam at the target interaction point at ANKE at the injection
energy of 45 MeV, and after acceleration at 2.65 GeV. At 2.65 GeV, the machine
acceptance was determined as well. From the intensity distributions the beam
size is determined, and together with the measured machine acceptance, the
dimensions of a storage cell for the double-polarized experiments with the
polarized internal gas target at the ANKE spectrometer are specified. An
optimum storage cell for the ANKE experiments should have dimensions of 15mm x
20mm x 390mm (vertical x horizontal x longitudinal), whereby a luminosity of
about 2.5*10^29 cm^-2*s^-1 with beams of 10^10 particles stored in COSY could
be reached.Comment: 18 pages, 13 figures, 4 table
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
Simulation results for future measurements of electromagnetic proton form
factors at \PANDA (FAIR) within the PandaRoot software framework are reported.
The statistical precision with which the proton form factors can be determined
is estimated. The signal channel is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , is studied.
Furthermore, the background versus signal efficiency, statistical and
systematical uncertainties on the extracted proton form factors are evaluated
using two different procedures. The results are consistent with those of a
previous simulation study using an older, simplified framework. However, a
slightly better precision is achieved in the PandaRoot study in a large range
of momentum transfer, assuming the nominal beam conditions and detector
performance
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