2,885 research outputs found
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
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 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
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 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
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
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
The CMS RPC gas gain monitoring system: an overview and preliminary results
The status of the CMS RPC Gas Gain Monitoring (GGM) system developed at the
Frascati Laboratory of INFN (Istituto Nazionale di Fisica Nucleare) is reported
on. The GGM system is a cosmic ray telescope based on small RPC detectors
operated with the same gas mixture used by the CMS RPC system. The GGM gain and
efficiency are continuously monitored on-line, thus providing a fast and
accurate determination of any shift in working point conditions. The
construction details and the first result of GGM commissioning are described.Comment: 8 pages, 9 figures, uses lnfprepCMS.sty, presented by L. Benussi at
RPC07, Mumbai, INDIA 200
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