74,015 research outputs found
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
Meson-production experiments at COSY-Juelich
Selected results from experiments at COSY-Juelich are presented: an attempt
to measure the mass of the eta meson with high precision (ANKE facility), first
steps towards the detection of rare eta decays (WASA), and several measurements
of KKbar-pair production (ANKE, COSY-11, MOMO).Comment: Proceedings of QNP2009, Beijing, Sept. 2009; to be published in
Chinese Physics C. 6 pages, 5 figure
Phenomenological studies of the low energy dynamics in the system
In this article we review studies of the near threshold
reaction done with the COSY-11 and ANKE detectors. We discuss phenomenological
studies of the dynamics, in particular the recent investigations on
the final state interaction are presented.Comment: Proceedings of the EFB22 conference (4 pages, 1 figure
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
Meson Production at COSY-TOF and COSY-ANKE
The roles of the COSY-TOF and COSY-ANKE spectrometers in the measurement of
strange meson production are briefly reviewed, mainly in connection with new
results on the pp -> K^+ p Lambda, pp -> K^+ p Sigma^0 and pp -> K^+ n Sigma^+
reactions.Comment: Invited talk at the MESON2010 conference in Krakow, June 201
Medium effects in pair production by 2.83 GeV protons on nuclei
We study pair production in the interaction of protons of 2.83
GeV kinetic energy with C, Cu, Ag, and Au target nuclei in the framework of the
nuclear spectral function approach for incoherent primary proton--nucleon and
secondary pion--nucleon production processes, and processes associated with the
creation of intermediate pairs. The approach accounts for the
initial proton and final hyperon absorption, final meson
distortion in nuclei, target nucleon binding, and Fermi motion, as well as
nuclear mean-field potential effects on these processes. We calculate the
momentum dependence of the absolute yield from the
target nuclei considered, in the kinematical conditions of the ANKE experiment,
performed at COSY, within the different scenarios for the -nucleus
effective scalar potential. We show that the above observable is appreciably
sensitive to this potential in the low-momentum region. Therefore, direct
comparison of the results of our calculations with the data from the
ANKE-at-COSY experiment can help to determine the above potential at finite
momenta. We also demonstrate that the two-step pion--nucleon production
channels dominate in the low-momentum production in the chosen
kinematics and, therefore, they have to be taken into account in the analysis
of these data.Comment: 29 page
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
Non-resonant kaon pair production and medium effects in proton-nucleus collisions
We study the non-resonant (non-) production of pairs by
protons of 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets within the
collision model, based on the nuclear spectral function, for incoherent primary
proton--nucleon and secondary pion--nucleon creation processes. The model takes
into account the initial proton and final kaon absorption, target nucleon
binding and Fermi motion as well as nuclear mean-field potential effects on
these processes. We calculate the antikaon momentum dependences of the
exclusive absolute and relative pair yields in the acceptance window
of the ANKE magnetic spectrometer, used in a recent experiment performed at
COSY, within the different scenarios for the antikaon-nucleus optical
potential. We demonstrate that the above observables are strongly sensitive to
this potential. Therefore, they can be useful to help determine the
optical potential from the direct comparison of the results of our calculations
with the data from the respective ANKE-at-COSY experiment. We also show that
the pion--nucleon production channels dominate in the low-momentum ,
production in the considered kinematics and, hence, they have to be accounted
for in the analysis of these data.Comment: 19 page
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