With the ANKE spectrometer at the COoler SYnchrotron COSY Juelich the mesonic structure of the nucleon will be studied in polarized proton-proton and proton-deuteron collisions. The identification ...and tracking of low energy protons permits using deuterium as an effective neutron target. For this purpose, modular self-triggering tracking telescopes built up by double-sided silicon strip detectors inside the accelerator ultra-high vacuum have been developed. Their basic features are /spl Delta/E/E proton identification from 2.5 40 MeV and particle tracking over a wide dynamic range, either 2.5 MeV spectator protons or minimum ionizing particles. By the use of self-triggering read-out chips, the telescopes identify a particle passage within 100 ns and therefore allow the possibility of a fast hit pattern recognition. In combination with a read-out pitch of /spl sim/200 /spl mu/m, they provide a high rate capability. The recent development of very thick (/spl ges/5 mm) double-sided microstructured Si(Li) and very thin (/spl les/65 /spl mu/m) double-sided Si-detectors provides the use of the telescopes over a wide range of particle energies.
Determination of deuteron beam polarizations at COSY Chiladze, D.; Kacharava, A.; Rathmann, F. ...
Physical review special topics. PRST-AB. Accelerators and beams,
05/2006, Letnik:
9, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The vector and tensor polarizations of a deuteron beam have been measured using elastic deuteron-carbon scattering at 75.6 MeV and deuteron-proton scattering at 270 MeV. After their acceleration to ...1170 MeV inside the COSY ring, the polarizations of the deuterons were checked by studying a variety of nuclear reactions using a cluster target at the ANKE magnet spectrometer placed at an internal target position of the storage ring. All these measurements were consistent with the absence of depolarization during acceleration and provide us with a number of secondary standards that can be used in subsequent experiments at the facility.
Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The ...dependence of the cross section on the azimuthal angles of the target polarization (ϕS) and the produced hadron (ϕ) is found to have a substantial sin(ϕ+ϕS) modulation for the production of π+, π− and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. For π0 and K− production the amplitude of this Fourier component is consistent with zero.
The spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich in spring 1998. An initial scientific goal is to study K
+-production in pA collisions at ...subthreshold energies far below the free NN-threshold at
T
p=1.58
GeV. This requires the identification of K
+-mesons in a background of pions and protons, about 10
6 times more intense. In this paper the sophisticated detection system and the software procedures for kaon identification are described. With the help of TOF, energy-loss and range measurements as well as the track information from wire chambers, it is possible to measure
d
2σ/
dΩ
dp
for deep subthreshold K
+ production at beam energies down to
T
p=1.0
GeV.
The momentum and helicity density distributions of the strange quark sea in the nucleon are obtained in leading order from charged-kaon production in deep-inelastic scattering on the deuteron. The ...distributions are extracted from spin-averaged K± multiplicities, and from K± and inclusive double-spin asymmetries for scattering of polarized positrons by a polarized deuterium target. The shape of the momentum distribution is softer than that of the average of the u¯ and d¯ quarks. In the region of measurement 0.02<x<0.6 and Q2>1.0 GeV2, the helicity distribution is zero within experimental uncertainties.
A
bstract
Beam-helicity and beam-charge asymmetries in the hard exclusive leptoproduction of real photons from an unpolarised hydrogen target by a 27.6 GeV lepton beam are extracted from the H
ermes
...data set of 2006-2007 using a missing-mass event selection technique. The asymmetry amplitudes extracted from this data set are more precise than those extracted from the earlier data set of 1996-2005 previously analysed in the same manner by H
ermes
. The results from the two data sets are compatible with each other. Results from these combined data sets are extracted and constitute the most precise asymmetry amplitude measurements made in the H
ermes
kinematic region using a missing-mass event selection technique.
New data on
ϕ-meson production in
pp collisions have been obtained at the ANKE facility of COSY-Jülich. These data will provide the energy dependence of the total cross section down to an excess ...energy of 19 MeV above threshold. In combination with the existing SPES-III and COSY-TOF results on
ω-meson production the
ϕ
/
ω
production ratio at this low excess energy will be extracted. As an exciting new aspect an enhancement in the invariant
ϕp mass spectrum is observed at a mass around
1.965
GeV
/
c
2
.
The transverse-target single-spin asymmetry for inclusive deep-inelastic scattering with effectively unpolarized electron and positron beams off a transversely polarized hydrogen target was measured, ...with the goal of searching for a two-photon exchange signal in the kinematic range 0.007<xB<0.9 and 0.25GeV2<Q2<20GeV2. In two separate regions Q2>1GeV2 and Q2<1GeV2, and for both electron and positron beams, the asymmetries are found to be consistent with zero within statistical and systematic uncertainties, which are of order 10−3 for the asymmetries integrated over xB.
PDF
