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Register a new userDetermination of Deuteron Beam Polarizations at COSY
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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 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 a number of secondary standards that can be used in subsequent experiments at the facility.
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The luminosity for a WASA-at-COSY experiment involving the pd reaction at 2.14 GeV proton-beam energy is determined by the forward pd elastic scattering, which yields an average beam-on-target value of [5.2pm0.3(stat)pm0.3(syst)]*10^{30} s^{-1}cm^{-2}. In addition, the forward pd elastic-scattering angular distribution is obtained with four-momentum transfer squared -t between 0.16 (GeV/c)^{2} and 0.78 (GeV/c)^{2} at this beam energy, which is compared with other experimental data and the pd double scattering model.
The results of the measurements of the vector polarization of the extracted deuteron beam at Nuclotron are presented. The intensity of the polarized deuteron beam during the measurements was 2.5*10^7 particles/spill. The measurements were made at the initial deuteron momenta of 5 and 3.5 GeV/c. The averaged polarizations of the beam were 0.606 +/- 0.014 and 0.540+/- 0.019, respectively.
We report on the COSY-11 measurements of the analysing power for the p(pol)p --> ppeta reaction and interpret the results in the framework of the meson exchange models.
The beam-spin asymmetry, $Sigma$, for the reaction $gamma drightarrow pn$ has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (JLab) for six photon-energy bins between 1.1 and 2.3 GeV, and proton angles in the center-of-mass frame, $theta_{c.m.}$, between $25^circ$ and $160^circ$. These are the first measurements of beam-spin asymmetries at $theta_{c.m.}=90^circ$ for photon-beam energies above 1.6 GeV, and the first measurements for angles other than $theta_{c.m.}=90^circ$. The angular and energy dependence of $Sigma$ is expected to aid in the development of QCD-based models to understand the mechanisms of deuteron photodisintegration in the transition region between hadronic and partonic degrees of freedom, where both effective field theories and perturbative QCD cannot make reliable predictions.
We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $sqrt{s_text{NN}} = $7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at RHIC. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter $B_2$ are discussed. We find that the values of $B_2$ for anti-deuterons are systematically lower than those for deuterons, indicating that the correlation volume of anti-baryons is larger than that of baryons at $sqrt{s_text{NN}}$ from 19.6 to 39 GeV. In addition, values of $B_2$ are found to vary with collision energy and show a broad minimum around $sqrt{s_text{NN}}= $20 to 40 GeV, which might imply a change of the equation of state of the medium in these collisions.
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