We present measurements of elliptic flow (\(v_2\)) of electrons from the decays of heavy-flavor hadrons (\(e_{HF}\)) by the STAR experiment. For Au+Au collisions at \(\sqrt{s_{\rm NN}} = \) 200 GeV ...we report \(v_2\), for transverse momentum (\(p_T\)) between 0.2 and 7 GeV/c using three methods: the event plane method (\(v_{2}\){EP}), two-particle correlations (\(v_2\){2}), and four-particle correlations (\(v_2\){4}). For Au+Au collisions at \(\sqrt{s_{\rm NN}}\) = 62.4 and 39 GeV we report \(v_2\){2} for \(p_T< 2\) GeV/c. \(v_2\){2} and \(v_2\){4} are non-zero at low and intermediate \(p_T\) at 200 GeV, and \(v_2\){2} is consistent with zero at low \(p_T\) at other energies. The \(v_2\){2} at the two lower beam energies is systematically lower than at \(\sqrt{s_{\rm NN}} = \) 200 GeV for \(p_T < 1\) GeV/c. This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to \(\sqrt{s_{\rm NN}} = 200\) GeV.
We present measurements of the near-side of triggered di-hadron correlations using neutral strange baryons (\(\Lambda\), \(\bar{\Lambda}\)) and mesons (\(K^0_S\)) at intermediate transverse momentum ...(3 \(<\) \(p_T\) \(<\) 6 GeV/\(c\)) to look for possible flavor and baryon/meson dependence. This study is performed in \(d\)+Au, Cu+Cu and Au+Au collisions at \(\sqrt{s_{{NN}}}\) = 200 GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations due to jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.
We report on the measurement of \(\rm{J}/\psi\) production in the dielectron channel at mid-rapidity (|y|<1) in p+p and d+Au collisions at \(\sqrt{s_{NN}}\) = 200 GeV from the STAR experiment at the ...Relativistic Heavy Ion Collider. The transverse momentum \(p_{T}\) spectra in p+p for \(p_{T}\) < 4 GeV/c and d+Au collisions for \(p_{T}\) < 3 GeV/c are presented. These measurements extend the STAR coverage for \(\rm{J}/\psi\) production in p+p collisions to low \(p_{T}\). The \(<p_{T}^{2}>\) from the measured \(\rm{J}/\psi\) invariant cross section in p+p and d+Au collisions are evaluated and compared to similar measurements at other collision energies. The nuclear modification factor for \(\rm{J}/\psi\) is extracted as a function of \(p_{T}\) and collision centrality in d+Au and compared to model calculations using the modified nuclear Parton Distribution Function and a final-state \(\rm{J}/\psi\) nuclear absorption cross section.
We report the first di-jet transverse momentum asymmetry measurements from Au+Au and p+p collisions at RHIC. The two highest-energy back-to-back jets reconstructed from fragments with transverse ...momenta above 2 GeV/c display a significantly stronger momentum imbalance in heavy-ion collisions than in the p+p reference. When re-examined with correlated soft particles included, we observe that these di-jets then exhibit a unique new feature -- momentum balance is restored to that observed in p+p for a jet resolution parameter of R=0.4, while re-balancing is not attained with a smaller value of R=0.2.
The inclusive \(J/\psi\) transverse momentum (\(p_{T}\)) spectra and nuclear modification factors are reported at midrapidity (\(|y|<1.0\)) in Au+Au collisions at \(\sqrt{s_{NN}}=\) 39, 62.4 and 200 ...GeV taken by the STAR experiment. A suppression of \(J/\psi\) production, with respect to {\color{black}the production in \(p+p\) scaled by the number of binary nucleon-nucleon collisions}, is observed in central Au+Au collisions at these three energies. No significant energy dependence of nuclear modification factors is found within uncertainties. The measured nuclear modification factors can be described by model calculations that take into account both suppression of direct \(J/\psi\) production due to the color screening effect and \(J/\psi\) regeneration from recombination of uncorrelated charm-anticharm quark pairs.
The synthesis of a photo-sensitive analogue of pork insulin (A1-N gamma-(4-azidophenylacetyl)-D-alpha, gamma-diaminobutyric acidinsulin is reported. It could be shown that this analogue forms ...specific cross-links to binding proteins on irradiation with UV light. Furthermore, it was shown that the photo-label itself was not iodinated, nor did it influence the normal distribution of iodination. It can be concluded that this derivative bears all of the characteristics necessary for specifically labeling membrane-bound receptors.
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