[en] The PHOBOS Collaboration has measured transverse momentum distributions of charged hadrons produced in Cu+Cu collisions at √sNN = 200 and 62.4 GeV. The nuclear modification factor RAANpart is calculated relative to p+p data at both collision energies as a function of collision centrality. For the same number of participating nucleons, RAANpart is essentially the same in both systems over the full range of pT that is measured. In addition, we observe that within experimental uncertainties, the ratio of 200 GeV to 62.4 GeV Cu+Cu yields has only a moderate centrality dependence and is consistent with the value previously measured in Au+Au collisions for a broad range of pT. (author)

[en] We compare, from a crystallographic point of view, the data quality obtained using laboratory x-ray diffractometers equipped with a Molybdenum micro-source using different detector types: CCD, CMOS and XPAD hybrid pixel. First we give an overview of the working principle of these different detector types with a focus on their principal differences and their impact on the data quality. Then, using the example of an organic crystal, a comparison between the detector systems concerning the raw data statistics, the refinement agreement factors, the deformation electron density maps, and the residual density after multipolar refinement is presented. It is found that the data quality obtained with the XPAD detector is the best, even though the detection efficiency at the Mo energy (17.5 keV) is only 37% due to the Si-sensor layer thickness of 300 μ m. Finally, we discuss the latest x-ray detector developments with an emphasis on the sensor material, where replacing Si by another material such as GaAs would yield detection efficiencies close to 100%, up to energies of 40 keV for hybrid pixel detectors. (invited comment)

[en] The rare case of glutaric aciduria typ I (GA Type I) is described. Its characteristics are discussed and compared with cases in the literature. This disease is basically due to a lack of glutaryl-CoA-dehydrogenase with increased excretion of glutaric acid. Most authors describe frontotemporal cerebral atrophy. In the majority of cases macrocephaly is also present. This sign was also seen in our case and was the reason for performing an ultrasound examination, CT and MR. Ultrasound and CT showed a large insular cistern with incomplete formation of the opercula and frontal atrophy. In addition MR revealed hyperintensity of the basal ganglia and the periventricular white matter. To our knowledge this is the first publication of radiological findings in GA Type I in the German language. (orig.)

[en] A measurement of two-particle correlations with a high transverse momentum trigger particle (p_T^trig>2.5 GeV/c) is presented for Au+Au collisions at √(s_NN)=200 GeV over the uniquely broad longitudinal acceptance of the PHOBOS detector (-4<Δη<2). A broadening of the away-side azimuthal correlation compared to elementary collisions is observed at all Δη. As in p+p collisions, the near side is characterized by a peak of correlated partners at small angle relative to the trigger particle. However, in central Au+Au collisions an additional correlation extended in Δη and known as the 'ridge' is found to reach at least |Δη|≅4. The ridge yield is largely independent of Δη over the measured range, and it decreases towards more peripheral collisions. For the chosen p_T^trig cut, the ridge yield is consistent with zero for events with less than roughly 100 participating nucleons.

[en] We present transverse momentum distributions of charged hadrons produced in Cu+Cu collisions at √(s_NN)=62.4 and 200 GeV. The spectra are measured for transverse momenta of 0.25< p_T<5.0 GeV/c at √(s_NN)=62.4 GeV and 0.25< p_T<7.0 GeV/c at √(s_NN)=200 GeV, in a pseudorapidity range of 0.2<η<1.4. The nuclear modification factor R_AA is calculated relative to p+p data at both collision energies as a function of collision centrality. At a given collision energy and fractional cross section, R_AA is observed to be systematically larger in Cu+Cu collisions compared to Au+Au. However, for the same number of participating nucleons, R_AA is essentially the same in both systems over the measured range of p_T, in spite of the significantly different geometries of the Cu+Cu and Au+Au systems

[en] This article presents results on event-by-event elliptic flow fluctuations in Au+Au collisions at √(s_NN)= 200 GeV, where the contribution from non-flow correlations has been subtracted. An analysis method is introduced to measure non-flow correlations, relying on the assumption that non-flow correlations are most prominent at short ranges (|Δη|<2). Assuming that non-flow correlations are of the order that is observed in p+p collisions for long-range correlations (|Δη|>2), relative elliptic flow fluctuations of approximately 30-40% are observed. These results are consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. It is found that the long-range non-flow correlations in Au+Au collisions would have to be more than an order of magnitude strongercompared to the p+p data to lead to the observed azimuthal anisotropy fluctuations with no intrinsic elliptic flow fluctuations.

[en] This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system

[en] This Letter presents the first measurement of event-by-event fluctuations of the elliptic flow parameter v₂ in Au+Au collisions at √(s_NN)=200 GeV as a function of collision centrality. The relative nonstatistical fluctuations of the v₂ parameter are found to be approximately 40%. The results, including contributions from event-by-event elliptic flow fluctuations and from azimuthal correlations that are unrelated to the reaction plane (nonflow correlations), establish an upper limit on the magnitude of underlying elliptic flow fluctuations. This limit is consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. These results provide important constraints on models of the initial state and hydrodynamic evolution of relativistic heavy ion collisions.

[en] Antiparticle to particle ratios for identified protons, kaons, and pions at √(s_NN)=62.4 and 200 GeV in Cu+Cu collisions are presented as a function of centrality for the midrapidity region of 0.2<η<1.4. No strong dependence on centrality is observed. For the < p>/< p> ratio at < p_T>≅0.51 GeV/c, we observe an average value of 0.50±0.003_(stat)±0.04_(syst) and 0.77±0.008_(stat)±0.05_(syst) for the 10% most central collisions of 62.4 and 200 GeV Cu+Cu, respectively. The values for all three particle species measured at √(s_NN)=200 GeV are in agreement within systematic uncertainties with that seen in both heavier and lighter systems measured at the same RHIC energy. This indicates that system size does not appear to play a strong role in determining the midrapidity chemical freeze-out properties affecting the antiparticle to particle ratios of the three most abundant particle species produced in these collisions

[en] We present results on two-particle angular correlations in proton-proton collisions at center-of-mass energies of 200 and 410 GeV. The PHOBOS experiment at the BNL Relativistic Heavy Ion Collider has a uniquely large coverage for charged particles, giving the opportunity to explore the correlations at both short- and long-range scales. At both energies, a complex two-dimensional correlation structure in Δη and Δφ is observed. In the context of an independent cluster model of short-range correlations, the cluster size and its decay width are extracted from the two-particle pseudorapidity correlation function and compared with previous measurements in proton-proton and proton-antiproton collisions, as well as PYTHIA and HIJING predictions