1,056 research outputs found

    Carbon and oxygen isotopic composition of the Middle Miocene Badenian gypsum-associated limestones of West Ukraine

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    The middle Miocene Badenian basin of the Carpathian Foredeep is characterized by complex sedimentary and diagenetic carbonate-evaporite transitions. Six locations have been selected to evaluate the controls on the carbon and oxygen isotopic composition of the Badenian gypsum-associated limestones of the Tyras Formation in West Ukraine. At three locations marine limestones overlie the gypsum, at one location (Anadoly) the gypsum-associated limestones are polygenic, and at two localities (Pyshchatyntsi and Lozyna) gypsum deposits are lacking. The studied limestones have originated as primary, mostly peloidal carbonates as well as secondary carbonates formed by hypogene sulphate calcitisation. They show a wide range of d13C (from from -0.9‰ to -39.8‰) and d18O values (from 0.9‰ to -12.2‰). The Badenian limestones formed in marine environments (either as deposits accumulated at the bottom of the sea or forming the infillings of solution cavities within gypsum) have less negative d18O values compared to predominantly diagenetic formations. Wide ranges and usually very negative d13C values and low d18O values of those limestones indicate that they suffered important meteoric diagenesis as supported by common sparitic fabrics. In addition, a large range of d13C values even in the group of samples characterized by less-negative d18O values shows that bacterial sulphate reduction and methane oxidation were active processes in the pore fluids of the Tyras Formation. Very low carbon isotopic compositions (d13C values from -22 to -40‰) of some sparitic limestones in the studied sections indicate the occurrence of oxidized methane within the diagenetic environment. Accordingly, the isotopic signatures of the studied limestones are a combination of both primary and secondary processes, the latter having a primordial importance. The common occurrence of similar negative d13C and d18O values in evaporite-related carbonates in other Miocene evaporite basins suggest that extensive dissolution- reprecipitation in diagenetic or vadose-phreatic environments were common in evaporite-related carbonates

    The STAR Silicon Strip Detector (SSD)

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    The STAR Silicon Strip Detector (SSD) completes the three layers of the Silicon Vertex Tracker (SVT) to make an inner tracking system located inside the Time Projection Chamber (TPC). This additional fourth layer provides two dimensional hit position and energy loss measurements for charged particles, improving the extrapolation of TPC tracks through SVT hits. To match the high multiplicity of central Au+Au collisions at RHIC the double sided silicon strip technology was chosen which makes the SSD a half million channels detector. Dedicated electronics have been designed for both readout and control. Also a novel technique of bonding, the Tape Automated Bonding (TAB), was used to fullfill the large number of bounds to be done. All aspects of the SSD are shortly described here and test performances of produced detection modules as well as simulated results on hit reconstruction are given.Comment: 11 pages, 8 figures, 1 tabl

    CERN Proton Synchrotron Complex High-Level Controls Renovation

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    After a detailed study of the Proton Synchrotron (PS) complex requirements by experts of CERN controls & operation groups, a proposal to develop a new system, called Injector Controls Architecture (InCA), was presented to and accepted by the management late 2007. Aiming at the homogenisation of the control systems across CERN accelerators, InCA is based on components developed for the Large Hadron Collider (LHC) but also new components required to fulfil operation needs. In 2008, the project was in its elaboration phase and we successfully validated its architecture and critical use-cases during several machine development sessions. After description of the architecture put in place and the components used, this paper describes the planning approach taken combining iterative development phases with deployment in operation for validation sessions

    Phase-space dependence of particle-ratio fluctuations in Pb+Pb collisions from 20A to 158A GeV beam energy

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    A novel approach, the identity method, was used for particle identification and the study of fluctuations of particle yield ratios in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS). This procedure allows to unfold the moments of the unknown multiplicity distributions of protons (p), kaons (K), pions (π\pi) and electrons (e). Using these moments the excitation function of the fluctuation measure νdyn\nu_{\text{\text{dyn}}}[A,B] was measured, with A and B denoting different particle types. The obtained energy dependence of νdyn\nu_{\text{dyn}} agrees with previously published NA49 results on the related measure σdyn\sigma_{\text{dyn}}. Moreover, νdyn\nu_{\text{dyn}} was found to depend on the phase space coverage for [K,p] and [K,π\pi] pairs. This feature most likely explains the reported differences between measurements of NA49 and those of STAR in central Au+Au collisions

    Centrality dependence of proton and antiproton spectra in Pb+Pb collisions at 40A GeV and 158A GeV measured at the CERN SPS

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    The yields of (anti-)protons were measured by the NA49 Collaboration in centrality selected Pb+Pb collisions at 40A GeV and 158A GeV. Particle identification was obtained in the laboratory momentum range from 5 to 63 GeV/c by the measurement of the energy loss dE/dx in the TPC detector gas. The corresponding rapidity coverage extends 1.6 units from mid-rapidity into the forward hemisphere. Transverse mass spectra, the rapidity dependences of the average transverse mass, and rapidity density distributions were studied as a function of collision centrality. The values of the average transverse mass as well as the midrapidity yields of protons when normalized to the number of wounded nucleons show only modest centrality dependences. In contrast, the shape of the rapidity distribution changes significantly with collision centrality, especially at 40A GeV. The experimental results are compared to calculations of the HSD and UrQMD transport models.Comment: 25 pages, 12 figures, submitted to PR

    Energy dependence of kaon-to-proton ratio fluctuations in central Pb+Pb collisions from sNN\sqrt{s_{NN}} = 6.3 to 17.3 GeV

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    Kaons and protons carry large parts of two conserved quantities, strangeness and baryon number. It is argued that their correlation and thus also fluctuations are sensitive to conditions prevailing at the anticipated parton-hadron phase boundary. Fluctuations of the (K++K)/(p+pˉ)(\mathrm{K}^+ + \mathrm{K}^-)/(\mathrm{p}+\bar{\mathrm{p}}) and K+/p\mathrm{K}^+/\mathrm{p} ratios have been measured for the first time by NA49 in central Pb+Pb collisions at 5 SPS energies between sNN\sqrt{s_{NN}}= 6.3 GeV and 17.3 GeV. Both ratios exhibit a change of sign in σdyn\sigma_{\mathrm{dyn}}, a measure of non-statistical fluctuations, around sNN\sqrt{s_{NN}} = 8 GeV. Below this energy, σdyn\sigma_{\mathrm{dyn}} is positive, indicating higher fluctuation compared to a mixed event background sample, while for higher energies, σdyn\sigma_{\mathrm{dyn}} is negative, indicating correlated emission of kaons and protons. The results are compared to UrQMD calculations which which give a good description at the higher SPS energies, but fail to reproduce the transition to positive values.Comment: 5 pages, 4 figure

    Antideuteron and deuteron production in mid-central Pb+Pb collisions at 158AA GeV

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    Production of deuterons and antideuterons was studied by the NA49 experiment in the 23.5% most central Pb+Pb collisions at the top SPS energy of sNN\sqrt{s_{NN}}=17.3 GeV. Invariant yields for dˉ\bar{d} and dd were measured as a function of centrality in the center-of-mass rapidity range 1.2<y<0.6-1.2<y<-0.6. Results for dˉ(d)\bar{d}(d) together with previously published pˉ(p)\bar{p}(p) measurements are discussed in the context of the coalescence model. The coalescence parameters B2B_2 were deduced as a function of transverse momentum ptp_t and collision centrality.Comment: 9 figure

    Proton -- Lambda Correlations in Central Pb+Pb Collisions at sqrt(s_{NN}) = 17.3 GeV

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    The momentum correlation between protons and lambda particles emitted from central Pb+Pb collisions at sqrt(s_{NN}) = 17.3 GeV was studied by the NA49 experiment at the CERN SPS. A clear enhancement is observed for small relative momenta (q_{inv} < 0.2 GeV). By fitting a theoretical model, which uses the strong interaction between the proton and the lambda in a given pair, to the measured data a value for the effective source size is deduced. Assuming a static Gaussian source distribution we derive an effective radius parameter of R_G = 3.02 \pm 0.20$(stat.)^{+0.44}_{-0.16}(syst.) fm.Comment: 14 pages, 9 figures, submitted to Phys. Rev.

    System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy

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    Measurements of charged pion and kaon production are presented in centrality selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in semi-central C+C and Si+Si interactions at 40A GeV. Transverse mass spectra, rapidity spectra and total yields are determined as a function of centrality. The system-size and centrality dependence of relative strangeness production in nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from the data presented here and published data for C+C and Si+Si collisions at 158A GeV beam energy. At both energies a steep increase with centrality is observed for small systems followed by a weak rise or even saturation for higher centralities. This behavior is compared to calculations using transport models (UrQMD and HSD), a percolation model and the core-corona approach.Comment: 32 pages, 14 figures, 4 tables, typo table II correcte
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