462 research outputs found

    Geochemical indices allow estimation of heavy metal background concentration in soils

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    Defining background concentrations for heavy metals in soils is essential for recognizing and managing soil pollution. However, background concentrations of metals in soils can vary naturally by several orders of magnitude. Moreover, many soils have also been subject to unquantifiable anthropogenic inputs of metals, in some cases, for centuries. Hence determination of heavy metal background concentrations in soils has to date been fraught with difficulty. Here we demonstrate that there are associations between the background heavy metal and Fe or Mn contents in soils which appear to be consistent for seven important heavy metals of environmental concern. The relationships are remarkably independent of both soil type and climatic setting. These observations provide the basis for a series of general equations from which it is proposed Southeast Asian including Australian, and possibly worldwide background concentrations for As, Cr, Co, Cu, Ni, Pb, and Zn in soils can be derived.R. E. Hamon, M. J. McLaughlin, R. J. Gilkes, A. W. Rate, B. Zarcinas, A. Robertson, G. Cozens, N. Radford and L. Bettena

    Laying the groundwork at the AGS: Recent results from experiment E895

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    The E895 Collaboration at the Brookhaven AGS has performed a systematic investigation of Au+Au collisions at 2-8 AGeV, using a large-acceptance Time Projection Chamber. In addition to extensive measurements of particle flow, spectra, two-particle interferometry, and strangeness production, we have performed novel hybrid analyses, including azimuthally-sensitive pion HBT, extraction of the six-dimensional pion phasespace density, and a first measurement of the Lambda-proton correlation function.Comment: Presented at Quark Matter 2001, 8 pages, 5 figure

    Antiproton Production in p+Ap+A Collisions at AGS Energies

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    Inclusive and semi-inclusive measurements are presented for antiproton (pˉ\bar{p}) production in proton-nucleus collisions at the AGS. The inclusive yields per event increase strongly with increasing beam energy and decrease slightly with increasing target mass. The pˉ\bar{p} yield in 17.5 GeV/c p+Au collisions decreases with grey track multiplicity, NgN_g, for Ng>0N_g>0, consistent with annihilation within the target nucleus. The relationship between NgN_g and the number of scatterings of the proton in the nucleus is used to estimate the pˉ\bar{p} annihilation cross section in the nuclear medium. The resulting cross section is at least a factor of five smaller than the free pˉ−p\bar{p}-p annihilation cross section when assuming a small or negligible formation time. Only with a long formation time can the data be described with the free pˉ−p\bar{p}-p annihilation cross section.Comment: 8 pages, 6 figure

    Longitudinal Flow of Protons from 2-8 AGeV Central Au+Au Collisions

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    Rapidity distributions of protons from central 197^{197}Au + 197^{197}Au collisions measured by the E895 Collaboration in the energy range from 2 to 8 AGeV at the Brookhaven AGS are presented. Longitudinal flow parameters derived using a thermal model including collective longitudinal expansion are extracted from these distributions. The results show an approximately linear increase in the longitudinal flow velocity, L_{L}, as a function of the logarithm of beam energy.Comment: 5 Pages, including 3 figures, 1 tabl

    Near-threshold production of the multi-strange Ξ−\Xi^- hyperon

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    The yield for the multi-strange Ξ−\Xi^{-} hyperon has been measured in 6 AGeV Au+Au collisions via reconstruction of its decay products π−\pi^{-} and Λ\Lambda, the latter also being reconstructed from its daughter tracks of π−\pi^{-} and p. The measurement is rather close to the threshold for Ξ−\Xi^{-} production and therefore provides an important test of model predictions. The measured yield for Ξ−\Xi^{-} and Λ\Lambda are compared for several centralities. In central collisions the Ξ−\Xi^{-} yield is found to be in excellent agreement with statistical and transport model predictions, suggesting that multi-strange hadron production approaches chemical equilibrium in high baryon density nuclear matter.Comment: Submitted to PR

    Charged Pion Production in 2 to 8 AGeV Central Au+Au Collisions

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    Momentum spectra of charged pions over nearly full rapidity coverage from target to beam rapidity have been measured in the 0-5% most central Au+Au collisions in the beam energy range from 2 to 8 AGeV by the E895 Experiment. Using a thermal parameterization to fit the transverse mass spectra, rapidity density distributions are extracted. The observed spectra are compared with predictions from the RQMD v2.3 cascade model and also to a thermal model including longitudinal flow. The total 4Ï€\pi yields of the charged pions are used to infer an initial state entropy produced in the collisions.Comment: 13 pgs, 19 figs, accepted by Phys. Rev. C. Data tables available at http://nuclear.ucdavis.edu/~e895/published_spectra.htm
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