10,790 research outputs found

    Validity of the Hadronic Freeze-Out Curve

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    We analyze hadro-chemical freeze-out in central Pb+Pb collisions at CERN SPS energies, employing the hybrid version of UrQMD which models hadronization by the Cooper-Frye mechanism, and matches to a final hadron-resonance cascade. We fit the results both before and after the cascade stage using the Statistical Hadronization Model, to assess the effect of the cascade phase. We observe a strong effect on antibaryon yields except anti-{\Omega}, resulting in a shift in T and {\mu}_B. We discuss the implications for the freeze-out curve.Comment: 5 pages, 8 figures. To appear in the proceedings of Quark Matter 2011, the XXII International Conference on Ultrarelativistic Nucleus-Nucleus Collision

    Hadronic Freeze-Out in A+A Collisions meets the Lattice QCD Parton-Hadron Transition Line

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    We analyze hadrochemical freeze-out in central Pb+Pb collisions at CERN SPS and LHC energies. Employing the UrQMD hybrid transport model we study the effects of the final hadron/resonance expansion phase on the hadron multiplicities established at hadronization. The bulk meson yields freeze out directly at hadronization whereas the baryon-antibaryon sector is subject to significant alterations, due to annihilation and regeneration processes. We quantify the latter changes by survival factors for each species which are applied to modify the statistical model predictions for the data. The modified SM analysis recovers the hadronization points, which coincide with the recent lattice QCD predictions of the parton-hadron transition line at finite baryochemical potential.Comment: Proceedings of the 8th International Workshop on Critical Point and Onset of Deconfinement, March 11 to 15, 2013 Napa, California, US

    Economies of Size for Conventional Tillage and No-till Wheat Production

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    Production costs and economies of size for both conventional tillage and no-till wheat production were determined. The reduction in the price of glyphosate after the patent expired improved the relative economics of no-till for continuous monoculture winter wheat. Production costs differ across farm size and by production system.Crop Production/Industries,

    From soft harmonic phonons to fast relaxational dynamics in CH3_{3}NH3_{3}PbBr3_{3}

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    The lead-halide perovskites, including CH3_{3}NH3_{3}PbBr3_{3}, are components in cost effective, highly efficient photovoltaics, where the interactions of the molecular cations with the inorganic framework are suggested to influence the electronic and ferroelectric properties. CH3_{3}NH3_{3}PbBr3_{3} undergoes a series of structural transitions associated with orientational order of the CH3_{3}NH3_{3} (MA) molecular cation and tilting of the PbBr3_{3} host framework. We apply high-resolution neutron scattering to study the soft harmonic phonons associated with these transitions, and find a strong coupling between the PbBr3_{3} framework and the quasistatic CH3_{3}NH3_{3} dynamics at low energy transfers. At higher energy transfers, we observe a PbBr6_{6} octahedra soft mode driving a transition at 150 K from bound molecular excitations at low temperatures to relatively fast relaxational excitations that extend up to \sim 50-100 meV. We suggest that these temporally overdamped dynamics enables possible indirect band gap processes in these materials that are related to the enhanced photovoltaic properties.Comment: (main text - 5 pages, 4 figures; supplementary information - 3 pages, 3 figures

    Magnetic field splitting of the spin-resonance in CeCoIn5

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    Neutron scattering in strong magnetic fields is used to show the spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T, near the critical field for the incommensurate "Q-phase" indicating that the Q-phase is a bose condensate of spin excitons.Comment: 5 pages, 4 figure
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