138,083 research outputs found

    Azimuthal asymmetry in transverse energy flow in nuclear collisions at high energies

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    The azimuthal pattern of transverse energy flow in nuclear collisions at RHIC and LHC energies is considered. We show that the probability distribution of the event-by-event azimuthal disbalance in transverse energy flow is essentially sensitive to the presence of the semihard minijet component.Comment: 6 pages, 2 figure

    Strangeness Production in Chemically Non-Equilibrated Parton Plasma

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    Strangeness production was investigated during the equilibration of a gluon dominated parton plasma produced at RHIC and LHC energies. The time evolution of parton densities are followed by a set of rate equations in a 1-dimensional expanding system. The strangeness production will depend on the initial chemical equilibration level and in our case the parton densities will remain far from the full equilibrium. We investigate the influence of gluon fragmentation on final strangeness content.Comment: 12 pages (LaTeX) + 2 postscript figures (tarred, compressed, uuencoded) included. Review to appear in Proceedings of Strangeness'95, Tucson, Arizona, Jan. 4--6 1995. (American Institute of Physics

    Where is the jet quenching in Pb+Pb collisions at 158 AGeV?

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    Because of the rapidly falling particle spectrum at large pTp_T from jet fragmentation at the CERN SPS energy, the high-pTp_T hadron distribution should be highly sensitive to parton energy loss inside a dense medium as predicted by recent perturbative QCD (pQCD) studies. A careful analysis of recent data from CERN SPS experiments via pQCD calculation shows little evidence of energy loss. This implies that either the life-time of the dense partonic matter is very short or one has to re-think about the problem of parton energy loss in dense matter. The hadronic matter does not seem to cause jet quenching in Pb+PbPb+Pb collisions at the CERN SPS. High-pTp_T two particle correlation in the azimuthal angle is proposed to further clarify this issue.Comment: 4 pages with 2 ps figures. Minors changes are made in the text with updated references. Revised version to appear in Phys. Rev. Letter

    Finite Volume Analysis of Nonlinear Thermo-mechanical Dynamics of Shape Memory Alloys

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    In this paper, the finite volume method is developed to analyze coupled dynamic problems of nonlinear thermoelasticity. The major focus is given to the description of martensitic phase transformations essential in the modelling of shape memory alloys. Computational experiments are carried out to study the thermo-mechanical wave interactions in a shape memory alloy rod, and a patch. Both mechanically and thermally induced phase transformations, as well as hysteresis effects, in a one-dimensional structure are successfully simulated with the developed methodology. In the two-dimensional case, the main focus is given to square-to-rectangular transformations and examples of martensitic combinations under different mechanical loadings are provided.Comment: Keywords: shape memory alloys, phase transformations, nonlinear thermo-elasticity, finite volume metho

    Numerical Model For Vibration Damping Resulting From the First Order Phase Transformations

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    A numerical model is constructed for modelling macroscale damping effects induced by the first order martensite phase transformations in a shape memory alloy rod. The model is constructed on the basis of the modified Landau-Ginzburg theory that couples nonlinear mechanical and thermal fields. The free energy function for the model is constructed as a double well function at low temperature, such that the external energy can be absorbed during the phase transformation and converted into thermal form. The Chebyshev spectral methods are employed together with backward differentiation for the numerical analysis of the problem. Computational experiments performed for different vibration energies demonstrate the importance of taking into account damping effects induced by phase transformations.Comment: Keywords: martensite transformation, thermo-mechanical coupling, vibration damping, Ginzburg-Landau theor

    Studying minijets via the pTp_T dependence of two-particle correlation in azimuthal angle ϕ\phi

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    Following my previous proposal that two-particle correlation functions can be used to resolve the minijet contribution to particle production in minimum biased events of high energy hadronic interactions, I study the pTp_T and energy dependence of the correlation. Using HIJING Monte Carlo model, it is found that the correlation c(ϕ1,ϕ2)c(\phi_1,\phi_2) in azimuthal angle ϕ\phi between two particles with pT>pTcutp_T>p_T^{cut} resembles much like two back-to-back jets as pTcutp_T^{cut} increases at high colliding energies due to minijet production. It is shown that c(0,0)c(0,π)c(0,0)-c(0,\pi), which is related to the relative fraction of particles from minijets, increases with energy. The background of the correlation for fixed pTcutp_T^{cut} also grows with energy due to the increase of multiple minijet production. Application of this analysis to the study of jet quenching in ultrarelativistic heavy ion collisions is also discussed.Comment: 11 pages Latex text and 8 ps figures, LBL-3349