4,642 research outputs found

    Stability and instability of a hot and dilute nuclear droplet

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    The diabatic approach to collective nuclear motion is reformulated in the local-density approximation in order to treat the normal modes of a spherical nuclear droplet analytically. In a first application the adiabatic isoscalar modes are studied and results for the eigenvalues of compressional (bulk) and pure surface modes are presented as function of density and temperature inside the droplet, as well as for different mass numbers and for soft and stiff equations of state. We find that the region of bulk instabilities (spinodal regime) is substantially smaller for nuclear droplets than for infinite nuclear matter. For small densities below 30% of normal nuclear matter density and for temperatures below 5 MeV all relevant bulk modes become unstable with the same growth rates. The surface modes have a larger spinodal region, reaching out to densities and temperatures way beyond the spinodal line for bulk instabilities. Essential experimental features of multifragmentation, like fragmentation temperatures and fragment-mass distributions (in particular the power-law behavior) are consistent with the instability properties of an expanding nuclear droplet, and hence with a dynamical fragmentation process within the spinodal regime of bulk and surface modes (spinodal decomposition).Comment: 17 pages, 11 figures, LaTeX2e, EPJA style (included

    Instabilities of a hot expanded nuclear droplet

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    The stability of hot expanded nuclear droplets against small bulk and surface oscillations is examined and possible consequences for multifragmentation are discussed.Comment: LaTeX (uses epsfig.sty), 6 pages with 6 eps figures inside text. Talk given at XXVII International Workshop on Gross Properties of Nuclei and Nuclear Excitations, "MULTIFRAGMENTATION", Hirschegg, January 17--23, 199

    Instabilities in Nuclei

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    The evolution of dynamical perturbations is examined in nuclear multifragmentation in the frame of Vlasov equation. Both plane wave and bubble type of perturbations are investigated in the presence of surface (Yukawa) forces. An energy condition is given for the allowed type of instabilities and the time scale of the exponential growth of the instabilities is calculated. The results are compared to the mechanical spinodal region predictions. PACS: 25.70 MnComment: 22 pages, latex, with 5 PS figures, available at http://www.gsi.de/~papp

    Jets and produced particles in pp collisions from SPS to RHIC energies for nuclear applications

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    Higher-order pQCD corrections play an important role in the reproduction of data at high transverse momenta in the energy range 20 GeV ≤s≤200 \leq \sqrt{s} \leq 200 GeV. Recent calculations of photon and pion production in pppp collisions yield detailed information on the next-to-leading order contributions. However, the application of these results in proton-nucleus and nucleus-nucleus collisions is not straightforward. The study of nuclear effects requires a simplified understanding of the output of these computations. Here we summarize our analysis of recent calculations, aimed at handling the NLO results by introducing process and energy-dependent KK factors.Comment: 4 pages with 5 eps figures include

    K+/pi+ probes of jet quenching in AA collisions

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    Non-abelian energy loss in quark gluon plasma is shown to lead to novel hadron ratio suppression patterns in ultrarelativistic nuclear collisions. We apply recent (GLV) estimates for the gluon radiative energy loss, which increases linearly with the jet energy up to E<20 GeV and depends quadratically on the nuclear radius, R. The K+/\pi+ ratio is found to be most sensitive to the initial density of the plasma.Comment: Presented at 6th International Conference on Strange Quarks in Matter: 2001: A Flavourspace Odyssey (SQM2001), Frankfurt, Germany, 25-29 Sep 200

    Kaon and Pion Ratio Probes of Jet Quenching in Nuclear Collisions

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    Non-abelian energy loss in quark gluon plasmas is shown to lead to novel hadron ratio suppression patterns in ultrarelativistic nuclear collisions. We apply GLV estimates for the gluon radiative energy loss. The K^-/K^+ and K^+/\pi^+ ratios are found to be most sensitive to the initial density of the plasma.Comment: 10 pages in Latex, 6 EPS figure

    Pion production in d+Au collisions at RHIC energy

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    We present our results on neutral pion pi0 production in pp and dAu collisions at RHIC energy. Pion spectra are calculated in a next-to-leading order (NLO) perturbative QCD-based model. The model includes the transverse component of the initial parton distribution (``intrinsic kT''). We compare our results to the available experimental data from RHIC, and fit the data with high precision. The calculation tuned this way is repeated for the dAu collision, and used to investigate the interplay of shadowing and multiple scattering at RHIC. The centrality dependence of the nuclear modification factor shows a measurable difference between different shadowing parameterizations.Comment: Final version published in the Eur. Phys. J. ST in the Proceedings of the Zimanyi Memorial Workshop, 2-4 July, 2007, Budapest, Hungary; 12 pages in Latex, 6 EPS figure
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