7,619 research outputs found

    Duality and Chiral Restoration from Dilepton Production in Relativistic Heavy-Ion Collisions

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    We discuss the recent status in the theoretical understanding of dilepton production in central heavy-ion reactions with the Pb-beam at the full CERN-SpS energy of 158 AGeV. In the low-mass region (MM\le~1 GeV) a strong broadening of the vector meson resonances in hot and dense matter (especially for the ρ\rho meson) entails thermal dilepton rates very reminiscent to perturbative qqˉq\bar q annihilation close to the expected phase boundary of the chiral symmetry restoring transition. A consistent description of the experimentally observed enhancement at both low and intermediate masses (1.5 GeV~M\le M \le~3 GeV) in terms of thermal radiation from an expanding fireball can be obtained.Comment: Talk given at ISMD '99 on 'QCD & Multiparticle Production' (Brown University, Providence, Aug. 9-13), 7 pages LaTeX including 6 ps-/eps-figures and sprocl.st

    Pi+ Pi- Emission in High-Energy Nuclear Collisions

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    Realistic vacuum ππ\pi\pi interactions are employed to investigate thermal π+π\pi^+\pi^- emission spectra from the late stages of heavy-ion reactions at ultrarelativistic energies. Hadronic in-medium effects, including many-body ρ\rho-meson spectral functions used earlier to describe the dilepton excess observed at CERN-SPS energies, are implemented to assess resulting modifications in relation to recent measurements of π+π\pi^+\pi^- invariant-mass spectra by the STAR collaboration in pp-pp and AuAu-AuAu collisions at sNN\sqrt{s_{NN}}=200 GeV. Statistical model estimates for the ρ0/π\rho^0/\pi^- and K/KK^*/K ratios close to the expected thermal freezeout are also given.Comment: 9 pages RevTeX including 5 eps-figures, summary slightly expanded and 5 references adde

    Probabilistic dynamics of a global horizontal sounding system

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    Probability method for position and motion of large numbers of constant-level balloons - atmospheric circulatio

    Metastasis as a faulty recapitulation of ontogeny

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    RAF oncogenes are involved in a variety of phenotypic switch phenomena. If for example oncogenic RAF is expressed together with Myc in B lineage cells, a lineage switch to macrophages occurs at low frequency in vitro and in vivo. In addition, if RAF is expressed in type II alveolar epithelial cells slow growing lung adenomas are formed and a switch from columnar to cuboidal cells is detected in these mice upon p53 deletion. A similar switch is also seen, if ectopic Myc is present in our lung tumor mouse model. Moreover, in the liver of these mice with both oncogenes metastases are found. If E-cadherin function is impaired in our RAF-dependent lung tumor model, a switch from adenoma to adenocarcinoma occurs and genes characteristic for the early endodermal lineage are expressed. Based on these data I propose a novel model of metastasis and describe its implications. The hallmark of the model is the induction of a state of plasticity in tumor cells, which allows the reversal of differentiation to an earlier point in their ontogenic history

    Comprehensive Interpretation of Thermal Dileptons at the SPS

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    Employing thermal dilepton rates based on medium-modified electromagnetic correlation functions we show that recent dimuon spectra of the NA60 collaboration in central In-In collisions at the CERN-SPS can be understood in terms of radiation from a hot and dense hadronic medium. Earlier calculated \rho-meson spectral functions, as following from hadronic many-body theory, provide an accurate description of the data up to dimuon invariant masses of about M\simeq 0.9 GeV, with good sensitivity to details of the predicted \rho-meson line shape. This, in particular, identifies baryon-induced effects as the prevalent ones. We show that a reliable description of the \rho contribution opens the possibility to study further medium effects: at higher masses (M \simeq 0.9-1.5 GeV) 4-pion type annihilation is required to account for the experimentally observed excess indicating precursor effects of chiral symmetry restoration (``chiral mixing''), while remaining structures in the \omega and \phi region are suggestive for modifications in their line shapes as well.Comment: 4 pages, 4 figures, v2: slightly improved estimate of four-pion contributions; accepted for publication in Phys. Rev. Let

    Theoretical Overview on (Hidden) Charm in High-Energy Heavy-Ion Collisions

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    Recent developments in the theoretical evaluation of charmonium production in ultrarelativistic heavy-ion collisions (URHIC's) are discussed. In particular, the consequences of equilibrium properties of open and hidden charm states -- accessible, {\it e.g.}, in QCD lattice gauge calculations -- are assessed. These include abundances as well as formation and dissociation rates of charmonia in both hadronic and quark-gluon matter.Comment: Invited Talk at 7. Int. Conf. on Strangeness in Quark Matter (Atlantic Beach, NC, USA, 12.-17.03.03); 10 pages LaTeX including 11 Figures and iop style files; v3: Section 3.4 (Continuity) revise