126,491 research outputs found

    K/K+K^-/K^+ ratios in relativistic heavy-ion collisions

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    We study K/K+K^-/K^+ ratios as a function of centrality (participant nucleon number), transverse mass (mtm_t), and rapidity, in heavy-ion collisions at beam energies between 1A and 2A GeV. We use the relativistic transport model that includes expicitly the strangeness degrees of freedom and consider two scenarios for kaon properties in dense matter, one with and one without medium modifications of their properties. In both scenarios, The K/K+K^-/K^+ ratio does not change very much with the centrality, while the K/πK/\pi and Kˉ/π{\bar K}/\pi ratios increase with increasing centrality. Significant differences are predicted, both in magnitudes and shapes, for the mtm_t spectra and rapidity distributions of K/K+K^-/K^+ ratio. Experimental measurement of these ratios, currently under investigation by the FOPI, KaoS, E866, and E895 collaborations, will be useful in revealing the kaon in-medium properties.Comment: RevTex, 10 pages, including 17 postscript figures, submitted to Phys. Rev.

    Comparison of Models of Critical Opacity in the Quark-Gluon Plasma

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    In this work we discuss two methods of calculation of quark propagation in the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model. The essential difference of these calculations is the treatment of deconfinement. A model of confinement is not included in the work of Gastineau, Blanquier and Aichelin [hep-ph/0404207], however, the meson states they consider are still bound for temperatures greater than the deconfinement temperature T_c. On the other hand, our model deals with unconfined quarks and includes a description of the q(bar)q resonances found in lattice QCD studies that make use of the maximum entropy method (MEM). We compare the q{bar)q cross sections calculated in these models.Comment: 7 pages and 4 figures RevTe

    Study of Strangeness Condensation by Expanding About the Fixed Point of the Harada-Yamawaki Vector Manifestation

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    Building on, and extending, the result of a higher-order in-medium chiral perturbation theory combined with renormalization group arguments and a variety of observations of the vector manifestation of Harada-Yamawaki hidden local symmetry theory, we obtain a surprisingly simple description of kaon condensation by fluctuating around the "vector manifestation (VM)" fixed point identified to be the chiral restoration point. Our development establishes that strangeness condensation takes place at about 3 n_0 where n_0 is nuclear matter density. This result depends only on the renoramlization-group (RG) behavior of the vector interactions, other effects involved in fluctuating about the bare vacuum in so many previous calculations being "irrelevant" in the RG about the fixed point. Our results have major effects on the collapse of neutron stars into black holes.Comment: 4 page

    The Fate of Hadron Masses in Dense Matter: Hidden Local Symmetry and Color Flavor Locking

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    The notion that hadron masses scale according to the scaling of the quark condensate in hadronic matter, partly supported by a number of observations in finite nuclei, can be interpreted in terms of Harada-Yamawaki's ``vector manifestation" (VM) of chiral symmetry. In this scenario, near chiral restoration, the vector meson masses drop to zero {\it in the chiral limit} with vanishing widths. This scenario appears to differ from the standard linear sigma model scenario. We exploit a link between the VM and color-flavor locking inferred by us from lattice data on quark number susceptibility (QNS) measured as a function of temperature to suggest that local flavor symmetry gets mapped to color gauge symmetry at the chiral phase transition.Comment: 5 pages, revised with title change, sharpened arguments and updated reference

    Double Decimation and Sliding Vacua in the Nuclear Many-Body System

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    We propose that effective field theories for nuclei and nuclear matter comprise of "double decimation": (1) the chiral symmetry decimation (CSD) and (2) Fermi liquid decimation (FLD). The Brown-Rho scaling recently identified as the parametric dependence intrinsic in the "vector manifestation" of hidden local symmetry theory of Harada and Yamawaki results from the first decimation. This scaling governs dynamics down to the scale at which the Fermi surface is formed as a quantum critical phenomenon. The next decimation to the top of the Fermi sea where standard nuclear physics is operative makes up the Fermi liquid decimation. Thus nuclear dynamics is dictated by two fixed points, namely, the vector manifestation fixed point and the Fermi liquid fixed point. It has been a prevalent practice in nuclear physics community to proceed with the second decimation only, assuming density independent masses. We show why most nuclear phenomena can be reproduced by theories using either density-independent, or density-dependent masses, a grand conspiracy of nature that is an aspect that could be tied to the Cheshire-Cat phenomenon in hadron physics. We identify what is left out in the Fermi liquid decimation that does not incorporate the CSD. Experiments such as the dilepton production in relativistic heavy ion reactions, which are specifically designed to observe effects of dropping masses, could exhibit large effects from the reduced masses. However they are compounded with effects that are not directly tied to chiral symmetry. We discuss a recent STAR/RHIC observation where BR scaling can be singled out in a pristine environment.Comment: Latex, 9 figures; based on version prepared for Phys. Re

    Matching the QCD and Hadron Sectors and Medium Dependent Meson Masses; Hadronization in Relativistic Heavy Ion Collisions

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    The recent developments on the "vector manifestation" of chiral symmetry by Harada and Yamawaki provide a compelling evidence for, and "refine," the in-medium scaling of hadronic properties in dense/hot matter (call it ``BR scaling") proposed by the authors in 1991. We reinterpret the Harada-Yamawaki result obtained in a Wilsonian renormalization-group approach to hidden local symmetry theory matched to QCD at near the chiral scale in terms of the Nambu-Jona-Lasinio model and predict that the vector meson mass in medium should scale m_\rho^\star/m_\rho\sim (\la\bar{q}q\ra^\star/\la\bar{q}q\ra)^{1/2} from n=0n=0 up to n=n0\sim n=n_0 (where n0n_0 is nuclear matter density) and then go over to the linear scaling m_\rho^\star/m_\rho\sim \la\bar{q}q\ra^\star/\la\bar{q}q\ra up to the chiral transition density ncn_c at which the mass is to vanish (in the chiral limit) according to the vector manifestation fixed point. In the regime of the linear scaling above n0n_0, the (vector) gauge coupling constant should fall linearly in \la\bar{q}q\ra^\star, vanishing at the critical point, with the width of the vector meson becoming steeply narrower. We suggest the in-medium vector meson mass, {\em both} parametric and pole, which goes smoothly to zero with increasing density, to be an order parameter for chiral symmetry restoration. Some issues related to recent RHIC observations are qualitatively discussed in the appendices. Our main conclusion that follows from these considerations is that the movement towards chiral restoration can be reliably described in Nambu-Jona-Lasinio mean field, with constituent quarks as variables, although there is probably density discontinuity following chiral restoration.Comment: Contribution to the Hidenaga Yamagishi Commemorative Volume edited by E. Witten and I.Zahe