126,491 research outputs found

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

We study $K^-/K^+$ ratios as a function of centrality (participant nucleon
number), transverse mass ($m_t$), 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 $K^-/K^+$ ratio does
not change very much with the centrality, while the $K/\pi$ and ${\bar K}/\pi$
ratios increase with increasing centrality. Significant differences are
predicted, both in magnitudes and shapes, for the $m_t$ spectra and rapidity
distributions of $K^-/K^+$ 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

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

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

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

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

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 $n=0$ up to $\sim n=n_0$
(where $n_0$ 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 $n_c$ 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 $n_0$, 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

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