522 research outputs found
Chiral Symmetry in Nuclei -- Theoretical Expectations and Hard Facts
It is widely believed that chiral symmetry is restored not only at high
temperatures, but also at high nuclear densities. The drop of the order
parameter of the chiral phase transition, the chiral condensate, with density
has indeed been calculated in various models and is as such a rather robust
result. In this talk I point out that the connection of this property with
actual observables is far less clear. For this task a good hadronic description
of the primary production of hadrons, their propagation inside the nuclear
medium, their decay and the propagation of the decay products through the
medium to the detector all have to be treated with equal accuracy and weight.
In this talk I illustrate with the examples of production and
production how important in particular final state interactions
are.Comment: Invited Talk at Chiral07, Osaka, Japan, Nov. 13 - 16, 200
Development of a Time Projection Chamber Using Gas Electron Multipliers (GEM-TPC)
We developed a prototype time projection chamber using gas electron
multipliers (GEM-TPC) for high energy heavy ion collision experiments. To
investigate its performance, we conducted a beam test with 3 kinds of gases
(Ar(90%)-CH4(10%), Ar(70%)-C2H6(30%) and CF4). Detection efficiency of 99%, and
spatial resolution of 79 m in the pad-row direction and 313 m in the
drift direction were achieved. The test results show that the GEM-TPC meets the
requirements for high energy heavy ion collision experiments. The configuration
and performance of the GEM-TPC are described.Comment: 18 pages, 12 figures, published online in Nucl. Instr. and Meth.
Experimental Signature of Medium Modifications for rho and omega Mesons in the 12 GeV p + A Reactions
The invariant mass spectra of e+e- pairs produced in 12-GeV proton-induced
nuclear reactions are measured at the KEK Proton-Synchrotron. On the low-mass
side of the omega meson peak, a significant enhancement over the known hadronic
sources has been observed. The mass spectra, including the excess, are well
reproduced by a model that takes into account the density dependence of the
vector meson mass modification, as theoretically predicted.Comment: 4 pages, 3 figures, Version accepted for Physical Review Lette
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