2,600 research outputs found
Paramagnonlike excitations and spin diffusion in magnetic resonance studies of copper oxide superconductors
The relaxation function theory for a doped two-dimensional Heisenberg
antiferromagnetic system in the paramagnetic state for all wave vectors through
the Brillouin zone is presented in view of low frequency response of high-
copper oxide superconductors. We deduced the regions of long lifetime [ K] and "overdamped" [ K]
paramagnonlike excitations in the temperature ()-doping index () phase
diagram from plane oxygen nuclear spin-lattice relaxation rate
data in up to optimally doped LaSrCuO thus providing the
regimes for the spin wave concept and the ''overdamped'' mode.Comment: Physical Review B, accepted, in pres
Possibility of cold nuclear compression in antiproton-nucleus collisions
We study the dynamical response of the oxygen-16 nucleus to an incident
antiproton using the Giessen Boltzmann-Uehling-Uhlenbeck microscopic transport
model with relativistic mean fields. A special emphasis is put on the
possibility of a dynamical compression of the nucleus induced by the moving
antiproton. Realistic antibaryon coupling constants to the mean meson fields
are chosen in accordance with empirical data. Our calculations show that an
antiproton embedded in the nuclear interior with momentum less than the nucleon
Fermi momentum may create a locally compressed zone in the nucleus with a
maximum density of about twice the nuclear saturation density. To evaluate the
probability of the nuclear compression in high-energy antiproton-nucleus
collisions, we adopt a two-stage scheme. This scheme takes into account the
antiproton deceleration due to the cascade of antiproton-nucleon rescatterings
inside the nucleus (first stage) as well as the nuclear compression by the slow
antiproton before its annihilation (second stage). With our standard model
parameters, the fraction of antiproton annihilation events in the compressed
zone is about for O collisions at
GeV/c. Finally, possible experimental triggers aimed at selecting such events
are discussed.Comment: 40 pages, 15 figures, new Sect. V on the in-medium modifications of
annihilation, modified conclusions, added references, version accepted in
Phys. Rev.
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