894 research outputs found
Isospin Symmetry Breaking and the -System
Simple quark models for the low lying vector mesons suggest a mixing between
the u- and d-flavors and a violation of the isospin symmetry for the
- system much stronger than observed. It is shown that the chiral
dynamics, especially the QCD anomaly, is responsible for a restoration of the
isospin symmetry in the -system.Comment: 4 pages, espcrc2.st
Angle-resolved photoemission in doped charge-transfer Mott insulators
A theory of angle-resolved photoemission (ARPES) in doped cuprates and other
charge-transfer Mott insulators is developed taking into account the realistic
(LDA+U) band structure, (bi)polaron formation due to the strong electron-phonon
interaction, and a random field potential. In most of these materials the first
band to be doped is the oxygen band inside the Mott-Hubbard gap. We derive the
coherent part of the ARPES spectra with the oxygen hole spectral function
calculated in the non-crossing (ladder) approximation and with the exact
spectral function of a one-dimensional hole in a random potential. Some unusual
features of ARPES including the polarisation dependence and spectral shape in
YBa2Cu3O7 and YBa2Cu4O8 are described without any Fermi-surface, large or
small. The theory is compatible with the doping dependence of kinetic and
thermodynamic properties of cuprates as well as with the d-wave symmetry of the
superconducting order parameter.Comment: 8 pages (RevTeX), 10 figures, submitted to Phys. Rev.
An Ultrafast Linear Array Detector for Single-Shot Electro-Optical Bunch Profile Measurements
An Ultrafast Linear Array Detector for Single-Shot Electro-Optical Bunch Profile Measurements
Isotopic composition of fragments in multifragmentation of very large nuclear systems: effects of the chemical equilibrium
Studies on the isospin of fragments resulting from the disassembly of highly
excited large thermal-like nuclear emitting sources, formed in the ^{197}Au +
^{197}Au reaction at 35 MeV/nucleon beam energy, are presented. Two different
decay systems (the quasiprojectile formed in midperipheral reactions and the
unique source coming from the incomplete fusion of projectile and target in the
most central collisions) were considered; these emitting sources have the same
initial N/Z ratio and excitation energy (E^* ~= 5--6 MeV/nucleon), but
different size. Their charge yields and isotopic content of the fragments show
different distributions. It is observed that the neutron content of
intermediate mass fragments increases with the size of the source. These
evidences are consistent with chemical equilibrium reached in the systems. This
fact is confirmed by the analysis with the statistical multifragmentation
model.Comment: 9 pages, 4 ps figure
Multifragmentation of charge asymmetric nuclear systems
The multifragmentation of excited spherical nuclear sources with various N/Z
ratios and fixed mass number is studied within dynamical and statistical
models. The dynamical model treats the multifragmentation process as a final
stage of the growth of density fluctuations in unstable expanding nuclear
matter. The statistical model makes a choice of the final multifragment
configuration according to its statistical weight at a global thermal
equilibrium. Similarities and differences in the predictions of the two models
on the isotopic composition of the produced fragments are presented and the
most sensitive observable characteristics are discussed.Comment: 15 pages, 8 figure
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