26,637 research outputs found
Open Quantum Systems. An Introduction
We revise fundamental concepts in the dynamics of open quantum systems in the
light of modern developments in the field. Our aim is to present a unified
approach to the quantum evolution of open systems that incorporates the
concepts and methods traditionally employed by different communities. We
present in some detail the mathematical structure and the general properties of
the dynamical maps underlying open system dynamics. We also discuss the
microscopic derivation of dynamical equations, including both Markovian and
non-Markovian evolutions.Comment: 100 pages, 3 figures. Updated version with typos corrected. Preprint
version of the published boo
One-photon decay of the tetraquark state in a relativistic constituent quark model with infrared confinement
We further explore the consequences of treating the X(3872) meson as a
tetraquark bound state by analyzing its one-photon decay X => \gamma + J/psi in
the framework of our approach developed in previous papers which incorporates
quark confinement in an effective way. To introduce electromagnetism we gauge a
nonlocal effective Lagrangian describing the interaction of the X(3872) meson
with its four constituent quarks by using the P-exponential path-independent
formalism. We calculate the matrix element of the transition X => \gamma+ J/psi
and prove its gauge invariance. We evaluate the X=> \gamma + J/psi decay width
and the longitudinal/transverse composition of the J/psi in this decay. For a
reasonable value of the size parameter of the X(3872) meson we find consistency
with the available experimental data. We also calculate the helicity and
multipole amplitudes of the process, and describe how they can be obtained from
the covariant transition amplitude by covariant projection.Comment: 13 pages, 5 figures. Typos corrected, version matching the one
published in PR
Double giant resonances in deformed nuclei
We report on the first microscopic study of the properties of two-phonon
giant resonances in deformed nuclei. The cross sections of the excitation of
the giant dipole and the double giant dipole resonances in relativistic heavy
ion collisions are calculated. We predict that the double giant dipole
resonance has a one-bump structure with a centroid 0.8 MeV higher than twice
energy for the single giant dipole resonance in the reaction under
consideration. The width of the double resonance equals to 1.33 of that for the
single resonance.Comment: 5 pages, 2 postscript figure
Muon capture by 3He nuclei followed by proton and deuteron production
The paper describes an experiment aimed at studying muon capture by
nuclei in pure and mixtures at various densities. Energy distributions of
protons and deuterons produced via and are measured for the
energy intervals MeV and MeV, respectively. Muon capture
rates, and are obtained using two different analysis methods. The
least--squares methods gives , . The Bayes theorem
gives ,
. The experimental
differential capture rates, and , are compared with theoretical
calculations performed using the plane--wave impulse approximation (PWIA) with
the realistic NN interaction Bonn B potential. Extrapolation to the full energy
range yields total proton and deuteron capture rates in good agreement with
former results.Comment: 17 pages, 13 figures, accepted for publication in PR
A study of the centrally produced baryon-antibaryon systems in pp interactions at 450 GeV/c
A study of the centrally produced ppbar, ppbarpi, ppbarpipi and lambda lambda
channels has been performed in pp collisions using an incident beam momentum of
450 GeV/c. No significant new structures are observed in the mass spectra,
however, important new information on the production dynamics is obtained. A
systematic study of the production properties of these systems has been
performed and it is found that these systems are not produced dominantly by
double Pomeron exchange.Comment: 13 pages, Latex, 4 Figure
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