1,897 research outputs found
The electro production of d* dibaryon
dibaryon study is a critical test of hadron interaction models. The
electro production cross sections of have been calculated based on
the meson exchange current model and the cross section around 30 degree of 1
GeV electron in the laboratory frame is about 10 nb. The implication of this
result for the dibaryon search has been discussed.Comment: 12 pages, 12 figures, Late
Ultrafast Coherent Spectroscopy of the Fermi Edge Singularity
In this work we present a theoretical description of the transient response
of the Fermi Edge Singularity (FES). We study the linear and the nonlinear
response of an n-doped QW to laser pulses in the Coherent Control (CC) and Four
Wave Mixing (FWM) Configurations. By means of a bosonization formalism we
calculate the FWM signal emitted by the sample when it is excited by pulses
spectrally peaked around the FES and we show that the long time behavior of the
nonlinear signal is very similar to the linear case.Comment: Conference paper (13 EP2DS
Fermionic Atoms in Optical Superlattices
Fermionic atoms in an optical superlattice can realize a very peculiar
Anderson lattice model in which impurities interact with each other through a
discretized set of delocalized levels. We investigate the interplay between
Kondo effect and magnetism under these finite-size features. We find that Kondo
effect can dominate over magnetism depending on the parity of the number of
particles per discretized set. We show how Kondo-induced resonances of
measurable size can be observed through the atomic interference pattern
Exciton Beats in GaAs Quantum Wells: Bosonic Representation and Collective Effects
We discuss light-heavy hole beats observed in transient optical experiments
in GaAs quantum wells in terms of a free-boson coherent state model. This
approach is compared with descriptions based on few-level representations.
Results lead to an interpretation of the beats as due to classical
electromagnetic interference. The boson picture correctly describes photon
excitation of extended states and accounts for experiments involving coherent
control of the exciton density and Rayleigh scattering beating.Comment: 4 pages, no figures. Accepted for publication in Solid State
Communication
Double Pion Photoproduction in Nuclei
The inclusive A(gamma,pi+ pi-)X reaction is studied theoretically. A sizeable
enhancement of the cross section is found, in comparison with the scaling of
the deuteron cross section (sigma_deuteron * A/2). This enhancement is due to
the modifications in the nuclear medium of the gamma N ----> pi pi N amplitude
and the pion dispersion relation. The enhancement is found to be bigger than
the one already observed in the (pi,pi pi) reaction in nuclei.Comment: 11 pages, 7 figures (figures available from authors); TeX, Version
3.141 [PD VMS 3.4/CERN 1.0
Restrictions on the coherence of the ultrafast optical emission from an electron-hole pairs condensate
We report on the transfer of coherence from a quantum-well electron-hole
condensate to the light it emits. As a function of density, the coherence of
the electron-hole pair system evolves from being full for the low density
Bose-Einstein condensate to a chaotic behavior for a high density BCS-like
state. This degree of coherence is transfered to the light emitted in a damped
oscillatory way in the ultrafast regime. Additionally, the photon field
exhibits squeezing properties during the transfer time. We analyze the effect
of light frequency and separation between electron and hole layers on the
optical coherence. Our results suggest new type of ultrafast experiments for
detecting electron-hole pair condensation.Comment: 4 pages,3 figures, to be published in Physical Review Letters. Minor
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