459 research outputs found
Dihadron fragmentation: in vacuum and in matter
Two particle correlations within a single jet produced in deeply inelastic
scattering (DIS) off a large nucleus as well as in heavy-ion collisions are
explored. This is performed within the framework of the medium modified
dihadron fragmentation functions. The modification occurs due to gluon
bremsstrahlung induced by multiple scattering. The modified fragmentation
functions for dihadrons are found to follow closely that of single hadrons
leading to a weak nuclear suppression of their ratios as measured by HERMES in
DIS experiments. Meanwhile, a moderate medium enhancement of the near-side
correlation of two high hadrons is found in central heavy-ion collisions,
partially due to trigger bias caused by the competition between parton energy
loss and the initial Cronin effect.Comment: 4 pages, 2 figures, LATEX, talk given at Hard Probes 200
Hard scattering and jets--from p-p collisions in the 1970's to Au+Au collisions at RHIC
Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the
method of leading particles, proved that the partons of Deeply Inelastic
Scattering strongly interacted with each other. Further ISR measurements
utilizing inclusive single or pairs of hadrons established that high pT
particles are produced from states with two roughly back-to-back jets which are
the result of scattering of constituents of the nucleons as described by
Quantum Chromodynamics (QCD), which was developed during the course of these
measurements. These techniques, which are the only practical method to study
hard-scattering and jet phenomena in Au+Au central collisions, are reviewed,
with application to measurements at RHIC.Comment: 4 pages, 5 figures, Proceedings of Hard Probes 2004, International
Conference on Hard and Electromagnetic Probes of High Energy Nuclear
Collisions, Nov 4-10, 2004, to appear in EPJ
The Renyi entropy H_2 as a rigorous, measurable lower bound for the entropy of the interaction region in multiparticle production processes
A model-independent lower bound on the entropy S of the multiparticle system
produced in high energy collisions, provided by the Renyi entropy H_2, is shown
to be very effective. Estimates show that the ratio H_2/S remains close to one
half for all realistic values of the parameters.Comment: Eur. Phys. J. C in print, 17 pages, 5 figure
Radiation induced force between two planar waveguides
We study the electromagnetic force exerted on a pair of parallel slab
waveguides by the light propagating through them. We have calculated the
dependence of the force on the slab separation by means of the Maxwell--Stress
tensor formalism and we have discussed its main features for the different
propagation modes: spatially symmetric (antisymmetric) modes give rise to an
attractive (repulsive) interaction. We have derived the asymptotic behaviors of
the force at small and large separation and we have quantitatively estimated
the mechanical deflection induced on a realistic air-bridge structure.Comment: 10 pages, 6 figure
Bragg spectroscopy of discrete axial quasiparticle modes in a cigar-shaped degenerate Bose gas
We propose an experiment in which long wavelength discrete axial
quasiparticle modes can be imprinted in a 3D cigar-shaped Bose-Einstein
condensate by using two-photon Bragg scattering experiments, similar to the
experiment at the Weizmann Institute [J. Steinhauer {\em et al.}, Phys. Rev.
Lett. {\bf 90}, 060404 (2003)] where short wavelength axial phonons with
different number of radial modes have been observed. We provide values of the
momentum, energy and time duration of the two-photon Bragg pulse and also the
two-body interaction strength which are needed in the Bragg scattering
experiments in order to observe the long wavelength discrete axial modes. These
discrete axial modes can be observed when the system is dilute and the time
duration of the Bragg pulse is long enough.Comment: 5 pages, 3 figures, title, abstract, results changed, references
added. to appear in The European Physical Journal
Transport of a quantum degenerate heteronuclear Bose-Fermi mixture in a harmonic trap
We report on the transport of mixed quantum degenerate gases of bosonic 87Rb
and fermionic 40K in a harmonic potential provided by a modified QUIC trap. The
samples are transported over a distance of 6 mm to the geometric center of the
anti-Helmholtz coils of the QUIC trap. This transport mechanism was implemented
by a small modification of the QUIC trap and is free of losses and heating. It
allows all experiments using QUIC traps to use the highly homogeneous magnetic
fields that can be created in the center of a QUIC trap and improves the
optical access to the atoms, e.g., for experiments with optical lattices. This
mechanism may be cascaded to cover even larger distances for applications with
quantum degenerate samples.Comment: 7 pages, 8 figure
Bright solitons and soliton trains in a fermion-fermion mixture
We use a time-dependent dynamical mean-field-hydrodynamic model to predict
and study bright solitons in a degenerate fermion-fermion mixture in a
quasi-one-dimensional cigar-shaped geometry using variational and numerical
methods. Due to a strong Pauli-blocking repulsion among identical
spin-polarized fermions at short distances there cannot be bright solitons for
repulsive interspecies fermion-fermion interactions. However, stable bright
solitons can be formed for a sufficiently attractive interspecies interaction.
We perform a numerical stability analysis of these solitons and also
demonstrate the formation of soliton trains. These fermionic solitons can be
formed and studied in laboratory with present technology.Comment: 5 pages, 7 figure
L. T. Pease and J. M. Smith
29-1Indian AffairsReport : Petition of L. Pease and J. Smith. [488] Seminole; 1837.1846-1
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