47,435 research outputs found
Dilepton Production at Fermilab and RHIC
Some recent results from several fixed-target dimuon production experiments
at Fermilab are presented. In particular, we discuss the use of Drell-Yan data
to determine the flavor structure of the nucleon sea, as well as to deduce the
energy-loss of partons traversing nuclear medium. Future dilepton experiments
at RHIC could shed more light on the flavor asymmetry and possible
charge-symmetry-violation of the nucleon sea. Clear evidence for scaling
violation in the Drell-Yan process could also be revealed at RHIC.Comment: 5 pages, talk presented at the RIKEN-BNL Workshop on 'Hard Parton
Physics in Nucleus-Nucleus collisions, March 199
Experimental Demonstration of Quantum State Multi-meter and One-qubit Fingerprinting in a Single Quantum Device
We experimentally demonstrate in NMR a quantum interferometric multi-meter
for extracting certain properties of unknown quantum states without resource to
quantum tomography. It can perform direct state determinations,
eigenvalue/eigenvector estimations, purity tests of a quantum system, as well
as the overlap of any two unknown quantum states. Using the same device, we
also demonstrate one-qubit quantum fingerprinting
The scattering of a cylindrical invisibility cloak: reduced parameters and optimization
We investigate the scattering of 2D cylindrical invisibility cloaks with
simplified constitutive parameters with the assistance of scattering
coefficients. We show that the scattering of the cloaks originates not only
from the boundary conditions but also from the spatial variation of the
component of permittivity/permeability. According to our formulation, we
propose some restrictions to the invisibility cloak in order to minimize its
scattering after the simplification has taken place. With our theoretical
analysis, it is possible to design a simplified cloak by using some peculiar
composites like photonic crystals (PCs) which mimic an effective refractive
index landscape rather than offering effective constitutives, meanwhile
canceling the scattering from the inner and outer boundaries.Comment: Accepted for J. Phys.
Hubble Space Telescope H-Band Imaging Survey of Massive Gas-Rich Mergers
We report the results from a deep HST NICMOS H-band imaging survey of a
carefully selected sample of 33 luminous, late-stage galactic mergers at z <
0.3. Signs of a recent galactic interaction are seen in all of the objects in
the HST sample, including all 7 IR-excess Palomar-Green (PG) QSOs in the
sample. Unsuspected double nuclei are detected in 5 ULIRGs. A detailed
two-dimensional analysis of the surface brightness distributions in these
objects indicates that the great majority (81%) of the single-nucleus systems
show a prominent early-type morphology. However, low-surface-brightness
exponential disks are detected on large scale in at least 4 of these sources.
The hosts of 'warm' AGN-like systems are of early type and have less pronounced
merger-induced morphological anomalies than the hosts of cool systems with
LINER or HII region-like nuclear optical spectral types. The host sizes and
luminosities of the 7 PG~QSOs in our sample are statistically indistinguishable
from those of the ULIRG hosts. In comparison, highly luminous quasars, such as
those studied by Dunlop et al. (2003), have hosts which are larger and more
luminous. The hosts of ULIRGs and PG QSOs lie close to the locations of
intermediate-size (about 1 -- 2 L*) spheroids in the photometric projection of
the fundamental plane of ellipticals, although there is a tendency in our
sample for the ULIRGs with small hosts to be brighter than normal spheroids.
Excess emission from a young stellar population in the ULIRG/QSO hosts may be
at the origin of this difference. Our results provide support for a possible
merger-driven evolutionary connection between cool ULIRGs, warm ULIRGs, and
PG~QSOs although this sequence may break down at low luminosity. (abridged)Comment: Paper to be published in the Astrophysical Journal; revised based on
comments from referee. A PDF file combining both text and figures is
available at http://www.astro.umd.edu/~veilleux/pubs/nicmos.pd
Quantum vortices and trajectories in particle diffraction
We investigate the phenomenon of the diffraction of charged particles by thin
material targets using the method of the de Broglie-Bohm quantum trajectories.
The particle wave function can be modeled as a sum of two terms
. A thin separator exists between the
domains of prevalence of the ingoing and outgoing wavefunction terms. The
structure of the quantum-mechanical currents in the neighborhood of the
separator implies the formation of an array of \emph{quantum vortices}. The
flow structure around each vortex displays a characteristic pattern called
`nodal point - X point complex'. The X point gives rise to stable and unstable
manifolds. We find the scaling laws characterizing a nodal point-X point
complex by a local perturbation theory around the nodal point. We then analyze
the dynamical role of vortices in the emergence of the diffraction pattern. In
particular, we demonstrate the abrupt deflections, along the direction of the
unstable manifold, of the quantum trajectories approaching an X-point along its
stable manifold. Theoretical results are compared to numerical simulations of
quantum trajectories. We finally calculate the {\it times of flight} of
particles following quantum trajectories from the source to detectors placed at
various scattering angles , and thereby propose an experimental test of
the de Broglie - Bohm formalism.Comment: 17 pages, 7 figures, accepted by IJB
Neutron Transversity at Jefferson Lab
Nucleon transversity and single transverse spin asymmetries have been the
recent focus of large efforts by both theorists and experimentalists. On-going
and planned experiments from HERMES, COMPASS and RHIC are mostly on the proton
or the deuteron. Presented here is a planned measurement of the neutron
transversity and single target spin asymmetries at Jefferson Lab in Hall A
using a transversely polarized He target. Also presented are the results
and plans of other neutron transverse spin experiments at Jefferson Lab.
Finally, the factorization for semi-inclusive DIS studies at Jefferson Lab is
discussed.Comment: 8 pages, 2 figures, proceedings of Como Transversity05 Worksho
Nonclassical photon pairs generated from a room-temperature atomic ensemble
We report experimental generation of non-classically correlated photon pairs
from collective emission in a room-temperature atomic vapor cell. The
nonclassical feature of the emission is demonstrated by observing a violation
of the Cauchy-Schwarz inequality. Each pair of correlated photons are separated
by a controllable time delay up to 2 microseconds. This experiment demonstrates
an important step towards the realization of the Duan-Lukin-Cirac-Zoller scheme
for scalable long-distance quantum communication.Comment: 4 pages, 2 figure
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