1,320 research outputs found
In-medium broadening of nucleon resonances
We analyze the effects of an in-medium broadening of nucleon resonances on
the exclusive photoproduction of mesons on nuclei as well as on the total
photoabsorption cross sections in a transport calculation. We show that the
resonance widths observed in semi-inclusive photoproduction on nuclei are
insensitive to an in-medium broadening of nucleon resonances. This is due to a
simple effect: the sizeable width of the nuclear surface and Fermi motion.Comment: 4 pages, 3 figures, minor changes in the tex
Model dependence of single-energy fits to pion photoproduction data
Model dependence of multipole analysis has been explored through
energy-dependent and single-energy fits to pion photoproduction data. The MAID
energy-dependent solution has been used as input for an event generator
producing realistic pseudo data. These were fitted using the SAID
parametrization approach to determine single-energy and energy-dependent
solutions over a range of lab photon energies from 200 to 1200 MeV. The
resulting solutions were found to be consistent with the input amplitudes from
MAID. Fits with a -squared per datum of unity or less were generally
achieved. We discuss energy regions where consistent results are expected, and
explore the sensitivity of fits to the number of included single- and
double-polarization observables. The influence of Watson's theorem is examined
in detail.Comment: 12 pages, 8 figure
The Imprint of Gravitational Waves on the Cosmic Microwave Background
Long-wavelength gravitational waves can induce significant temperature
anisotropy in the cosmic microwave background. Distinguishing this from
anisotropy induced by energy density fluctuations is critical for testing
inflationary cosmology and theories of large-scale structure formation. We
describe full radiative transport calculations of the two contributions and
show that they differ dramatically at angular scales below a few degrees. We
show how anisotropy experiments probing large- and small-angular scales can
combine to distinguish the imprint due to gravitational waves.Comment: 11 pages, Penn Preprint-UPR-
Schroedinger cat-like states by conditional measurements on a beam-splitter
A scheme for generating Schr\"{o}dinger cat-like states of a single-mode
optical field by means of conditional measurement is proposed. Feeding into a
beam splitter a squeezed vacuum and counting the photons in one of the output
channels, the conditional states in the other output channel exhibit a number
of properties that are very similar to those of superpositions of two coherent
states with opposite phases. We present analytical and numerical results for
the photon-number and quadrature-component distributions of the conditional
states and their Wigner and Husimi functions. Further, we discuss the effect of
realistic photocounting on the states.Comment: 6 figures(divided in subfigures) using a4.st
Sum rule for the backward spin polarizability of the nucleon from a backward dispersion relation
A new sum rule for , the backward spin polarizability of the
nucleon, is derived from a backward-angle dispersion relation. Taking into
account single- and multi-pion photoproduction in the s-channel up to the
energy 1.5 GeV and resonances in the t-channel with mass below 1.5 GeV, it is
found for the proton and neutron that = -39.5 +/- 2.4 and
= 52.5 +/- 2.4, respectively, in units of 10^{-4} fm^4.Comment: 10 pages, 1 figure, revtex. Submitted to Phys. Lett.
Incoherent Photoproduction of -mesons from the Deuteron near Threshold
Incoherent photoproduction of the -meson on the deuteron is studied for
photon energies from threshold to 800 MeV. The dominant contribution, the
N-N amplitude, is described within an isobar model. The final
state interaction derived from the CD-Bonn potential is included and found to
be important for the description of the production cross section close to
threshold. Possible effects from the final state interaction are
discussed.Comment: 11 pages, revtex, including 6 figure
The structure and dynamics of young star clusters: King 16, NGC 1931, NGC 637 and NGC 189
In this paper, using 2MASS photometry, we study the structural and dynamical
properties of four young star clusters viz. King 16, NGC 1931, NGC 637 and NGC
189. For the clusters King 16, NGC 1931, NGC 637 and NGC 189, we obtain the
limiting radii of 7', 12', 6' and 5' which correspond to linear radii of 3.6
pc, 8.85 pc, 3.96 pc and 2.8 pc respectively. The reddening values
obtained for the clusters are 0.85, 0.65--0.85, 0.6 and 0.53 and their true
distances are 1786 pc, 3062 pc, 2270 pc and 912 pc respectively. Ages of the
clusters are 6 Myr, 4 Myr, 4 Myr and 10 Myr respectively. We compare their
structures, luminosity functions and mass functions () to the parameter to study the star
formation process and the dynamical evolution of these clusters. We find that,
for our sample, mass seggregation is observed in clusters or their cores only
when the ages of the clusters are comparable to their relaxation times (). These results suggest mass seggregation due to dynamical effects. The
values of , which characterise the overall mass functions for the
clusters are 0.96 0.11, 1.16 0.18, 0.55 0.14 and 0.66
0.31 respectively. The change in as a function of radius is a good
indicator of the dynamical state of clusters.Comment: Accepted for publication in Astrophysics & Space Scienc
Magnetic properties of exactly solvable doubly decorated Ising-Heisenberg planar models
Applying the decoration-iteration procedure, we introduce a class of exactly
solvable doubly decorated planar models consisting both of the Ising- and
Heisenberg-type atoms. Exact solutions for the ground state, phase diagrams and
basic physical quantities are derived and discussed. The detailed analysis of
the relevant quantities suggests the existence of an interesting quantum
antiferromagnetic phase in the system.Comment: 9 pages, 9 figures, submitted to Physical Review
Secure Mobile Support of Independent Sales Agencies
Sales agents depend on mobile support systems for their daily work. Independent sales agencies, however, are not able to facilitate this kind of mobile support on their own due to their small size and lack of the necessary funds. Since their processes correlate with confidential information and include the initiation and alteration of legally binding transactions they have a high need for security. In this contribution we first propose an IT-artifact consisting of a service platform that supports multi-vendor sales processes based on previous work. We then analyze use cases of sales representatives of independent sales agencies using this system and derive their security requirements. We then propose a security extension to the IT-artifact and evaluate this extension by comparing it to existing solutions. Our results show that the proposed artifact extension provides a more convenient and secure solution than already existing approaches
Inclusive meson production in peripheral collisions of ultrarelativistic heavy ions
There exist several proposals to use Weizs\"{a}cker-Williams photons
generated by ultrarelativistic heavy ions to produce exotic particles in
fusion reactions. To estimate the background conditions for such
reactions we analyze various mechanisms of meson production in very peripheral
collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besides
fusion they include also electromagnetic interactions
and strong nucleon-nucleon interactions in grazing collisions. All these
processes are characterised by low multiplicities of produced particles.
and events are simulated by corresponding Monte Carlo codes,
RELDIS and FRITIOF. In each of these processes a certain fraction of pions is
produced close to the mid-rapidity region that gives a background for the
events. The possibility of selecting mesons produced in
fusion events via different cut procedures is
demonstrated.Comment: 27 pages with 4 eps-figures included, uses axodraw.sty Tab.2 and 3
correcte
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