3,522 research outputs found
B Meson Transitions into Higher Mass Charmed Resonances
We use QCD sum rules to estimate the universal form factors describing the
semileptonic B decays into excited charmed resonances, such as the and
states and belonging to the heavy
quark doublet, and the and states and
belonging to the s_\ell^P={5\2}^- doublet.Comment: LaTex, 14 pages, 1 figur
Semileptonic and Rare -meson transitions in a QCD relativistic potential model
Using a QCD relativistic potential model, previously applied to the
calculation of the heavy meson leptonic constants, we evaluate the form factors
governing the exclusive decays , and . In our approach the heavy meson is described as a
bound state, whose wave function is solution of the relativistic Salpeter
equation, with an instantaneous potential displaying Coulombic behaviour at
small distances and linear behaviour at large distances. The light vector meson
is described by using a vector current interpolating field, according to the
Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is
assumed for the quarks not constituting the heavy meson. Our procedure allows
to avoid the description of the light meson in terms of wave function and
constituent quarks, and consequently the problem of boosting the light meson
wave function.
Assuming as an input the experimental results on , we
evaluate all the form factors describing the semileptonic and
rare transitions. The overall comparison with the data, whenever available, is
satisfactory.Comment: Latex, 19 pages, 3 figure
Mid-Infrared Galaxy Morphology Along the Hubble Sequence
The mid-infrared emission from 18 nearby galaxies imaged with the IRAC
instrument on Spitzer Space Telescope samples the spatial distributions of the
reddening-free stellar photospheric emission and the warm dust in the ISM.
These two components provide a new framework for galaxy morphological
classification, in which the presence of spiral arms and their emission
strength relative to the starlight can be measured directly and with high
contrast. Four mid-infrared classification methods are explored, three of which
are based on quantitative global parameters (colors, bulge-to-disk ratio)
similar to those used in the past for optical studies; in this limited sample,
all correlate well with traditional B-band classification. We suggest reasons
why infrared classification may be superior to optical classification.Comment: ApJS (in press), Spitzer Space Telescope Special Issue; 13 pages,
LaTeX (or Latex, etc); Figure 1ab is large, color plate; full-resolution
plates in .pdf format available at
http://cfa-www.harvard.edu/irac/publications
Innovazioni di canale nell\u2019arredamento made in Italy
Il presente capitolo affronta il tema dell\u2019e-commerce nel settore dell\u2019arredamento italiano. Attraverso l\u2019analisi di dati secondari, vengono delineate la situazione attuale, le prospettive future e le principali criticit\ue0 strategiche nel quadro competitivo globale, caratterizzato per il settore da una particolare dinamica innovativa in campo distributivo
Local density of states in metal - topological superconductor hybrid systems
We study by means of the recursive Green's function technique the local
density-of-states of (finite and semi-infinite) multi-band spin-orbit coupled
semiconducting nanowires in proximity to an s-wave superconductor and attached
to normal-metal electrodes. When the nanowire is coupled to a normal electrode,
the zero-energy peak, corresponding to the Majorana state in the topological
phase, broadens with increasing transmission between the wire and the leads,
eventually disappearing for ideal interfaces. Interestingly, for a finite
transmission a peak is present also in the normal electrode, even though it has
a smaller amplitude and broadens more rapidly with the strength of the
coupling. Unpaired Majorana states can survive close to a topological phase
transition even when the number of open channels (defined in the absence of
superconductivity) is even. We finally study the Andreev-bound-state spectrum
in superconductor-normal metal-superconductor junctions and find that in
multi-band nanowires the distinction between topologically trivial and
non-trivial systems based on the number of zero-energy crossings is preserved.Comment: 11 pages, 12 figures, published versio
Entanglement production by quantum error correction in the presence of correlated environment
We analyze the effect of a quantum error correcting code on the entanglement
of encoded logical qubits in the presence of a dephasing interaction with a
correlated environment. Such correlated reservoir introduces entanglement
between physical qubits. We show that for short times the quantum error
correction interprets such entanglement as errors and suppresses it. However
for longer time, although quantum error correction is no longer able to correct
errors, it enhances the rate of entanglement production due to the interaction
with the environment.Comment: 7 pages, 3 figures, published versio
Phase-Dependent Electronic Specific Heat in Mesoscopic Josephson Junctions
We study the influence of superconducting correlations on the electronic
specific heat in a diffusive superconductor-normal metal-superconductor
Josephson junction. We present a description of this system in the framework of
the diffusive-limit Green's function theory, taking into account finite
temperatures, phase difference as well as junction parameters. We find that
proximity effect may lead to a substantial deviation of the specific heat as
compared to that in the normal state, and that it can be largely tuned in
magnitude by changing the phase difference between the superconductors. A
measurement setup to confirm these predictions is also suggested.Comment: 4+ pages, 4 figure
Adiabatic quantum dynamics of a random Ising chain across its quantum critical point
We present here our study of the adiabatic quantum dynamics of a random Ising
chain across its quantum critical point. The model investigated is an Ising
chain in a transverse field with disorder present both in the exchange coupling
and in the transverse field. The transverse field term is proportional to a
function which, as in the Kibble-Zurek mechanism, is linearly
reduced to zero in time with a rate , , starting
at from the quantum disordered phase () and ending
at in the classical ferromagnetic phase (). We first analyze
the distribution of the gaps -- occurring at the critical point --
which are relevant for breaking the adiabaticity of the dynamics. We then
present extensive numerical simulations for the residual energy
and density of defects at the end of the annealing, as a function of
the annealing inverse rate . %for different lenghts of the chain. Both
the average and are found to behave
logarithmically for large , but with different exponents, with , and
. We propose a mechanism for
-behavior of based on the Landau-Zener
tunneling theory and on a Fisher's type real-space renormalization group
analysis of the relevant gaps. The model proposed shows therefore a
paradigmatic example of how an adiabatic quantum computation can become very
slow when disorder is at play, even in absence of any source of frustration.Comment: 10 pages, 11 figures; v2: added references, published versio
Investigation of the quasifission process by theoretical analysis of experimental data of fissionlike reaction products
The fusion excitation function is the important quantity in planning
experiments for the synthesis of superheavy elements. Its values seem to be
determined by the experimental study of the hindrance to complete fusion by the
observation of mass, angular and energy distributions of the fissionlike
fragments. There is ambiguity in establishment of the reaction mechanism
leading to the observed binary fissionlike fragments. The fissionlike fragments
can be produced in the quasifission, fast fission, and fusion-fission processes
which have overlapping in the mass (angular, kinetic energy) distributions of
fragments. The branching ratio between quasifission and complete fusion
strongly depends on the characteristics of the entrance channel. In this paper
we consider a wide set of reactions (with different mass asymmetry and mass
symmetry parameters) with the aim to explain the role played by many quantities
on the reaction mechanisms. We also present the results of study of the
Ca+Bk reaction used to synthesize superheavy nuclei with Z = 117
by the determination of the evaporation residue cross sections and the
effective fission barriers of excited nuclei formed along the
de-excitation cascade of the compound nucleus.Comment: 21 pages, 15 figures, 2 table
- …