4,525 research outputs found
Binding-energy independence of reduced spectroscopic strengths derived from (p, 2p) and (p, pn) reactions with nitrogen and oxygen isotopes
A campaign of intermediate energy (300-450 MeV/u) proton-induced nucleon
knockout measurements in inverse kinematics has been recently undertaken at the
R 3 B/LAND setup at GSI. We present a systematic theoretical analysis of these
data with the aim of studying the quenching of the single-particle strengths
and its binding-energy dependence. For that, the measured semi-inclusive (p,
2p) and (p, pn) cross sections are compared with theoretical predictions based
on single-particle cross sections derived from a novel coupled-channels
formalism and shell-model spectroscopic factors. A systematic reduction of
about 20-30% is found, with a very limited dependence on proton-neutron
asymmetry.Comment: 8 pages, 3 figure
Description of the LiLi transfer reaction using structure overlaps from a full three-body model
Recent data on the differential angular distribution for the transfer
reaction Li(p,d)Li at MeV in inverse kinematics are
analysed within the DWBA reaction framework, using the overlap functions
calculated within a three-body model of Li. The weight of the different
Li configurations in the system's ground state is obtained from the
structure calculations unambiguously. The effect of the Li spin in the
calculated observables is also investigated. We find that, although all the
considered models succeed in reproducing the shape of the data, the magnitude
is very sensitive to the content of wave in the Li
ground-state wave function. Among the considered models, the best agreement
with the data is obtained when the Li ground state contains a 31\%
of wave in the -Li subsystem. Although this model takes into
account explicitly the splitting of the and resonances due to the
coupling of the wave to the spin of the core, a similar
degree of agreement can be achieved with a model in which the Li spin is
ignored, provided that it contains a similar p-wave content.Comment: 8 pages, 3 figures. Final versio
Linking structure and dynamics in reactions with Borromean nuclei: the LiLi case
One-neutron removal reactions induced by two-neutron Borromean
nuclei are studied within a Transfer-to-the-Continuum (TC) reaction framework,
which incorporates the three-body character of the incident nucleus. The
relative energy distribution of the residual unbound two-body subsystem, which
is assumed to retain information on the structure of the original three-body
projectile, is computed by evaluating the transition amplitude for different
neutron-core final states in the continuum. These transition amplitudes depend
on the overlaps between the original three-body ground-state wave function and
the two-body continuum states populated in the reaction, thus ensuring a
consistent description of the incident and final nuclei. By comparing different
Li three-body models, it is found that the LiLi
relative energy spectrum is very sensitive to the position of the and
states in Li and to the partial wave content of these
configurations within the Li ground-state wave function. The possible
presence of a low-lying resonance is discussed. The coupling of the
single particle configurations with the non-zero spin of the Li core,
which produces a spin-spin splitting of the states, is also studied. Among the
considered models, the best agreement with the available data is obtained with
a Li model that incorporates the actual spin of the core and contains
31\% of -wave content in the -Li subsystem, in accord
with our previous findings for the Li(p,d)Li transfer reaction,
and a near-threshold virtual state.Comment: 7 pages, 4 figures, submitted to PL
Investigating the 10Li continuum through 9Li(d,p)10Li reactions
The continuum structure of the unbound system Li, inferred from the
LiLi transfer reaction, is reexamined. Experimental data for
this reaction, measured at two different energies, are analyzed with the same
reaction framework and structure models. It is shown that the seemingly
different features observed in the measured excitation energy spectra can be
understood as due to the different incident energy and angular range covered by
the two experiments. The present results support the persistence of the
parity inversion beyond the neutron dripline as well as the splitting of the
well-known low-lying -wave resonance. Furthermore, they provide indirect
evidence that most of the single-particle strength, including possible
resonances, lies at relatively high excitations energies.Comment: accepted for publication in Physics Letters
Reduced sensitivity of the cross sections to the deuteron model beyond adiabatic approximation
It has recently been reported [Phys. Rev. Lett. 117, 162502 (2016)] that (d,
p) cross sections can be very sensitive to the n-p interactions used in the
adiabatic treatment of deuteron breakup with nonlocal nucleon-target optical
potentials. To understand to what extent this sensitivity could originate in
the inaccuracy of the adiabatic approximation we have developed a leading-order
local- equivalent continuum-discretized coupled-channel model that accounts for
non-adiabatic effects in the presence of nonlocality of nucleon optical
potentials. We have applied our model to the astro- physically relevant
reaction AlAl using two different n-p potentials
associated with the lowest and the highest n-p kinetic energy in the
short-range region of their interaction, respectively. Our calculations reveal
a significant reduction of the sensitivity to the high n-p momenta thus
confirming that it is mostly associated with theoretical uncertainties of the
adiabatic approximation itself. The non-adiabatic effects in the presence of
nonlocality were found to be stronger than those in the case of the local
optical potentials. These results argue for extending the analysis of the reactions, measured for spectroscopic studies, beyond the adiabatic
approximation.Comment: 6 pages, 3 figure
Perey-effect in Continuum-Discretized Coupled-Channel description of reactions
The Perey-effect in two-body channels of reactions has been known for
a long time. It arises when the nonlocal two-body deuteron-target and/or
proton-target problem is approximated by a local one, manifesting itself in a
reduction of the scattering channel wave functions in the nuclear interior.
However, the reaction mechanism requires explicit accounting for
three-body dynamics involving the target and the neutron and proton in the
deuteron. Treating nonlocality of the nucleon-target interactions within a
three-body context requires significant effort and demands going beyond the
widely-used adiabatic approximation, which can be done using a
continuum-discretized coupled-channel (CDCC) method. However, the inclusion of
nonlocal interactions into the CDCC description of reactions has not
been developed yet. Here, we point out that, similarly to the two-body nonlocal
case, nonlocality in a three-body channel can be accounted for by introducing
the Perey factors. We explain this procedure and present the first CDCC
calculations to our knowledge including the Perey-effect.Comment: 13 pages, 2 figure
"Terra sigillata hispánica" de los talleres malagueños en el Teatro Romano de Málaga
El presente trabajo se ha centrado en el análisis de la terra sigillata hispánica elaborada
en los talleres malagueños, documentada en las excavaciones realizadas en el Teatro romano de
Málaga y su entorno. La identificación de las pastas de los materiales analizados han permitido
aproximarnos a los distintos puntos de origen de la sigillata hispánica hallada en el principal
edificio público de época romana excavado en la ciudad de Málaga, con un significativo
porcentaje de las producciones elaboradas en los talleres de T.S.H. malagueñosThis article is based on terra sigillata hispanica analysis which taken place at Málaga
workshops and it has been researched on Málaga Roman Theatre and its surroundings. Thanks
to the identification of the pastes of the materials analysed, we have been able to come closer
to SH points of origin which were found in the main public building, belonging to the Roman
period, excavated in the city of malaga. We emphasize the high percentage of pieces made in
Málaga T.S.H workshop
VISIR-VLT high resolution study of the extended emission of four obscured post-AGB candidates
The onset of the asymmetry of planetary nebulae (PNe) is expected to occur
during the late Asymptotic Giant Branch (AGB) and early post-AGB phases of low-
and intermediate-mass stars. Among all post-AGB objects, the most heavily
obscured ones might have escaped the selection criteria of previous studies
detecting extreme axysimmetric structures in young PNe. Since the most heavily
obscured post-AGB sources can be expected to descend from the most massive PN
progenitors, these should exhibit clear asymmetric morphologies. We have
obtained VISIR-VLT mid-IR images of four heavily obscured post-AGB objects
barely resolved in previous Spitzer IRAC observations to analyze their
morphology and physical conditions across the mid-IR. The VISIR-VLT images have
been deconvolved, flux calibrated, and used to construct RGB composite pictures
as well as color and optical depth maps that allow us to study the morphology
and physical properties of the extended emission of these sources. We have
detected extended emission from the four objects in our sample and resolved it
into several structural components that are greatly enhanced in the temperature
and optical depth maps. They reveal the presence of asymmetry in three young
PNe (IRAS 15534-5422, IRAS 17009-4154, and IRAS 18454+0001), where the
asymmetries can be associated with dusty torii and slightly bipolar outflows.
The fourth source (IRAS 18229-1127), a possible post-AGB star, is better
described as a rhomboidal detached shell. The heavily obscured sources in our
sample do not show extreme axisymmetric morphologies. This is at odds with the
expectation of highly asymmetrical morphologies in post-AGB sources descending
from massive PN progenitors. The sources presented in this paper may be
sampling critical early phases in the evolution of massive PN progenitors,
before extreme asymmetries develop.Comment: 9 pages, 4 figure
Descubrimiento automático de mappings en un caso de uso real con altas exigencias de certeza
Los sistemas de integración de información resuelven las diferencias entre las fuentes, en la mayoría de los casos, mediante la creación de mappings, puentes semánticos entre los elementos de las fuentes. Hasta ahora se han propuesto comparadores para generar un conjunto de mappings para cada par de elementos de las fuentes a integrar, y se han realizado estudios experimentales con ellos. El valor añadido del presente trabajo frente a los trabajos experimentales anteriores es que se ha llevado a cabo en un caso real embebido en una aplicación real (en el dominio geográfico) con altas exigencias de certeza
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