1,720,975 research outputs found
Relativistic Descriptions of Final-State Interactions in Charged-Current Neutrino-Nucleus Scattering at ArgoNeuT Kinematics
Full text linkThe analysis of the recent charged-current neutrino-nucleus scattering cross sections measured by the
ArgoNeuT Collaboration requires relativistic theoretical descriptions also accounting for the role of
final-state interactions. In this work, we evaluate differential neutrino-nucleus cross sections with
the relativistic Green’s function model, where final-state interactions are described in the inclusive
scattering consistently with the exclusive scattering using a complex optical potential. The sensitivity
to the parametrization adopted for the phenomenological optical potential is discussed. The predictions
of the relativistic Green’s function model are compared with the results of different descriptions of final-state
interactions
Theoretical optical potential derived from nucleon-nucleon chiral potentials
Full text linkBackground: Elastic scattering is probably the main event in the interactions of nucleons with nuclei. Even if this
process has been extensively studied over the last years, a consistent description, i.e., starting from microscopic
two- and many-body forces connected by the same symmetries and principles, is still under development.
Purpose: In this work we study the domain of applicability of microscopic two-body chiral potentials in the
construction of an optical potential.
Methods: We basically follow the Kerman, McManus, and Thaler approach [Ann. Phys. (NY) 8, 551 (1959)] to
build a microscopic complex optical potential, and then we perform some test calculations on 16O at different
energies.
Results:. Our conclusion is that a particular set of potentials with a Lippmann–Schwinger cutoff at relatively
high energies (above 500 MeV) reproduces best the scattering observables.
Conclusions: Our work shows that building an optical potential within chiral perturbation theory is a promising
approach for describing elastic proton scattering; in particular, in view of the future inclusion of many-body
forces that naturally arises in such a framework
Determination of Nuclear Matter Radii by Means of Microscopic Optical Potentials: The Case of Kr
Full text linkIn this work we use microscopic Nucleon–Nucleus Optical Potentials (OP) to analyze elastic scattering data for the differential cross section of the 78Kr (p,p) 78Kr reaction, with the goal of extracting the
matter radius and estimating the neutron skin, quantities that are both needed to determine the slope parameter
L of the nuclear symmetry energy. Our analysis is performed with the factorized version of the microscopic
OP obtained in a previous series of papers within the Watson multiple scattering theory at the first order of the
spectator expansion, which is based on the underlying nucleon–nucleon dynamics and is free from phenomenological inputs. Differently from our previous applications, the proton and neutron densities are described with
a two-parameter Fermi (2pF) distribution, which makes the extraction of the matter radius easier and allows
us to make a meaningful comparison with the original analysis, that was performed with the Glauber model.
With standard minimization techniques we performed data analysis and extracted the matter radius and the
neutron skin. Our analysis produces a matter radius of R(rms) m = 4.12 fm, in good agreement with previous
matter radii extracted from 76Kr and 80Kr, and a neutron skin of Rnp −0.1 fm, compatible with a previous
analysis. Our factorized microscopic OP, supplied with 2pF densities, is a valuable tool to perform the analysis
of the experimental differential cross section and extract information such as matter radius and neutron skin.
Without any free parameters it provides a reasonably good description of the experimental differential cross
section for scattering angles up to ≈ 40 degrees. Compared to the Glauber model our OP can be applied to a
wider range of scattering angles and allows one to probe the nuclear systems in a more internal regio
Neutron density distribution and neutron skin thickness of Pb 208
No full textWe present and discuss numerical predictions for the neutron density distribution of Pb-208 using various nonrelativistic and relativistic mean-field models for the nuclear structure. Our results are compared with the very recent pion photoproduction data from Mainz. The parity-violating asymmetry parameter for elastic electron scattering at the kinematics of the PREX experiment at JLab and the neutron skin thickness are compared with the available data. We consider also the dependence between the neutron skin and the parameters of the expansion of the symmetry energy
Toward a Microscopic Description of Nucleus-Nucleus Collisions
Full text linkWe present the first results of a comprehensive microscopic approach to describe nucleus-nucleus elastic collisions by means of an optical potential derived at first order in multiple-scattering theory and computed by folding the projectile and target nuclear densities with the nucleon-nucleon t matrix, which describes the interaction between each nucleon of the projectile and each nucleon of the target. Chiral interactions are consistently used in the calculation of the t matrix and of the nonlocal nuclear densities, which are computed within the ab initio no-core shell model. Cross sections calculated for α collisions on ^{12}C and ^{16}O at projectile energies in the range 100-300 MeV are presented and compared with available data. For momentum transfer q up to about 1.0 fm^{-1} our results are in good agreement with the experimental data, whereas for higher momenta a reduction of the imaginary contributions is needed
Optical potentials derived from nucleon-nucleon chiral potentials at N4LO
No full textBackground: Elastic scattering is probably the main event in the interactions of nucleons with nuclei. Even if
this process has been extensively studied in the past years, a consistent description, i.e., starting from microscopic
two- and many-body forces connected by the same symmetries and principles, is still under development.
Purpose: In a previous paper [M. Vorabbi, P. Finelli, and C. Giusti, Phys. Rev. C 93, 034619 (2016)] we derived
a theoretical optical potential from N N chiral potentials at fourth order (N 3 LO). In the present work we use N N
chiral potentials at fifth order (N 4 LO), with the purpose to check the convergence and to assess the theoretical
errors associated with the truncation of the chiral expansion in the construction of an optical potential.
Methods: Within the same framework and with the same approximations as the previous paper [M. Vorabbi,
P. Finelli, and C. Giusti, Phys. Rev. C 93, 034619 (2016)], the optical potential is derived as the first-order
term within the spectator expansion of the nonrelativistic multiple scattering theory and adopting the impulse
approximation and the optimum factorization approximation.
Results: The pp and np Wolfenstein amplitudes and the cross section, analyzing power, and spin rotation of
elastic proton scattering from 16 O, 12 C, and 40 Ca nuclei are presented at an incident proton energy of 200 MeV.
The results obtained with different versions of chiral potentials at N 4 LO are compared.
Conclusions: Our results indicate that convergence has been reached at N 4 LO. The agreement with the
experimental data is comparable with the agreement obtained in the previous paper [M. Vorabbi, P. Finelli,
and C. Giusti, Phys. Rev. C 93, 034619 (2016)]. We confirm that building an optical potential within chiral
perturbation theory is a promising approach for describing elastic proton-nucleus scattering
Impact of three-body forces on elastic nucleon-nucleus scattering observables
Full text linkBackground: In a previous series of papers we investigated the domain of applicability of chiral potentials to the
construction of a microscopic optical potential (OP) for elastic nucleon-nucleus scattering. The OP was derived
at the first order of the spectator expansion of the Watson multiple scattering theory and its final expression
was a folding integral between the nucleon-nucleon (NN) t matrix and the nuclear density of the target. In the
calculations NN and three-nucleon (3N) chiral interactions were used for the target density and only the NN
interaction for the NN t matrix.
Purpose: The purpose of this work is to achieve another step towards the calculation of a more consistent OP
introducing the 3N force also in the dynamic part of the OP.
Methods: The full treatment of the 3N interaction is beyond our present capabilities. Thus, in the present work
it is approximated with a density dependent NN interaction obtained after the averaging over the Fermi sphere.
In practice, in our model the 3N force acts as a medium correction of the bare NN interaction used to calculate
the t matrix. Even if the 3N force is treated in an approximate way, this method naturally extends our previous
model of the OP and allows a direct comparison of our present and previous results.
Results: We consider as case studies the elastic scattering of nucleons off 12C and 16O. We present results for
the differential cross section and the spin observables for different values of the projectile energy. From the
comparison with the experimental data and with the results of our previous model we assess the importance of
the 3N interaction in the dynamic part of the OP.
Conclusions: Our analysis indicates that the contribution of the 3N force in the t matrix is small for the differential cross section and it is sizable for the spin observables, in particular, for the analyzing power. We find that the
two-pion exchange term is the major contributor to the 3N force. A chiral expansion order-by-order analysis of
the scattering observables confirms the convergence of our results at the next-to-next-to-next-to-leading-order,
as already established in our previous work
Proton-nucleus elastic scattering: Comparison between phenomenological and microscopic optical potentials
No full textBackground: Elastic scattering is a very important process to understand nuclear interactions in finite nuclei. Despite decades of efforts, the goal of reaching a coherent description of this physical process in terms of microscopic forces is still far from being completed. Purpose: In previous papers we derived a nonrelativistic theoretical optical potential from nucleon-nucleon chiral potentials at fourth (N3LO) and fifth order (N4LO). We checked convergence patterns and established theoretical error bands. With this work we study the performances of our optical potential in comparison with those of a successful nonrelativistic phenomenological optical potential in the description of elastic proton scattering data on several isotopic chains at energies around and above 200 MeV. Methods: We use the same framework and the same approximations as adopted in our previous papers, where the nonrelativistic optical potential is derived at the first-order term within the spectator expansion of the multiple scattering theory and adopting the impulse approximation and the optimum factorization approximation. Results: The cross sections and analyzing powers for elastic proton scattering off calcium, nickel, tin, and lead isotopes are presented for several incident proton energies, exploring the range 156≤E≤333 MeV, where experimental data are available. In addition, we provide theoretical predictions for Ni56 at 400 MeV, which is of interest for the future experiments at EXL. Conclusions: Our results indicate that microscopic optical potentials derived from nucleon-nucleon chiral potentials at N4LO can provide reliable predictions for the cross section and the analyzing power both of stable and exotic nuclei, even at energies where the reliability of the chiral expansion starts to be questionable
Theoretical Optical Potential Derived from Chiral Potentials
Full text linkElastic scattering is probably the main event in the interactions of
nucleons with nuclei. Even if this process has been extensively studied in the last
years, a consistent description, i.e. starting from microscopic two- and many-
body forces connected by the same symmetries and principles, is still under
development. In this contribution we study the domain of applicability of mi-
croscopic two-body chiral potentials in the construction of an optical potential.
We basically follow the Kerman, McManus, and Thaler approach to build a mi-
croscopic complex optical potential and then we perform some test calculations
on 16 O at different energies. Our conclusion is that a particular set of potentials
with a Lippmann-Schwinger cutoff at relatively high energies (above 500 MeV)
has the best performances reproducing the scattering observables. Our work
shows that building an optical potential within Chiral Perturbation Theory is a
promising approach to the description of elastic proton scattering, in particular,
in view of the future inclusion of many-body forces that naturally arise in such
framework
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