21 research outputs found
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
Theoretical Optical Potential Derived from Chiral Potentials
No full textElastic 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
Chiral Nucleon-Nucleus Potentials at N3LO
No full textElastic scattering is probably one of the most relevant tools to study nuclear
interactions. In this contribution we study the domain of applicability of microscopic two-body
chiral potentials in the construction of an optical potential. A microscopic complex optical
potential is derived and tested performing calculations on 16 O at different energies. Good
agreement with empirical data is obtained if a Lippmann-Schwinger cutoff at relatively high
energies (above 500 MeV) is employe
Microscopic Optical Potentials: Recent achievements and future perspectives
No full textFew years ago we started the investigation of microscopic Optical Potentials (OP) in the framework of chiral effective field theories [1, 2] and published our results in a series of manuscripts. Starting from the very first work [3], where a microscopic OP was introduced following the multiple scattering procedure of Watson [4], and then followed by Refs. [5, 6], where the agreement with experimental data and phenomenological approaches was successfully tested, we finally arrived at a description of elastic scattering processes off non-zero spin nuclei [7]. Among our achievements, it is worth mentioning the partial inclusion of three-nucleon forces [8], and the extension of our OP to antiproton-nucleus elastic scattering [9]. Despite the overall good agreement with empirical data obtained so far, we do believe that several improvements and upgrades of the present approach are still to be achieved.In this short essay we would like to address some of the most relevant achievements and discuss an interesting development that, in our opinion, is needed to further improve microscopic OPs in order to reach in a near future the same level of accuracy of the phenomenological ones
Ab Initio Computation of Charge Densities for Sn and Xe Isotopes
No full textWe present the first ab initio calculations for open-shell nuclei past the tin isotopic line, focusing on Xe isotopes as well as doubly magic Sn isotopes. We show that, even for moderately hard interactions, it is possible to obtain meaningful predictions and that the NNLOsat chiral interaction predicts radii and charge density distributions close to the experiment. We then make a new prediction for Sn100. This paves the way for ab initio studies of exotic charge density distributions at the limit of the present ab initio mass domain, where experimental data is becoming available. The present study closes the gap between the largest isotopes reachable by ab initio methods and the smallest exotic nuclei accessible to electron scattering experiments
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
Microscopic optical potential derived from N N chiral potentials
No full textA microscopic optical potential is derived from N N chiral potentials at fourth (NLO) and fifth (NLO) order, 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. The numerical predictions of our optical potential are compared with those of a successful phenomeno- logical optical potential and with available empirical data for elastic proton scattering on different isotopic chains and for incident proton energies in the range 156 ≤ E ≤ 333 MeV
Microscopic Optical Potential for Elastic Proton-Nucleus Scattering from Chiral Forces
No full textA microscopic optical potential (OP) is derived from NN chiral potentials at the first-order term within the spectator expansion of the multiple scattering theory and adopting the impulse approximation. The performances of our OP are compared with those of a phenomenological OP in the description of elastic proton scattering data on different isotopic chains. An analogous scheme is adopted to construct a microscopic OP for elastic antiproton-nucleus scattering. The results of our OPs are in reasonably good agreement with the experimental data, for both elastic proton and antiproton-nucleus scatterin
Elastic Antiproton-Nucleus Scattering from Chiral Forces
No full textElastic scattering of antiprotons off He4, C12, and O16,18 is described for the first time with a consistent microscopic approach based on the calculation of an optical potential (OP) describing the antiproton-target interaction. The OP is derived using the recent antiproton-nucleon (p ̄N) chiral interaction to calculate the p ̄N t matrix, while the target densities are computed with the ab initio no-core shell model using chiral interactions as well. Our results are in good agreement with the existing experimental data and the results computed at different chiral orders of the p ̄N interaction display a well-defined convergence pattern
Determination of Nuclear Matter Radii by Means of Microscopic Optical Potentials: The Case of Kr
No full textIn 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
