20 research outputs found
Optical Potentials Derived from Nucleon-Nucleon Chiral Potentials at N4LO
Background: Elastic 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. Purpose: In a previous paper we derived a theoretical
optical potential from NN chiral potentials at fourth order (N3LO). In the
present work we use NN chiral potentials at fifth order (N4LO), 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: 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 16O, 12C, and 40Ca nuclei are presented at an incident proton
energy of 200 MeV. The results obtained with different versions of chiral
potentials at N4LO are compared. Conclusions: Our results indicate that
convergence has been reached at N4LO. The agreement with the experimental data
is comparable with the agreement obtained in our previous work. We confirm that
building an optical potential within chiral perturbation theory is a promising
approach for describing elastic proton-nucleus scattering.Comment: Physical Review C, in prin
Microscopic Optical Potentials: recent achievements and future perspectives
Few years ago we started the investigation of microscopic Optical Potentials
(OP) in the framework of chiral effective field theories and published our
results in a series of manuscripts. Starting from the very first work, where a
microscopic OP was introduced following the multiple scattering procedure of
Watson, and then followed by more recent works, 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. Among our achievements, it is worth mentioning the partial
inclusion of three-nucleon forces, and the extension of our OP to
antiproton-nucleus elastic scattering. 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.Comment: 8 pages, 4 figures, Conference proceedings of the 13th International
Spring Seminar on Nuclear Physics, Sant'Angelo d'Ischia, May 15-20, 202
Elastic Antiproton-Nucleus Scattering from Chiral Forces
Elastic 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 (pÂŻN) chiral interaction to calculate the pÂŻN 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 pÂŻN interaction display a well-defined convergence pattern
Optical potentials for the rare-isotope beam era
We review recent progress and motivate the need for further developments in
nuclear optical potentials that are widely used in the theoretical analysis of
nucleon elastic scattering and reaction cross sections. In regions of the
nuclear chart away from stability, which represent a frontier in nuclear
science over the coming decade and which will be probed at new rare-isotope
beam facilities worldwide, there is a targeted need to quantify and reduce
theoretical reaction model uncertainties, especially with respect to nuclear
optical potentials. We first describe the primary physics motivations for an
improved description of nuclear reactions involving short-lived isotopes,
focusing on its benefits for fundamental science discoveries and applications
to medicine, energy, and security. We then outline the various methods in use
today to build optical potentials starting from phenomenological, microscopic,
and ab initio methods, highlighting in particular the strengths and weaknesses
of each approach. We then discuss publicly-available tools and resources
facilitating the propagation of recent progresses in the field to
practitioners. Finally, we provide a set of open challenges and recommendations
for the field to advance the fundamental science goals of nuclear reaction
studies in the rare-isotope beam era.Comment: This paper is the outcome of the Facility for Rare Isotope Beams
Theory Alliance (FRIB - TA) topical program "Optical Potentials in Nuclear
Physics" held in March 2022 at FRIB. Its content is non-exhaustive, was
chosen by the participants and reflects their efforts related to optical
potential
Proton inelastic scattering reveals deformation in He-8
A measurement of proton inelastic scattering of He at ~MeV at
TRIUMF shows a resonance at 3.54(6)~MeV with a width of 0.89(11)~MeV. The
energy of the state is in good agreement with coupled cluster and no-core shell
model with continuum calculations, with the latter successfully describing the
measured resonance width as well. Its differential cross section analyzed with
phenomenological collective excitation form factor and microscopic coupled
reaction channels framework consistently reveals a large deformation parameter
= 0.40(3), consistent with no-core shell model predictions of a large
neutron deformation. This deformed double-closed shell at the neutron drip-line
opens a new paradigm.Comment: 9 pages, 5 figures. Accepted for publication in Physics Letters
Relativistic Descriptions of Final-State Interactions in Charged-Current Neutrino-Nucleus Scattering at ArgoNeuT Kinematics
The 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