Showing papers by "Carlos A. Bertulani published in 2022"

Unsupervised machine learning correlations in EoS of neutron stars

Abstract: Neutron stars are compact objects of large interest in the nuclear astrophysics community. The extreme conditions present in such systems impose big challenges to our current microscopic models of nuclear structure. Equation of states (EoS) are frequently derived from sophisticated quantum mechanical models, such as: relativistic, non-relativistic and many mean-field approaches. Every single model, in general, contains many parameters such as the NN interaction strength, particle compositions, etc. These are particular features of each model and can be represented by numbers and categories in a machine learning context. Different choices of features will affect EoS properties leading to different macroscopic properties of the star. In this work we analyze a selection of EoS containing a variety of different physics models. One of our objectives is to develop tools that enable a better understanding of the correlations among the different model features and the outcome produced by them when employed to model neutron stars.

A new Time-of-flight detector for the R$$^3$$B setup

Abstract: Abstract We present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R $$^3$$ 3 B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision $$\sigma _{\varDelta E}/{\varDelta E}$$ σ Δ E / Δ E of up to 1% and a time precision of up to 14 ps (sigma). Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible.

Cluster Structures with Machine Learning Support in Neutron Star M-R relations

Abstract: Neutron stars (NS) are compact objects with strong gravitational fields, and a matter composition subject to extreme physical conditions. The properties of strongly interacting matter at ultra-high densities and temperatures impose a big challenge to our understanding and modelling tools. Some difficulties are critical, since one cannot reproduce such conditions in our laboratories or assess them purely from astronomical observations. The information we have about neutron star interiors are often extracted indirectly, e.g., from the star mass-radius relation. The mass and radius are global quantities and still have a significant uncertainty, which leads to great variability in studying the micro-physics of the neutron star interior. This leaves open many questions in nuclear astrophysics and the suitable equation of state (EoS) of NS. Recently, new observations appear to constrain the mass-radius and consequently has helped to close some open questions. In this work, utilizing modern machine learning techniques, we analyze the NS mass-radius (M-R) relationship for a set of EoS containing a variety of physical models. Our objective is to determine patterns through the M-R data analysis and develop tools to understand the EoS of neutron stars in forthcoming works.

Silicon tracker array for RIB experiments at SAMURAI

Abstract: This work describes a silicon tracker system developed for experiments with proton-rich radioactive ion beams at the SAMURAI superconducting spectrometer of RIBF at RIKEN. The system is designed for accurate angular reconstruction and atomic number identification of relativistic heavy ions and protons which are simultaneously produced in reactions motivated by studies of proton capture reactions of interest for nuclear astrophysics. The technical characteristics of the tracking array are described in detail as are its performance in two pilot experiments. The physics justification for such a system is also presented.

Big Bang nucleosynthesis as a probe of new physics

Abstract: The Big Bang Nucleosynthesis (BBN) model is a cornerstone for the understanding of the evolution of the early universe, making seminal predictions that are in outstanding agreement with the present observation of light element abundances in the universe. Perhaps, the only remaining issue to be solved by theory is the so-called “lithium abundance problem". Dedicated experimental efforts to measure the relevant nuclear cross sections used as input of the model have lead to an increased level of accuracy in the prediction of the light element primordial abundances. The rise of indirect experimental techniques during the preceding few decades has permitted the access of reaction information beyond the limitations of direct measurements. New theoreticaldevelopments have also opened a fertile ground for tests of physics beyond the standard model of atomic,nuclear, statistics, and particle physics. We review the latest contributions of our group for possible solutions of the lithium problem.

Nuclear Spectroscopy with Heavy Ion Nucleon Knockout and (p,2p) Reactions

Abstract: Knockout reactions with heavy ion targets in inverse kinematics, as well as “quasi-free” (p,2p) and (p,pn) reactions are useful tools for nuclear spectroscopy. We report calculations on ab-initio many-body wavefunctions based on the no-core shell model to study the nucleon removal reactions in light nuclei, including beryllium, carbon, and oxygen isotopic chains, and explore the importance of using an ab-initio method. Our study helps clarifying how the extraction of spectroscopic factors from the experiments depend on the details of the many-body wavefunctions being probed. We show that recent advances with the ab-initio method can provide more insights on the spectroscopy information extracted from experiments.

Nuclear fragmentation reactions as a probe of neutron skins in nuclei

Abstract: We investigate the contributions of various reaction channels to the interaction, reaction, charge-changing and neutron-changing cross sections. The goal is to investigate the relation between microscopic interactions and the symmetry energy component of the equation of state (EoS) of interest for the structure of neutron stars. We compare the neutron skins extracted from diverse experimental techniques with those obtained with Hartree–Fock–Bogoliubov calculations using 23 Skyrme and with eight density-dependent interactions used in the relativistic mean-field method. We show that no particular conclusion can be drawn on the best EoS in view of the wide range of uncertainty in the experimental data. We further investigate the prospects of using neutron-changing reactions to assess the isospin dependence of the neutron skin in neutron-rich nuclei.

Isotopic cross sections of fragmentation residues produced by light projectiles on carbon near 400A MeV

Abstract: We measured 135 cross sections of residual nuclei produced in fragmentation reactions of 12 C, 14 N, and 13 − 16 , 20 , 22 O projectiles impinging on a carbon target at kinetic energies of near 400 A MeV, most of them for the first time, with the R 3 B / LAND setup at the GSI facility in Darmstadt (Germany). The use of this state-of-the-art experimental setup in combination with the inverse kinematics technique gave the full identification in atomic and mass numbers of fragmentation residues with a high precision. The cross sections of these residues were determined with uncertainties below 20% for most of the cases. These data are compared to other previous measurements with stable isotopes and are also used to benchmark different model calculations.

1998 Isospin structure of one- and two-phonon GDR excitations

Abstract: Isospin is included in the description of Coulomb excitation of multiple giant isovector dipole resonances. In the excitation of even-even nuclei, a relevant portion of the excitation strength is shown to be associated with 1 + two-phonon states, which tends to be hindered or completely supressed in calculations in which the isospin degree of freedom is not considered. We find that the excitation cross sections is strongly dependent on the ground state isospin.

Ii. production of h with antiproton beams

Abstract: The production of antihydrogen in flight in p-nucleus collisions is calculated theoretically in the Plane Wave Born Approximation (which is equivalent to the straight line semiclassical approximation). Antihydrogen has been produced in this way at LEAR/CERN [1] and is presently studied at FERMILAB at various p energies. Dirac wave functions for the leptons are used, taking first order (Zα) corrections into account. Analytical results are obtained for differential cross-sections. Total cross sections are obtained by numerical integration. The dependence on the transverse momentum transfer is studied and the accuracy of the equivalent photon approximation and a recent variant by Munger, Brodsky,and Schmidt [2] is discussed as a function of beam energy.

Bayesian Inference of Phenomenological EoS of Neutron Stars with Recent Observations

Abstract: The description of stellar interiors remains as a big challenge for the nuclear astrophysics community. The consolidated knowledge is restricted to density regions around the saturation of hadronic matter ρ 0 = 2 . 8 × 10 14 g cm − 3 , regimes where our nuclear models are sucessfully applied. As one moves towards higher densities and extreme conditions up to five to twenty times ρ 0 , little can be said about the microphysics of such obejects. Here, we employ an MCMC strategy in order to acess the variability of polytropic three-pircewised models for neutron star equation of states. With a fixed description of the hadronic matter we explore a variety of models for the high density regimes leading to stellar masses up to 2.5 M (cid:12) . In addition, we also discuss the use of a Bayesian power regression model with heteroscedastic error. The set of EoS from LIGO was used as inputs and treated as data set for testing case.

Direct Nuclear Reactions

Abstract: C.A. Bertulani ∗ and A. Bonaccorso † Department of Physics and Astronomy, Texas A&M University-Commerce, Commerce, TX 75429, USA INFN, Sez. di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy Direct nuclear reactions occur in a characteristic time of 10−22 s, the time it takes a nucleon to cross the nucleus. The short time only allows for the interaction with one or a few nucleons. Contrary to compound nucleus products, the direct reaction products are not distributed isotropically, but are focused in the forward direction. In this brief review we discuss the basic theoretical concepts used in the experimental studies of the most common cases of direct reactions such as (a) elastic scattering, (b) inelastic scattering, (c) Coulomb excitation, (d) transfer reactions and (e) breakup reactions. A recommended list of references, which will help the reader of this short and scope-limited review are [1–5].

0 70 20 87 v 2 1 0 A pr 2 00 7 Electro-disintegration following beta-decay

Abstract: The disintegration of weakly bound nuclei with small neutron separation energy in stars can impose limits to the stellar scenario where these nuclei exist. Beta-decay already sets stringent limits on the existence of nuclei very far from the line of stability (see, e.g. [1]). Here I discuss an additional effect, namely the restrictions imposed by final state interactions of the beta-particle with the daughter nucleus. Electrons observed in beta-decay can have enough kinetic energy to induce the dissociation of the daughter nucleus with small separation energy. If this process is proven to be relevant, it would lead to the existence of voids in the elemental abundance close to the drip-line. The basic assumptions adopted here are that the excitation (dissociation) of a nucleus following beta-decay is sequential and that it can be described as a two-step process, so that the transition rate is given by

B rem sstrahlung radiation by a tunneling particle

Abstract: W e study the brem sstrahlung radiation of a tunneling charged particle in a tim e-dependent picture. In particular, we treat the case of brem sstrahlung during alpha-decay, which has been suggested as a prom issing toolto investigate the problem oftunneling tim es. W e show deviations ofthe num ericalresults from the sem iclassicalestim ates. A standard assum ption ofa preform ed particle inside the wellleads to sharp high-frequency lines in the brem sstrahlung em ission. These linescorrespond to\quantum beats" oftheinternalpartofthewavefunction duringtunnelingarising from the interference ofthe neighboring resonancesin the well.