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C. A. Bertulani

Publications and source records attributed to C. A. Bertulani.

At least 163 records · Page 9Linked to original sources
arXiv2005

7Be(p,gamma)8B S-factor from ab initio wave functions

Nuclear structure of 7Be, 8B and 7,8Li is studied within the ab initio no-core shell model (NCSM). Starting from the high-precision CD-Bonn 2000 nucleon-nucleon (NN) interaction, wave functions of 7Be and 8B bound states are obtained in basis spaces up to 10 hbar Omega and used to calculate channel cluster form factors (overlap integrals) of the 8B ground state with 7Be+p. Due to the use of the harmonic oscillator (HO) basis, the overlap integrals have incorrect asymptotic properties. We fix this problem in two alternative ways. First, by a Woods-Saxon (WS) potential solution fit to the interior of the NCSM overlap integrals. Second, by a direct matching with the Whittaker function. The corrected overlap integrals are then used for the 7Be(p,gamma)8B S-factor calculation. We study the convergence of the S-factor with respect to the NCSM HO frequency and the model space size. Our S-factor results are in agreement with recent direct measurement data.

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arXiv2005

Electron scattering on halo nuclei

The inelastic scattering of electrons on weakly-bound nuclei is studied with a simple model based on the long range behavior of the bound state wavefunction and on the effective-range expansion for the continuum wavefunctions. Three mechanisms have been considered: (a) dissociation of halo nuclei by high energy electrons, (b) dissociation by electrons present in a fixed target, and (c) Coulomb dissociation. It is shown that the properties of halo nuclei can be studied in electron-radioactive beam colliders using the electro-disintegration process. A comparison with fixed-target experiments is also performed.

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arXiv2005

Special Relativity and Reactions with Unstable Nuclei

Dynamical relativistic effects are often neglected in the description of reactions with unstable nuclear beams at intermediate energies (E ~ 100 MeV/nucleon). Evidently, this introduces sizable errors in experimental analysis and theoretical descriptions of these reactions. This is particularly important for the experiments held in GANIL/France, MSU/USA, RIKEN/Japan and GSI/Germany. I review a few examples where relativistic effects have been studied in nucleus-nucleus scattering at intermediate energies.

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arXiv2005

Relativistic continuum-continuum coupling in the dissociation of halo nuclei

A relativistic coupled-channels theory for the calculation of dissociation cross sections of halo nuclei is developed. A comparison with non-relativistic models is done for the dissociation of $^{8}$B projectiles. It is shown that neglecting relativistic effects leads to seizable inaccuracies in the extraction of the astrophysical S-factor for the proton+beryllium radiative capture reaction.

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arXiv2004

The stopping of low energy ions in reactions of astrophysical interest

he velocity dependence of the stopping power of swift protons and deuterons in low energy collisions with hydrogen and helium gas targets is investigated with the numerical solution of the time-dependent Schroedinger coupled-channels equations using molecular orbital wavefunctions. At low projectile energies the stopping is mainly due to nuclear stopping, charge exchange of the electron, and excitation of the lowest levels in the target. The second and third mechanisms dominate at E < 200 eV. At lower energies it is also shown that a threshold effect is responsible for a quick drop of the energy loss. This investigation sheds more light on the long standing electron screening problem in fusion reactions of astrophysical interest.

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arXiv2004

Electronic stopping in astrophysical fusion reactions

The stopping power of protons and deuterons in low energy collisions with helium gas targets is investigated with the numerical solution of the time-dependent Schrödinger coupled-channels equations using molecular orbital wavefunctions. It is shown that at low projectile energies the energy loss is mainly due to nuclear stopping, charge exchange, and the excitation of low energy levels in the target. The second and third mechanisms, called electronic stopping, dominate for E>200 eV. At lower energies it is also shown that a threshold effect is responsible for a quick drop of the energy loss. This investigation sheds more light on the long standing electron screening problem in fusion reactions of astrophysical interest.

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arXiv2003

Proton-tetraneutron elastic scattering

We analyze the elastic scattering of protons on a 4n system. This was used as part of the detection technique of a recent experiment [1] to search for the 4n (tetraneutron) as a bound particle. We show that it is unlikely that this process alone could yield the events reported in ref. [1], unless the 4n has an anomalously large backward elastic scattering amplitude.

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arXiv2003

Is the tetraneutron a bound dineutron-dineutron molecule?

In light of a new experiment which claims a positive identification, we discuss the possible existence of the tetraneutron. We explore a novel model based on a dineutron-dineutron molecule. We show that this model is not able to explain the tetraneutron as a bound state, in agreement with other theoretical models already discussed in the literature.

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arXiv2003

Intermediate energy Coulomb excitation as a probe of nuclear structure at radioactive beam facilities

The effects of retardation in the Coulomb excitation of radioactive nuclei in intermediate energy collisions (Elab ~100 MeV/nucleon) are investigated. We show that the excitation cross sections of low-lying states in 11Be, {38,40,42}S and {44,46}Ar projectiles incident on gold and lead targets are modified by as much as 20% due to these effects. The angular distributions of decaying gamma-rays are also appreciably modified.

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arXiv2003

Radiative capture cross sections: challenges and solutions

Radiative capture reactions are one of the main inputs in stellar modelling. In numerous situations, the low energies at which these reactions occur in stars are not accessible with present experimental techniques. Electron screening is one of the major causes of problems in separating the bare cross sections from the screened ones. Indirect experimental techniques have been proposed and are now one of the main tools to obtain these cross sections. I discuss the electron screening problem and the latest progresses obtained with indirect methods.

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arXiv2003

RADCAP: a potential model tool for direct capture reactions

A computer program is presented aiming at the calculation of bound and continuum states, reduced transition probabilities, phase-shifts, photo-disintegration cross sections, radiative capture cross sections, and astrophysical S-factors, for a two-body nuclear system. The code is based on a potential model of a Woods-Saxon, a Gaussian, or a M3Y, type. It can be used to calculate nuclear reaction rates in numerous astrophysical scenarios.

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arXiv2003

Fingerprints of entangled states in reactions with rare isotopes

We study the presence of entangled states of nucleon pairs from nuclear decays and in reactions with exotic nuclei, e.g., 11Li, or 6He. It is shown that the fingerprints of entangled states in these subsystems are visible in correlation measurements and can be accessed with present experimental techniques. This shows that not only atomic and optical systems, but also nuclear systems serve as important tools to obtain dichotomic outcomes for tests of the Einstein-Podolsky-Rosen paradox.

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arXiv2002

A computer program for nuclear scattering at intermediate and high energies

A computer program is presented which calculates the elastic and inelastic scattering in intermediate and high energy nuclear collisions. A coupled-channels method is used for Coulomb and nuclear excitations of E1, E2, E3, M1, and M2 multipolarities, respectively. The program applies to an arbitrary nucleus, specified by the spins and energies of the levels and by reduced matrix elements. For given bombarding conditions, the angular distribution of elastic and inelastic scattered particles and angular distributions of gamma-rays from the excited nucleus are computed.

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arXiv2002

Breakup of the weakly bound 17F nucleus

The breakup of the radioactive 17F nucleus into a proton and 16O is studied for the reaction 17F + 208Pb --> p + 16O + 208Pb at 65 MeV/nucleon. The possibility of using this reaction as a test case for studying dynamical Coulomb reacceleration effects is assessed. It is shown that the reaction is dominated by elastic nuclear breakup (diffraction dissociation).

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arXiv2002

Effective Field Theory for Halo Nuclei: Shallow p-Wave States

Halo nuclei are a promising new arena for studies based on effective field theory (EFT). We develop an EFT for shallow p-wave states and discuss the application to elastic n-alpha scattering. In contrast to the s-wave case, both the scattering length and effective range enter at leading order. We also discuss the prospects of using EFT in the description of other halos, such as the three-body halo nucleus 6He.

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arXiv2002

Coupling of giant resonances to soft E1 and E2 modes in B-8

The dynamic coupling between giant resonance states and "soft", low-energy excitation, modes in weakly-bound nuclei is investigated. A coupled-channels calculation is reported for the reaction 8B + Pb --> p + 7Be + Pb at 83 MeV/nucleon. It is shown that the low-energy response is only marginally modified by transitions to the isovector giant dipole and isoscalar giant quadrupole resonances.

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arXiv2002

Peripheral heavy ion collisions as a probe of the nuclear gluon distribution

At high energies a quark-gluon plasma is expected to be formed in heavy ion collisions at RHIC and LHC. The theoretical description of these processes is directly associated to a complete knowledge of the details of medium effects in the nuclear gluon distribution. In this paper we analyze the possibility to constraint the behavior of this distribution considering peripheral heavy ion collisions. We reanalyze the photoproduction of heavy quarks for the deduction of the in-medium gluon distribution using three current parameterizations for this parton distribution. Moreover, we show that the elastic photoproduction of vector mesons is a potential process to probe the nuclear gluon distribution.

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