Showing papers by "Carlos A. Bertulani published in 2017"
TL;DR: The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in ^{48}Ca of 0.14-0.20 fm.
Abstract: The electric dipole strength distribution in ^{48}Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability α_{D}(^{48}Ca)=2.07(22) fm^{3}. Remarkably, the dipole response of ^{48}Ca is found to be very similar to that of ^{40}Ca, consistent with a small neutron skin in ^{48}Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in ^{48}Ca of 0.14-0.20 fm.
149 citations
TL;DR: In this paper, it was shown that the BBN theory overestimates the primordial 7Li abundance by about a factor of three, which is the so-called "so-called Big Bang nucleosynthesis" problem.
Abstract: Big Bang nucleosynthesis (BBN) theory predicts the abundances of the light elements D, 3He, 4He, and 7Li produced in the early universe. The primordial abundances of D and 4He inferred from observational data are in good agreement with predictions, however, BBN theory overestimates the primordial 7Li abundance by about a factor of three. This is the so-called
68 citations
TL;DR: The sensitivity of the total neutron-removal cross section is high enough so that the required accuracy can be reached experimentally with the recent developments of new detection techniques, and the slope parameter L of the symmetry energy could be constrained down to ±10 MeV by such a measurement, with a 2% accuracy.
Abstract: An experimentally constrained equation of state of neutron-rich matter is fundamental for the physics of nuclei and the astrophysics of neutron stars, mergers, core-collapse supernova explosions, and the synthesis of heavy elements. To this end, we investigate the potential of constraining the density dependence of the symmetry energy close to saturation density through measurements of neutron-removal cross sections in high-energy nuclear collisions of 0.4 to 1 GeV/nucleon. We show that the sensitivity of the total neutron-removal cross section is high enough so that the required accuracy can be reached experimentally with the recent developments of new detection techniques. We quantify two crucial points to minimize the model dependence of the approach and to reach the required accuracy: the contribution to the cross section from inelastic scattering has to be measured separately in order to allow a direct comparison of experimental cross sections to theoretical cross sections based on density functional theory and eikonal theory. The accuracy of the reaction model should be investigated and quantified by the energy and target dependence of various nucleon-removal cross sections. Our calculations explore the dependence of neutron-removal cross sections on the neutron skin of medium-heavy neutron-rich nuclei, and we demonstrate that the slope parameter L of the symmetry energy could be constrained down to ±10 MeV by such a measurement, with a 2% accuracy of the measured and calculated cross sections.
40 citations
TL;DR: The present results validate the Brink-Axel hypothesis for ^{96}Mo and provide independent confirmation of the methods used to separate gamma strength function and level density in γ decay experiments.
Abstract: The gamma strength function and level density of ${1}^{\ensuremath{-}}$ states in $^{96}\mathrm{Mo}$ have been extracted from a high-resolution study of the ($\stackrel{\ensuremath{\rightarrow}}{p}$, ${\stackrel{\ensuremath{\rightarrow}}{p}}^{\ensuremath{'}}$) reaction at 295 MeV and extreme forward angles. By comparison with compound nucleus $\ensuremath{\gamma}$ decay experiments, this allows a test of the generalized Brink-Axel hypothesis in the energy region of the pygmy dipole resonance. The Brink-Axel hypothesis is commonly assumed in astrophysical reaction network calculations and states that the gamma strength function in nuclei is independent of the structure of the initial and final state. The present results validate the Brink-Axel hypothesis for $^{96}\mathrm{Mo}$ and provide independent confirmation of the methods used to separate gamma strength function and level density in $\ensuremath{\gamma}$ decay experiments.
37 citations
TL;DR: In this article, the authors determined the cross section of the (n, α) reaction by using Trojan Horse experimental data for the 7Li(p, α)-4He reaction and correcting for Coulomb effects.
Abstract: 7Be destruction channels are currently a matter of study because of their influence on the 7Li cosmological abundances. Here, we determine the cross section of the (n, α) reaction by using Trojan Horse experimental data for the 7Li(p, α)4He reaction and correcting for Coulomb effects. The deduced 7Be(n, α)4He data overlap with the Big Bang nucleosynthesis energies and the deduced reaction rate allows us to evaluate the corresponding cosmological implications.
36 citations
TL;DR: In this article, the authors discussed the relationship between the resonance width and the asymptotic normalization coefficient (ANC) with the observable reduced width, when the sub-threshold bound state is the only channel or coupled with an open channel, which is a resonance.
Abstract: In this paper we discuss the $R$-matrix approach to treat the subthreshold resonances for the single-level and one-channel and for the single-level and two-channel cases In particular, the expression relating the asymptotic normalization coefficient (ANC) with the observable reduced width, when the subthreshold bound state is the only channel or coupled with an open channel, which is a resonance, is formulated Since the ANC plays a very important role in nuclear astrophysics, these relations significantly enhance the power of the derived equations We present the relationship between the resonance width and the ANC for the general case and consider two limiting cases: wide and narrow resonances Different equations for the astrophysical $S$ factors in the $R$-matrix approach are presented After that we discuss the Trojan horse method (THM) formalism The developed equations are obtained using the surface-integral formalism and the generalized $R$-matrix approach for the three-body resonant reactions It is shown how the Trojan horse (TH) double-differential cross section can be expressed in terms of the on-the-energy-shell astrophysical $S$ factor for the binary subreaction Finally, we demonstrate how the THM can be used to calculate the astrophysical $S$ factor for the neutron generator $^{13}\mathrm{C}(\ensuremath{\alpha},\phantom{\rule{016em}{0ex}}n)^{16}\mathrm{O}$ in low-mass AGB stars At astrophysically relevant energies this astrophysical $S$ factor is controlled by the threshold level $1/{2}^{+},{E}_{x}=6356$ keV Here, we reanalyzed recent TH data taking into account more accurately the three-body effects and using both assumptions that the threshold level is a subthreshold bound state or it is a resonance state
16 citations
Technische Universität Darmstadt1, TRIUMF2, University of Santiago de Compostela3, Lund University4, Michigan State University5, Helmholtz-Zentrum Dresden-Rossendorf6, Spanish National Research Council7, University of Vigo8, University of Surrey9, University of Liverpool10, Kurchatov Institute11, GSI Helmholtz Centre for Heavy Ion Research12, University of Lisbon13, Saha Institute of Nuclear Physics14, University of Giessen15, ATOMKI16, University of Edinburgh17, Complutense University of Madrid18, University of Birmingham19, Technische Universität München20, Goethe University Frankfurt21, Chalmers University of Technology22, Max Planck Society23
TL;DR: In this article, the authors studied the energy and width of the J(pi) = 3(1)(+) unbound state in F-26 and F-25, respectively.
Abstract: Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The F-26 nucleus, composed of a deeply bound pi 0d(5/2) proton and an unbound v0d(3/2) neutron on top of an O-24 core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a J(pi) = 1(1)(+) - 4(1)(+) multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The J(pi) = 1(1)(+), 2(1)(+), 4(1)(+) bound states have been determined, and only a clear identification of the J(pi) = 3(1)(+) is missing. Purpose: We wish to complete the study of the J(pi) = 1(1)(+) - 4(1)(+) multiplet in F-26, by studying the energy and width of the J(pi) = 3(1)(+) unbound state. The method was first validated by the study of unbound states in F-25, for which resonances were already observed in a previous experiment. Method: Radioactive beams of Ne-26 and Ne-27, produced at about 440AMeV by the fragment separator at the GSI facility were used to populate unbound states in F-25 and F-26 via one-proton knockout reactions on a CH2 target, located at the object focal point of the (RB)-B-3/LAND setup. The detection of emitted. rays and neutrons, added to the reconstruction of the momentum vector of the A - 1 nuclei, allowed the determination of the energy of three unbound states in F-25 and two in F-26. Results: Based on its width and decay properties, the first unbound state in F-25, at the relative energy of 49(9) keV, is proposed to be a J(pi) = 1/ 2(-) arising from a p1/2 proton- hole state. In F-26, the first resonance at 323(33) keV is proposed to be the J(pi) = 3(1)(+) member of the J(pi) = 1(1)(+) - 4(1)(+) multiplet. Energies of observed states in F-25,F-26 have been compared to calculations using the independent-particle shell model, a phenomenological shell model, and the ab initio valence-space in-medium similarity renormalization group method. Conclusions: The deduced effective proton- neutron interaction is weakened by about 30-40% in comparison to the models, pointing to the need for implementing the role of the continuum in theoretical descriptions or to a wrong determination of the atomic mass of F-26.
15 citations
University of Santiago de Compostela1, Texas A&M University2, Universidad Santo Tomás3, Michigan State University4, GSI Helmholtz Centre for Heavy Ion Research5, Technische Universität Darmstadt6, University of Vigo7, Chalmers University of Technology8, Central Michigan University9, Saint Mary's University10, Niigata University11
TL;DR: In this paper, the production cross sections of residual nuclei obtained by knockout and fragmentation reactions of different tin isotopes accelerated at 1A GeV have been measured with the fragment separator (FRS) at GSI, Darmstadt.
Abstract: Production cross sections of residual nuclei obtained by knockout and fragmentation reactions of different tin isotopes accelerated at 1A GeV have been measured with the fragment separator (FRS) at GSI, Darmstadt. The new measurements are used to investigate the neutron-excess dependence of the neutron- and proton-knockout cross sections. These cross sections are compared toGlauber model calculations coupled to a nuclear de-excitation code in order to investigate the role of the remnant excitations. This bench marking shows an overestimation of the cross sections for the removal of deeply bound nucleons. A phenomenological increase in the excitation energy induced in the remnants produced in these cases allows us to reproduce the measured cross sections.
12 citations
Technische Universität Darmstadt1, GSI Helmholtz Centre for Heavy Ion Research2, University of Groningen3, University of Santiago de Compostela4, Goethe University Frankfurt5, University of Birmingham6, Michigan State University7, Helmholtz-Zentrum Dresden-Rossendorf8, Texas A&M University9, Spanish National Research Council10, University of Vigo11, University of Surrey12, Saha Institute of Nuclear Physics13, University of Liverpool14, Kurchatov Institute15, University of Lisbon16, Saint Mary's University17, Complutense University of Madrid18, Aarhus University19, Technische Universität München20, Chalmers University of Technology21, Daresbury Laboratory22, University of Cologne23, University of Notre Dame24, University of Edinburgh25
TL;DR: In this paper, the authors measured exclusive relative energy spectra of the Coulomb dissociation at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of $^{17}$C into the ground state of
Abstract: With the R$^{3}$B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of $^{18}$C at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of $^{17}$C into the ground state of $^{18}$C. Those data have been used to constrain theoretical calculations for transitions populating excited states in $^{18}$C. This allowed to derive the astrophysical cross section $\sigma^{*}_{\mathrm{n}\gamma}$ accounting for the thermal population of $^{17}$C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures $T_{9}\leq{}1$~GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of $^{17}$C on the production of second- and third-peak elements in contrast to earlier sensitivity studies.
12 citations
TL;DR: In this article, the authors developed a treatable model to include deformed wave functions and a dynamical knockout formalism that includes the dependence on the nuclear orientation to study the neutron removal from $ √ √ n−1 n−3 n−2 n−4 n−5 n−6 n−7 n−8 n−10 n−11 n−12 n−13 n−14 n−15 n−16 n−17 n−18 n−19 n−20 n−21 n−23 n−24 n−28 n−30
Abstract: Experimental data on Coulomb breakup and neutron removal indicate that $^{31}\mathrm{Ne}$ is one of the heaviest halo nuclei discovered so far. The possible ground state of $^{31}\mathrm{Ne}$ is either $3/{2}^{\ensuremath{-}}$ coming from the $p$-wave halo or $1/{2}^{+}$ coming from the $s$-wave halo. In this work, we develop a treatable model to include deformed wave functions and a dynamical knockout formalism that includes the dependence on the nuclear orientation to study the neutron removal from $^{31}\mathrm{Ne}$ projectiles at energies around $E\ensuremath{\approx}200$ MeV/nucleon. A detailed account of the effects of deformation on cross sections and longitudinal momentum distributions is made. Our numerical analysis indicates a preference for the $^{31}\mathrm{Ne}$ ground state with spin-parity $3/{2}^{\ensuremath{-}}$.
10 citations
TL;DR: By using the $R$-matrix approach, the authors calculated the radiative width for a resonance decaying to a bound state through electric-dipole $E1$ transitions.
Abstract: By using the $R$-matrix approach we calculate the radiative width for a resonance decaying to a bound state through electric-dipole $E1$ transitions The total radiative width is determined by the interference of the nuclear internal and external radiative width amplitudes For a given channel radius the external radiative width amplitude is model independent and is determined by the asymptotic normalization coefficient (ANC) of the bound state to which the resonance decays It also depends on the partial resonance width To calculate the internal radiative width amplitude we show that a single-particle-potential model is appropriate We compare our results with a few experimental data
TL;DR: In this paper, the momentum distribution of 11Be fragments produced by the breakup of 12Be interacting with a proton target at 700.5 MeV/u energy has been measured at GSI Darmstadt.
TL;DR: In this article, the authors proposed that Rydberg nuclear molecules, which represent the exotic, halo nuclei version, such as Be 11 + 11 Be, of the well known quasimolecules observed in stable nuclei such as C 12 + 12 C, might be common structures that could manifest their existence along the dripline.
TL;DR: In this article, the authors explore the possibility that the electron screening puzzle is due to nuclear clusterization and polarization in the fusion reactions, and discuss the supporting arguments for this scenario.
Abstract: Electron screening changes appreciably the magnitude of astrophysical nuclear reactions within stars This effect is also observed in laboratory experiments on Earth, where atomic electrons are present in the nuclear targets Theoretical models were developed over the past 30 years and experimental measurements have been carried out to study electron screening in thermonuclear reactions None of the theoretical models were able to explain the high values of the experimentally determined screening potentials We explore the possibility that the “electron screening puzzle” is due to nuclear clusterization and polarization e_ects in the fusion reactions We will discuss the supporting arguments for this scenario
TL;DR: In this paper, the role of relativistic corrections in heavy-ion Coulomb scattering at intermediate energies was investigated by numerically solving a full set of coupled equations, and two methods were compared: an exact account of interaction retardation and a method based on the expansion of effective Lagrangians in powers of the ion velocities, $v/c).
Abstract: The role of relativistic corrections in heavy-ion Coulomb scattering at intermediate energies (${E}_{\text{lab}}\ensuremath{\gtrsim}50$ MeV/nucleon) is investigated by numerically solving a full set of coupled equations. We compare two methods: (a) one involving an exact account of interaction retardation and (b) a method based on the expansion of effective Lagrangians in powers of the ion velocities, $v/c$. Our study makes it possible to infer the relevance of kinematic corrections, retardation, and magnetic interactions such as the Darwin force. We show that analytical formulas are able to describe all aspects of experimental interest in relativistic effects in heavy-ion Coulomb scattering at intermediate energies without having to solve numerically the coupled equations.
TL;DR: Theoretical models were developed over the past 30 years and experimental measurements have been carried out to study electron screening in thermonuclear reactions as discussed by the authors, but none of the theoretical models were able to explain the high values of the experimentally determined screening potentials.
Abstract: Electron screening changes appreciably the magnitude of astrophysical nuclear reactions within stars. This effect is also observed in laboratory experiments on Earth, where atomic electrons are present in the nuclear targets. Theoretical models were developed over the past 30 years and experimental measurements have been carried out to study electron screening in thermonuclear reactions. None of the theoretical models were able to explain the high values of the experimentally determined screening potentials. We explore the possibility that the "electron screening puzzle" is due to nuclear clusterization and polarization effects in the fusion reactions. We will discuss the supporting arguments for this scenario.
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TL;DR: In this paper, the authors extend previous studies of big bang nucleosynthesis, with the assumption that ordinary matter and dark matter sectors are entangled through the number of degrees of freedom entering the Friedmann equations.
Abstract: We extend previous studies of big bang nucleosynthesis, with the assumption that ordinary matter and dark matter sectors are entangled through the number of degrees of freedom entering the Friedmann equations. This conjecture allows us to find a relation between the temperatures of the weakly interacting matter and dark-matter sectors. The constraints imposed by observations are studied by comparison with calculations of big bang nucleosynthesis for the abundance of light elements. It is found that these constraints are compatible with cold dark matter and a wide range number of dark sectors.
TL;DR: In this paper, exotic charmonium production in γγ interactions in heavy ion collisions is discussed and predictions for the production cross section of several of these states in ultra-peripheral collisions of proton-proton and nucleus-nucleus beams at the CERN Large Hadron Collider energies.
Abstract: We discuss exotic charmonium production in γγ interactions in heavy ion collisions and present predictions for the production cross section of several of these states in ultra-peripheral collisions of proton-proton and nucleus-nucleus beams at the CERN Large Hadron Collider energies. Our results demonstrate that the experimental study of these processes is feasible and can be used to put limits on the theoretical decay widths and yield valuable information about the structure of multiquark states.
30 Jun 2017
TL;DR: In this paper, the authors make a short review of recent progress on topics of current interest in nuclear physics and nuclear astrophysics and present a test case based on applications of such potentials to phase-shift analysis.
Abstract: In this contribution we make a short review of recent progress on topics of current interest in nuclear physics and nuclear astrophysics. In particular, we discuss a re-analysis of the extraction of the dipole response of the pigmy resonance in 68Ni based on a continuum discretized coupled-channels calculation in relativistic Coulomb excitation experiments. We also discuss the forthcoming progresses made by our group on the Alt-Sandhas-Grassberber approach to (d,p) reactions and future expectations. The role of separable potentials in solving such equations with a test case based on applications of such potentials to phase-shift analysis is also presented.