Narrow Results

We prove in this paper that the magnitude of anomaly in deuteron stripping reactions on A ≈ 80–110 mass target nuclei, at threshold of analogue channel, is proportional to the 3 - p wave neutron strength function. The result is obtained from analysis, within an empirical approach and computational frameworks, of the cross-section and analyzing power experimental data related to this (d,p) anomaly.

We report our recent numerical results of total reaction cross sections of light neutron-rich nuclei, such as carbons and oxygens, in the Glauber approximation to study the exotic structure of neutron-rich unstable nuclei.

Direct searches for dark matter lead to serious problems for simple models with stable neutral Weakly Interacting Massive Particles (WIMPs) as candidates for dark matter. A possibility is discussed that new stable quarks and charged leptons exist and are hidden from detection, being bound in neutral dark atoms of composite dark matter. Stable -2 charged particles O^-- are bound with primordial helium in O-helium (OHe) atoms, being specific nuclear interacting form of composite Warmer than Cold dark matter. Slowed down in the terrestrial matter, OHe is elusive for direct methods of underground dark matter detection based on the search for effects of nuclear recoil in WIMP-nucleus collisions. The positive results of DAMA experiments can be explained as annual modulation of radiative capture of O-helium by nuclei. In the framework of this approach, test of DAMA results in detectors with other chemical content becomes a nontrivial task, while the experimental search of stable charged particles at LHC or in cosmic rays acquires a meaning of direct test for composite dark matter scenario.

New $0^{+}$ resonance parameters have been extracted and interpreted in terms of the experimental neutron–proton branching ratio of $\mathrm{\text{d+d}}$ reactions in strontium and tantalum metallic lattices. The material-dependent cross-section formula, which includes the new $0^{+}$ resonance parameters, the screening effect, and the effective mass, have been applied to $d{(d,p)}^{3}H$ and ${}^{2}H{(d,n)}^{3}He$ reactions in metallic environments. The contributions of the $0^{+}$ resonance and effective electron mass are crucial to the understanding of the discrepancy between the theoretical and experimental screening values in metallic environments. As a different and connected part of this research, we have proposed a new target material: deuterated metal wire mesh structures. Experimentally confirmed numerical results for Pendry’s effective electron mass for aluminum metal wire have been used to calculate the cross-section and screening energy.

NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross-section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer at the INFN-LNS laboratory. However, the tiny values of DCE cross-sections and the resolution requirements demand beam intensities much higher than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities promoted by the POTLNS^a project in this perspective is intimately connected to the NUMEN project. This paper describes the solutions proposed as a result of the R&D activity performed during the recent years. The goal is to develop suitable technologies allowing for the measurements of DCE cross-section under extremely high beam intensities.

PIR01_00005 — potenziamento dell’infrastruttura di ricerca Laboratori Nazionali del Sud per la produzione di fasci di ioni ad alta intensitá.

The conditions of local Lorentz invariance (LLI) breakdown, obtained during neutron emission from a sonicated cylindrical bar of AISI 304 steel, were reproduced in a system made of a mole of mercury. After 3 min, a part of the liquid transformed into solid state material, in which isotopes were found with both higher and lower atomic mass with respect to the starting material. Changes in the atomic weight without production of gamma radiation and radionuclides are made possible by deformed space–time reactions.

Three cases are reviewed of radioactive material with anomalous decay after ultrasound irradiation. In the pure element thorium-228 in distilled water, the radioactivity decreased faster after cavitation than the natural decay. The more complex molecule of Nickel Nitrate, made of radioactive nickel-63, in solution of nitric acid and distilled water was investigated before and after ultrasound irradiation. The X-rays produced by Bremsstrahlung of the electrons from the beta decay of Ni-63 were recorded and a 13% decrease of intensity was measured after 100 s of sonication. A decrease of nickel and an increase of other elements was detected by mass spectrometry in the sonicated sample. The Cobalt-57 decay was investigated by detecting the gamma and X-ray intensity from the Iron-57 resulting after its beta emission. In this third case too, an anomalous decay was observed after sonication. These three cases of anomalous behavior can be explained at the light of the Deformed Space–Time theory. It assumes that a suitable sudden variation of energy density can induce a local deformation of space–time, thus violating the Local Lorentz Invariance. This variation can be created by the ultrasounds in the matter, thus, allowing reactions that cannot occur in a flat (Minkowskian) space–time. The “neutralization” of a radionuclide occurs when it undergoes a DST transformation changing the radionuclide into non-radioactive nuclides.

Positive results of dark matter searches in DAMA/NaI and DAMA/LIBRA experiments, being put together with the results of other groups, can imply nontrivial particle physics solutions for cosmological dark matter. Stable particles with charge -2, bound with primordial helium in O-helium "atoms" (OHe), represent a specific warmer than cold nuclear-interacting form of dark matter. Slowed down in the terrestrial matter, OHe is elusive for direct methods of underground dark matter detection used in cryogenic experiments. However the radiative capture of OHe by Na and I nuclei can lead to annual variations of energy release in the energy interval of 2–5 keV in DAMA/NaI and DAMA/LIBRA experiments.

The importance of nuclear reactions in low-density astrophysical plasmas with ion temperatures T ≥10¹⁰ K has been recognized for more than thirty years. However, the lack of comprehensive data banks of relevant nuclear reactions and the limited computational power have not previously allowed detailed theoretical studies. Recent developments in these areas make it timely to conduct comprehensive studies on the nuclear properties of very hot plasmas formed around compact relativistic objects such as black holes and neutron stars. Such studies are of great interest in the context of scientific programs of future low-energy cosmic γ-ray spectrometry. In this work, using the publicly available code TALYS, we have built a large nuclear network relevant for temperatures exceeding 10¹⁰ K. We have studied the evolution of the chemical composition and accompanying prompt gamma-ray emission of such high-temperature plasmas. We present the results on the abundances of light elements D, T, ³He, ⁴He, ⁶Li, ⁷Li, ⁹Be, ¹⁰B, ¹¹B, and briefly discuss their implications on the astrophysical abundances of these elements.

Among dark atom scenarios, the simplest and most predictive one is that of O-helium (OHe) dark atoms, in which a leptonlike doubly charged particle O^–– is bound to a primordial helium nucleus, and is the main constituent of dark matter. The OHe cosmology has several successes: it leads to a warmer-than-cold-dark matter scenario for large-scale-structure formation, it can provide an explanation for the excess in positron annihilation line in the galactic bulge and it may explain the results of direct dark matter searches. This model liberates the physics of dark atoms from many unknown features of new physics, but it is still not free from astrophysical uncertainties. It also demands a deeper understanding of the details of known nuclear and atomic physics, which are still somewhat unclear in the case of nuclear interacting “atomic” shells. These potential problems of the OHe scenario are also discussed.

This review article covers a variety of phenomena observed in heavy ion collisions in full range of available collisions energies. The main reaction channels characteristic of each energy domain are discussed in conjuction with existing nuclear reaction models. Methods used to extract characteristic features of hot nuclear objects are shown. Relations between properties of microscopic nuclear objects and infinite nuclear matter are presented. At the end of this review the transition between hadronic phase and the strongly interacting quark-gluon plasma is discussed.

This review focuses on nuclear reactions in astrophysics and, more specifically, on reactions with light ions (nucleons and α particles) proceeding via the strong interaction. It is intended to present the basic definitions essential for studies in nuclear astrophysics, to point out the differences between nuclear reactions taking place in stars and in a terrestrial laboratory, and to illustrate some of the challenges to be faced in theoretical and experimental studies of those reactions. The discussion revolves around the relevant quantities for astrophysics, which are the astrophysical reaction rates. The sensitivity of the reaction rates to the uncertainties in the prediction of various nuclear properties is explored and some guidelines for experimentalists are also provided.

In nuclear physics, the inverse scattering problem for coupled channels at fixed energies searches for the coupling potentials by using the S matrix as information. On the basis of the Newton–Sabatier method we investigate the special case that the coupling is independent of the total angular momentum. We discuss transparent potentials and consider a principal, but not practical method for the solution of coupling potentials dependent on total angular momentum.

The effect of neutron enrichment of the neck formed during reseparation of two colliding nuclei was studied with the aim to infer an information on the density dependence of the asymmetry energy term in the equation of state. By using a version of the QMD model of Łukasik it is shown that the neutrons-to-protons ratio of the intermediate mass fragments (IMF) emitted from the neck, 〈N/Z〉, is not a sufficiently sensitive observable to discriminate between different assumptions regarding the symmetry term of the equation of state. As an alternative, isotopic ratios of selected pairs of isotopes turned out to be useful observables more sensitive to the assumed form of the symmetry term of the equation of state. A comparison with experimental data on isotopic ratios for beryllium and boron IMFs from the ¹²⁴Sn + ⁶⁴Ni reaction at 35 MeV/nucleon tentatively suggests that the ASY-SOFT option of the symmetry energy term in EOS is preferred.

The collapsar scenario for long-duration gamma ray bursts (GRBs) has been proposed as a possible astrophysical site for r-process nucleosynthesis. We summarize the status of r-process nucleosynthesis calculations of our group and others in the context of a magnetohydrodynamics + neutrino-heated collapsar model. In the simulations of our group, we begin with a relativistic magnetohydrodynamic model including ray-tracing neutrino transport to describe the development of the black hole accretion disk and the neutrino heating of the funnel region above the black hole. The late-time evolution of the associated jet was then followed using axisymmetric special relativistic hydrodynamics. We utilized representative test particles to follow the temperature, entropy, electron fraction and density for material flowing within the jet from ejection from the accretion disk until several thousand kilometer above the black hole as temperatures fall from 9×10⁹ to 3×10⁸ K. The evolution of nuclear abundances from nucleons to heavy nuclei for ejected test particle trajectories has been solved in a large nuclear reaction network. It was found that an r-process-like abundance distribution forms in material ejected in the collapsar jet.

Primordial nucleosynthesis remains as one of the pillars of modern cosmology. It is the testing ground upon which many cosmological models must ultimately rest. It is our only probe of the universe during the important radiation-dominated epoch in the first few minutes of cosmic expansion. This paper reviews the basic equations of space-time, cosmology, and big bang nucleosynthesis. We also summarize the current state of observational constraints on primordial abundances along with the key nuclear reactions and their uncertainties. We summarize which nuclear measurements are most crucial during the big bang. We also review various cosmological models and their constraints. In particular, we analyze the constraints that big bang nucleosynthesis places upon the possible time variation of fundamental constants, along with constraints on the nature and origin of dark matter and dark energy, long-lived supersymmetric particles, gravity waves, and the primordial magnetic field.

Primordial nucleosynthesis, or big bang nucleosynthesis (BBN), is one of the three evidences for the big bang model, together with the expansion of the universe and the cosmic microwave background. There is a good global agreement over a range of nine orders of magnitude between abundances of ⁴He, D, ³He and ⁷Li deduced from observations, and calculated in primordial nucleosynthesis. However, there remains a yet-unexplained discrepancy of a factor $\approx 3$, between the calculated and observed lithium primordial abundances, that has not been reduced, neither by recent nuclear physics experiments, nor by new observations. The precision in deuterium observations in cosmological clouds has recently improved dramatically, so that nuclear cross-sections involved in deuterium BBN needs to be known with similar precision. We will briefly discuss nuclear aspects related to the BBN of Li and D, BBN with nonstandard neutron sources, and finally, improved sensitivity studies using a Monte Carlo method that can be used in other sites of nucleosynthesis.

An experiment in direct registration of neutron nuclei ($x\ge 6$) using a multineutron detector has been conducted for the first time. The results indicate the presence of hexaneutron and/or octaneutron emission in decay of ${}^{238}$U nuclei. The multineutron detector consisted of 20 ³He-filled counters placed in a polyethylene moderator. Samples (emitters) of uranium trioxide (UO₃) were used as sources of neutron nuclei. The experiment was conducted for a period of 112.66 days. Thus, the ratios of probabilities of hexaneutron and/or octaneutron emission by the ${}^{238}$U nuclei to the probabilities of $\alpha$-decay have been determined as upper bounds at a 90% confidence level: $\lambda {(}^{6}n)/{\lambda }_{\alpha }\le 9.3\times 10^{-9}$ and $\lambda {(}^{8}n)/{\lambda }_{\alpha }\le 3.6\times 10^{-10}$.

The production of heavy-mass elements due to the rapid neutron-capture mechanism ($r$-process) is associated with astrophysical scenarios, such as supernovae and neutron-star mergers. In the $r$-process the capture of neutrons is followed by $\beta$-decays until nuclear stability is reached. A key element in the chain of nuclear weak-decays leading to the production of isotopes may be the change of the parameters controlling the neutrino sector, due to the mixing of active and sterile species. In this work, we have addressed this question and calculated $\beta$-decay rates for the nuclei involved in the $r$-process chains as a function of the neutrino mixing parameters. These rates are then used in the calculation of the abundance of the heavy elements produced in core-collapse supernova and in neutron-star mergers, starting from different initial mass-fraction distributions. The analysis shows that the core-collapse supernova environment contributes with approximately $30\%$ of the total heavy nuclei abundance while the neutron-star merger contributes with about $70\%$ of it. Using available experimental data we have performed a statistical analysis to set limits on the active-sterile neutrino mixing angle and found a best-fit value ${sin}^{2}2{𝜃}_{14}=0.22$, a value comparable with those found in other studies reported in the literature.

Theoretical nuclear reaction codes are crucial for studying cross-section and S-factors of nuclear reactions required for the thermonuclear reaction rate calculations. We analyze two reactions ⁸Li($\alpha ,n$)¹¹B and ¹⁴N($p,\gamma$)¹⁵O, using both TALYS and EMPIRE codes. We stress that these reactions are highly important for CNO cycle but the extent of involvement of experimental datasets are meager and conflicting. For the first reaction, the trend of experimental data has been predicted satisfactorily by the codes. The reaction rate is also matched with REACLIB calculation. However, in ¹⁴N($p,\gamma$)¹⁵O, none of the codes could predict the resonant structures in the experimental data at the lower energies. The importance of our work is a sincere attempt to validate the TALYS and EMPIRE predictions for cross-section, S-factor and the reaction rate, simultaneously.