Using the Monte Carlo simulation method accompanied by the modifying effects of the density distributions overlapping, we have examined the nuclear matter incompressibility effects for asymmetric systems with light nuclei, namely $^{16}$O+$^{27}$Al and $^{16}$O+$^{28}$Si fusion reactions. The obtained results show that the nuclear equation of state has considerable influence on the calculation of fusion probabilities for these asymmetric systems.
Existing data on near-barrier fusion excitation functions of medium and heavy nucleus-nucleus systems have been analyzed using a simple diffused barrier formula derived assuming the Gaussian shape of the barrier height distributions. Fusion cross section is obtained by folding the Gaussian barrier distribution with the classical expression for the fusion cross section for a fixed barrier. The energy dependence of the fusion cross section, thus obtained, provides good description to the existing data on near-barrier fusion and capture excitation functions for medium and heavy nucleus-nucleus sy…
It is suggested that the full nucleus-nucleus potential consists of the macroscopic and shell-correction parts. The deep sub-barrier fusion hindrance takes place in a nucleus-nucleus system with a strong negative shell-correction contribution to the full heavy-ion potential, while a strong positive shell-correction contribution to the full potential leads to weak enhancement of the deep sub-barrier fusion cross section.
The dynamical nucleus-nucleus potentials for fusion reactions 40Ca+40Ca, 48Ca+208Pb and 126Sn+130Te are studied with the improved quantum molecular dynamics (ImQMD) model together with the extended Thomas-Fermi approximation for the kinetic energies of nuclei. The obtained fusion barrier for 40Ca+40Ca is in good agreement with the extracted fusion barrier from the measured fusion excitation function, and the depth of the fusion pockets are close to the results of time-dependent Hartree-Fock calculations. The energy dependence of fusion barrier is also investigated. For heavy fusion system, the…
The nucleus-nucleus potential and energy dissipation in fusion reactions are obtained from microscopic mean-field dynamics. The deduced potentials nicely reproduce the one extracted from experimental data. Energy dissipation shows a universal behaviour between different reactions. Also, the dispersion of mass distribution in transfer reaction is investigated in a stochastic mean-field dynamics. By including initial fluctuations in collective space, the description of the dispersion is much improved compared to that of mean field only. The result is consistent with the macroscopic phenomenologi…
Adiabatic fusion potentials, extended well into compound nucleus region, are calculated for a number of reactions within the static Hartree-Fock method with the Skyrme SkM* interaction. The calculated fusion barriers agree quite well with the data, in spite of considerable errors in reaction Q values. This suggests some error cancellation, possibly with the relative kinetic energy term. Calculated berrier heights are consistent with the idea of fusion hindrance in tip collisions. Adiabatic potentials differ considerably from the results of the frozen density approximation. We briefly discuss r…
This paper presents reaction cross section predictions. These predictions are the result of a continuous pipeline which originates from a microscopic nuclear interaction. Density parameters and effective nucleon-nucleon cross sections (both involved in the reaction calculations) are by-products of the same equation of state. First, we perform tests of sensitivity to medium effects using reactions involving 208-Pb, a stable but weakly isospin-asymmetric nucleus. We also show predictions for collisions of some neutron-rich isotopes of Calcium and Argon. We observe significant sensitivity of the …
To explain the experimental facts that the fusion cross sections of proton-halo nucleus on heavy target nucleus is not enhanced as expected, the shielding supposition has been proposed. Namely, the proton-halo nucleus is polarized with the valence proton being shielded by the core. In this paper, within the frame of the Improved Quantum Molecular Dynamics model, the fusion reactions by $^{17}$F on $^{208}$Pb around Coulomb barrier have been simulated. The existence of shielding effect is verified by microscopic dynamics analysis and its influence on the effective interaction potential is also …
We study the scaling properties of proton-nucleus total reaction cross sections for stable nuclei and propose an approximate expression in proportion to Z^{2/3}σ_{pp}^{total} + N^{2/3} σ_{pn}^{total}. Based on this expression, we can derive a relation that enables us to predict a total reaction cross section for any stable nucleus within 10% uncertainty at most, using the empirical value of the total reaction cross section of a given nucleus.
Dynamics of the neck degree of freedom during fusioning process between heavy ions is studied. Time scales of the three degrees of freedom (the relative distance, the neck and the mass-asymmetry) are studied, showing an early equilibration of the neck. This means that a di-nucleus formed by the incident combination of ions quickly forms a mono-nucleus with a superdeformation during the fusion process and that the other two degrees of freedom have to be solved in a coupled way. A brief introduction of Langevin approach and dissipation-fluctuation dynamics is also given and of the application to…
The coherent $η$ meson energy $E_η$ distribution spectra in the proton nucleus reaction have been calculated to investigate the $π^0 - η$ mesons' interference, in addition to the study of resonance $N^*$ dynamics in the nucleus. The elementary reaction occurring in the nucleus is assumed to proceed as $ pN \to pN^* $; $ N^* \to Nη$. Born terms in the intermediate state is also considered. In a scalar-isovector nucleus, this reaction occurs because of $π^0$ and $η$ meson exchange interactions for the forward going proton and $η$ meson; other meson exchange potentials do not contribute in this p…
The understanding of the fusion probability is of particular importance to reveal the mechanism of producing superheavy elements. We present a microscopic study of the compound nucleus formation by combining time-dependent density functional theory, coupled-channels approach, and dynamical diffusion models. The fusion probability and compound nucleus formation cross sections for cold-fusion reactions $^{48}$Ca+$^{208}$Pb, $^{50}$Ti+$^{208}$Pb, and $^{54}$Cr+$^{208}$Pb are investigated and it is found that the deduced capture barriers, capture cross sections for these reactions are consistent w…
In this work we study the charge-exchange reaction to Isobaric Analog State using two types of transition densities. We show that for projectiles that do not probe the interior of the nucleus but mostly the surface of this nucleus, distinct differences in the cross-section arise when the two types of transition densities are employed. We demonstrate this by considering the (3He,t) reaction.
The set of parameters for alpha-nucleus potential is derived by using the data for both the alpha-decay half-lives and the fusion cross-sections around the barrier for reactions alpha+40Ca, alpha+59Co, alpha+208Pb. The alpha-decay half-lives are obtained in the framework of a cluster model using the WKB approximation. The evaluated alpha-decay half-lives and the fusion cross-sections agreed well with the data. Fusion reactions between alpha-particle and heavy nuclei can be used for both the formation of very heavy nuclei and spectroscopic studies of the formed compound nuclei.
A new model that includes the time-dependent dynamics of the single-particle (s.p.) motion in conjunction with the macroscopic evolution of the system is proposed for describing the compound nucleus (CN) formation in fusion of heavy nuclei. The diabaticity initially keeps the entrance system around its contact configuration, but the gradual transition from the diabatic to the adiabatic potential energy surface (PES) leads to fusion or quasifission. Direct measurements of the probability for CN formation are crucial to discriminate between the current models.
A recent article (D.A. Brown, et al., Phys. Rev. C98 024616 (2018)) rproposed a modification of the cross section formula used in practical calculations of compound nucleus reactions. We discuss the main concepts and approximations of statistical reaction theory and conclude that the standard practical implementations of the cross section formula remain the preferred choice.
A new integral formula, which has not been compiled in any integral tables or mathematical softwares, is proposed to obtain the analytical energy-angular spectra of the particles that are sequentially emitted from the discrete energy levels of the residual nuclei in the statistical theory of light nucleus reaction (STLN). In the cases of the neutron induced light nucleus reactions, the demonstration of the kinetic energy conservation in the sequential emission processes becomes straightforward thanks to this new integral formula and it is also helpful to largely reduce the volume of file-6 in …
Using the Glauber theory, we calculate reaction cross sections for the deformed halo nucleus $^{31}$Ne. To this end, we assume that the $^{31}$Ne nucleus takes the $^{30}$Ne + $n$ structure. In order to take into account the rotational excitation of the core nucleus $^{30}$Ne, we employ the particle-rotor model (PRM). We compare the results to those in the adiabatic limit of PRM, that is, the Nilsson model, and show that the Nilsson model works reasonably well for the reaction cross sections of $^{31}$Ne. We also investigate the dependence of the reaction cross sections on the ground state pro…
Reaction cross-sections are calculated using the Coulomb modified Glauber model for deformed target nuclei. The deformed nuclear matter density of the target is expanded into multipoles of order k = 0,2,4.The reaction cross-sections between some spherical and deformed nuclei are studied at energy range (10-1000 MeV/nucleon). The most significant effects in the intermediate energy range are the Coulomb field and in-medium effect that modified the trajectory of the incident beams. Introducing the deformation effect beside the Coulomb field and in-medium effect improves the agreement with the exp…
Reliable estimates of neutrino-nucleus reactions in the resonance-excitation region play an important role in many of the on-going and planned neutrino oscillation experiments. We study here neutrino-nucleus reactions in the delta-particle excitation region with the use of neutrino pion-production amplitudes calculated in a formalism in which the resonance contributions and the background amplitudes are treated on the same footing. Our approach leads to the neutrino-nucleus reaction cross sections that are significantly different from those obtained in the conventional approach wherein only th…
We systematically analyze nuclear reaction data that are sensitive to nuclear size, namely, proton-nucleus total reaction cross sections and differential elastic cross sections, using a phenomenological black-sphere approximation of nuclei that we are developing. In this framework, the radius of the black sphere is found to be a useful length scale that simultaneously accounts for the observed proton-nucleus total reaction cross section and first diffraction peak in the proton elastic differential cross section. This framework is expected to be applicable to any kind of projectile that is stro…
We reanalyse the production of $p\bar{p}$ pairs in proton-nucleus and nucleus-nucleus collisions employing novel elementary cross sections for baryon-baryon and pion-baryon production channels based on a boson-exchange model. In contrast to previous transport studies performed in the literature the secondary pion induced channel is found to be most important in both p+A and A+A collisions at subthreshold energies. A detailed comparison with the experimental data available indicates that sizeable attractive $\bar{p}$ potentials in the order of - 100 to - 150 MeV at normal nuclear matter density…
Total reaction cross sections are predicted for proton scattering from various nuclei. A simple functional form has been used that reproduces the total reaction cross sections for the scattering of protons from (15) nuclei spanning the mass range from ${}^9$Be to ${}^{238}$U and for proton energies 10 to 300 MeV.
A simple functional form has been found that gives a good representation of the total reaction cross sections for the scattering of protons from (15) nuclei spanning the mass range ${}^{9}$Be to ${}^{238}$U and for proton energies ranging from 20 to 300 MeV.
We have constructed an empirical formulae for the fusion and interaction barriers using experimental values available till date. The fusion barriers so obtained have been compared with different model predictions based on the proximity, Woods-Saxon and double folding potentials along with several empirical formulas, time dependent Hartree-Fock theories, and the experimental results. The comparison allows us to find the best model, which is nothing but the present empirical formula only. Most remarkably, the fusion barrier and radius show excellent consonance with the experimental findings for …
In order to clear up the sensitivity of the nucleus--nucleus reaction cross sections $σ_R$ to the nuclear matter distributions in exotic halo nuclei, we have calculated the values of $σ_R$ for scattering of $^6$He, $^{11}$Li, and $^{19}$C nuclei on several nuclear targets at the energy of 0.8 GeV/nucleon. The calculations were performed in the "rigid target" approximation to the Glauber theory, different shapes of the nuclear density distributions in $^6$He, $^{11}$Li, and $^{19}$C being assumed.
The formalism describing (anti)neutrino-nucleus reaction cross-sections in neutral- and charged-current processes is improved. Compact formulae for the single-particle transition matrix elements, based on the multipole expansion treatment of the relevant hadronic currents and the use of harmonic oscillator basis, are presented. As an application, the nucleus $^{127}I$, a promising target for detection of solar- and supernova-neutrinos as well as of cold dark matter candidates, is considered. Our matrix elements refer to exclusive processes of the charge-changing $^{127}I(ν_l,l^-)^{127}Xe^{\sta…
The cross sections for producing K$^-$ mesons in nucleon-hyperon elementary processes are estimated assuming one-pion exchange and using the experimentally known pion-hyperon cross sections. The results are implemented in a transport model which is applied to calculation of proton-nucleus collisions. In significant difference to earlier estimates for heavy-ion collisions the inclusion of the nucleon-hyperon cross section roughly doubles the K$^-$ production in near-threshold proton-nucleus collisions.
We apply the ``zone of reactions'' as a tool in studying the interacting system formed in a collision of relativistic nuclei. With the use of the intensity of collisions of particles (the number of collisions in unit volume per unit time), we study the space-time structure of a fireball. In this approach, three basic regions for the evolution of a system are separated by the scale of the intensity of collisions: the zone of a hot fireball, the zone of a cold fireball, and the zone of residual interaction. It is shown that the conception of a zone of reactions can be used for the determination …
Basing on the thickness (profile) function, previously obtained for the realistic Fermi type distribution of nucleons in nuclei, calculations are made of the microscopic eikonal phases of the nucleus-nucleus scattering and the total reaction cross- sections. In so doing, the phase is deduced to the one-dimensional integral provided that the Gaussian density distribution for the projectile nucleus and an arbitrary shape of the thickness density for the target nucleus are used. The problems of obtaining parameters of the "point" nucleon density are considered. A possibility of approximating the …
Neutron total reaction cross sections at 45, 50, 55, 60, 65, and 75 MeV from nuclei 12C, 28Si, 56Fe, 90Zr, and 208Pb have been measured and are compared with (microscopic) optical model predictions. The optical potentials were obtained in coordinate space by full folding effective nucleon-nucleon interactions with realistic nuclear ground state density matrices. Good to excellent agreement is found.
Nucleon total reaction and neutron total cross sections to 300 MeV for 12C and 208Pb, and for 65 MeV spanning the mass range, are predicted using coordinate space optical potentials formed by full folding of effective nucleon-nucleon interactions with realistic nuclear ground state densities. Good to excellent agreement is found with existing data.
We study a production of Coulomb-assisted $Σ^-$-nucleus bound states by nuclear ($K^-$, $π^+$) reactions within a distorted-wave impulse approximation, so as to examine several types of the $Σ$-nucleus potentials that are consistent with the available $Σ^-$ atomic X-ray data and nuclear ($π^-$, $K^+$) data. We theoretically demonstrate the inclusive ($K^-$, $π^+$) spectra of the $Σ^-$ unstable bound states on $^{28}$Si, $^{58}$Ni, and $^{208}$Pb targets at incident $K^-$ lab momenta $p_{K}= 400\text{--}800$ MeV/c. The results show that the near-recoilless ($K^-$, $π^+$) reaction on the $^{58}$…
A microscopic calculation of cross sections for fusion of oxygen isotopes $^{16}$O, $^{22}$O and $^{24}$O is presented. Fermionic Molecular Dynamics wave functions are used to describe the fully antisymmetrized and angular momentum projected nucleus-nucleus system. The same effective nucleon-nucleon interaction is used to determine the ground state properties of the nuclei as well as the nucleus-nucleus interaction. From the microscopic many-body wave function the corresponding wave function for the relative motion of two point-like nuclei is derived by a method proposed by Friedrich which lea…
The role played by nucleon-nucleon short-range correlations in photon- and electron-nucleus reactions is analyzed with a model which includes all the diagrams containing a single correlation function. The excitation of low-lying high-spin states, the reactions (e,e'), (e,e'N) and ($γ$,N) and the two-proton emission by both electrons and real photons are investigated. The results obtained for doubly-closed shell nuclei show that ($γ$,pp) appears to be the most adequate process to identify short-range correlations in the clearer way.
The strong coupling of rho meson to the nucleon produces $s$ and $p$ wave rho meson nucleon $(ρN)$ resonances. In a nucleus, the $ρN$ resonance-hole polarization generates the optical potential or self-energy for the rho meson. The scattering of rho meson due to this potential provides valuable informations about the $ρN$ resonance dynamics in a nucleus. To investigate it, we use this potential to calculate the mass distribution spectrum for the $ρ$ meson produced coherently in the proton nucleus reaction. The cross sections arising due to $s$ and $p$ wave $ρN$ resonances have been presented. …
Effetive field theory is believed to provide a useful framework for describing low-energy nuclear phenomena in a model-independent fashion. I give here a brief account of the basic features of this approach, some of its latest developments, and examples of actual calculations carried out in this framework.
The role of the nucleon recoil corrections in low--energy meson--nucleus interactions is examined. We demonstrate explicitly when calculations within the static approximation are justified and when the recoil terms need to be kept explictly in the propagators, depending on whether the S-wave two--nucleon intermediate state is Pauli blocked or not, while the meson is in flight. While the effect is studied in detail for $πd$ scattering only, a large class of other reactions is discussed for which the findings are relevant as well.
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).
Within a dynamical transport approach we investigate charged current interactions in neutrino-nucleus reactions for neutrino energies of 0.3 - 1.5 GeV with particular emphasis on resonant pion production channels via the $Δ_{33}(1232)$ resonance. The final-state-interactions of the resonance as well as of the emitted pions are calculated explicitly for $^{12}C$ and $^{56}Fe$ nuclei and show a dominance of pion suppression at moderate momenta $p_π>$ 0.2 GeV/c. A comparison to integrated $π^+$ spectra for $ν_μ+ ^{12}C$ reactions with the available (preliminary) data demonstrates a reasonable agr…
We present a detailed study of charged-current (CC) neutrino-nucleus reactions in a fully relativis- tic framework and comparisons with recent experiments spanning an energy range from hundreds of MeV up to 100 GeV within the SuperScaling Approach, which is based on the analysis of electron- nucleus scattering data and has been recently improved with the inclusion of Relativistic Mean Field theory effects. We also evaluate and discuss the impact of two-particle two-hole meson-exchange currents (2p-2h MEC) on neutrino-nucleus interactions through the analysis of two-particle two-hole axial and …
We discuss quantum effects in the diffusion process which is used to describe the shape evolution from the touching configuration of fusing two nuclei to a compound nucleus. Applying the theory with quantum effects to the case where the potential field, the mass and friction parameters are adapted to realistic values of heavy-ion collisions, we show that the quantum effects play significant roles at low temperatures which are relevant to the synthesis of superheavy elements.
We apply a statistical-evaporation model (HIVAP) to calculate the cross sections of superheavy elements, mainly about actinide targets and compare with some available experimental data. A reaction channel $^{30}$Si + $^{243}$Am is proposed for the synthesis of the element Z = 109 and the cross section is estimated.
Within the framework of the dinuclear system (DNS) model, the fusion reactions leading to the compound nuclei 274Hs and 286Cn are investigated. The fusion probability as a function of DNS excitation energy is studied. The calculated results are in good agreement with the available experimental data. The obtained results show that the fusion probabilities are obviously enhanced for the reactions located at high place in potential energy surface, although these reactions may have small values of mass asymmetry. It is found that the enhancement is due to the large potential energy of the initial …
A statistical theory of light nucleus reaction (STLN) is proposed to describe both neutron and light charged particle induced nuclear reactions with 1p-shell light nuclei involved. The dynamic of STLN is described by the unified Hauser-Feshbach and exciton model, of which the angular momentum and parity conservations are considered in equilibrium and pre-equilibrium processes. The Coulomb barriers of the incident and outgoing charged particles, which seriously influence the open reaction channels, could be reasonably considered in the incident channel and the different outgoing channels. In ki…
Total reaction cross sections of deuteron, $σ_d^{\rm R}$, are calculated by a microscopic three-body reaction model. The reaction model has no free adjustable parameter and applicable to reactions at various deuteron incident energies $E_d$ and with both stable and unstable nuclei. The predicted $σ_d^{\rm R}$ are consistent with those evaluated by a phenomenological optical potential for $E_d\leq 200$ MeV in which the potential has been parametrized. A simple formula of $σ_d^{\rm R}$ up to $E_d=1$ GeV, as a function of $E_d$, the target mass number $A$ and its atomic number $Z$, is given.
In this theoretical study, we establish an interrelationship between the nucleon-nucleon interaction potential and the nuclear fusion reaction cross-sections at low energies. The axially deformed self-consistent relativistic mean field with non-linear NL3$^*$ force is used to calculate the density distribution of the projectile and target nuclei for fusion. The Wong formula is used to estimate the fusion cross-section and barrier distribution from the nucleus-nucleus optical potential for Ni-based systems, which are known for fusion hindrance phenomena. The results of the application of the so…
Calculations for fission and cluster decay of $^{76}Sr$ are presented for this nucleus to be in its ground-state or formed as an excited compound system in heavy-ion reactions. The predicted mass distribution, for the dynamical collective mass transfer process assumed for fission of $^{76}Sr$, is clearly asymmetric, favouring $α$-nuclei. Cluster decay is studied within a preformed cluster model, both for ground-state to ground-state decays and from excited compound system to the ground-state(s) or excited states(s) of the fragments.
We construct a formula for proton-nucleus total reaction cross section as a function of the mass and neutron excess of the target nucleus and the proton incident energy. We deduce the dependence of the cross section on the mass number and the proton incident energy from a simple argument involving the proton optical depth within the framework of a black sphere approximation of nuclei, while we describe the neutron excess dependence by introducing the density derivative of the symmetry energy, L, on the basis of a radius formula constructed from macroscopic nuclear models. We find that the cros…
The shell correction is proposed in the improved isospin dependent quantum molecular dynamics (ImIQMD) model, which plays an important role in heavy-ion fusion reactions near Coulomb barrier. By using the ImIQMD model, the static and dynamical fusion barriers, dynamical barrier distribution in the fusion reactions are analyzed systematically. The fusion and capture excitation functions for a series of reaction systems are calculated and compared with experimental data. It is found that the fusion cross sections for neutron-rich systems increase obviously, and the strong shell effects of two co…
Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHE have been recently produced with doubly-magic $^{48}$Ca beams. However, SHE synthesis experiments with single-magic $^{50}$Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for $Z=117,119$ superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in $^{48}$Ca,$…
We study the production of $K^+, ρ, ω$ and $ϕ$ mesons in $p + ^{12}C$ reactions on the basis of empirical spectral functions. The high momentum, high removal energy part of the spectral function is found to be negligible in all cases close to the absolute threshold. Furthermore, the two-step process ($pN \rightarrow πN N; πN \rightarrow N + K^+, ρ, ω, ϕ$) dominates the cross section at threshold energies in line with earlier calculations based on the folding model.
We study the effect of in-medium hadronic properties in photon nucleus interactions in the context of shadowing as well as the dilepton spectrum for incident photon energies in the range 1.1- 3 GeV. A reasonable agreement with the experimental data for shadowing is obtained in a scenario of downward spectral shift of the hadrons. We show that distinguishable features for in-medium changes of the hadronic properties can be observed experimentally through the dilepton spectrum by judicious choice of target nuclei and incident energy of photons.
