We study the near-threshold photoproduction of $η^\prime$ mesons from nuclei in coincidence with forward going protons in the kinematical conditions of the Crystal Barrel/TAPS experiment, recently performed at ELSA. The calculations have been performed within a collision model based on the nuclear spectral function. The model accounts for both the primary $γp \to {η^\prime}p$ process and the two-step intermediate nucleon rescattering processes as well as the effect of the nuclear $η^\prime$ mean-field potential. We calculate the exclusive $η^\prime$ kinetic energy distributions for the $^{12}$C($γ$, ${η^\prime}p$) reaction for different scenarios of $η^\prime$ in-medium modification. We find that the considered two-step rescattering mechanism plays an insignificant role in ${η^\prime}p$ photoproduction off the carbon target. We also demonstrate that the calculated $η^\prime$ kinetic energy distributions in primary photon--proton ${η^\prime}p$ production reveal strong sensitivity to the depth of the real ${η^\prime}$ potential at normal nuclear matter density (or to the ${η^\prime}$ in-medium mass shift) in the studied incident photon energy regime. Therefore, such observables may be useful to help determine the above ${η^\prime}$ in-medium renormalization from the comparison of the results of our calculations with the data from the CBELSA/TAPS experiment. In addition, we show that these distributions are also strongly influenced by the momentum-dependent optical potential, which the outgoing participant proton feels inside the carbon nucleus. This potential should be taken into account in the analysis of these data with the aim to obtain information on the ${η^\prime}$ modification in cold nuclear matter.
Color transparency is studied for the $K^+$ meson produced due to large four-momentum transfer in the $(e,e^\prime)$ reaction on nuclei. The variation of the $K^+$ meson color transparency ($K^+$CT) with the photon virtuality, and kaon momentum is investigated. The calculated results for $K^+$CT are compared with the data reported from Jefferson Laboratory.
We study the photoproduction of $η^\prime$ mesons from nuclei near the threshold within the collision model based on the nuclear spectral function. The model takes properly into account both primary photon-nucleon and secondary pion-nucleon $η^\prime$ production processes as well as the effect of the nuclear $η^\prime$ mean-field potential on these processes. We find that the secondary pion-induced reaction channel $πN \to {η^\prime}N$ plays an insignificant role in the $η^\prime$ photoproduction off nuclei. We calculate the transparency ratio for $eta^\prime$ mesons and compare it to the avai…
Halo nuclei are exotic nuclei which exhibit a strongly clusterised structure: they can be seen as one or two valence nucleons loosely bound to a core. Being observed at the ridge of the valley of stability, halo nuclei are studied mostly through reactions. In this contribution the reaction models most commonly used to analyse experimental data are reviewed and compared to one another. A reaction observable built on the ratio of two angular distributions is then presented. This ratio enables removing most of the sensitivity to the reaction mechanism, which emphasises the effects of nuclear stru…
The clear separation of scales observed in halo nuclei between the extended halo and the compact core makes these exotic nuclei a perfect subject for Effective Field Theory (EFT). Such description leads to a systematic expansion of the core-halo Hamiltonian, which naturally orders the nuclear-structure observables. In this short review, I show the advantage there is to include Halo-EFT descriptions within precise models of reactions. It helps identifying the nuclear-structure observables that matter in the description of the reactions, and enables us to easily bridge predictions of nuclear-str…
In many instances, single nucleon removal reactions from neutron-proton asymmetric projectile nuclei populate final states in the residual nuclei that are very weakly bound. Familiar examples include neutron removal reactions from neutron-rich $^{11}$Be and $^{12}$Be, the latter populating the well-known $1/2^+$ halo ground-state and $1/2^-$ excited-state of $^{11}$Be - both states less than 1 MeV from the first neutron-decay threshold. Numerous additional examples arise in reactions of asymmetric $p$- and $sd$-shell nuclei. The importance of this weak residue binding upon calculated single-nu…
The Transfer to the Continuum method has been applied to describe the $^{11}\text{Li}(p,pn)$ and $^{14}\text{Be}(p,pn)$ reactions in inverse kinematics, using structure overlaps computed within a full three-body model for the projectile. Calculations agree with the available experimental data on the unbound $^{10}$Li and $^{13}$Be nuclei.
In this contribution to the proceedings of the International Nuclear Physics Conference 2019, I review recent developments made in reaction models used to analyse data measured at radioactive-ion beam facilities to study exotic nuclear structures. I focus in particular on reactions like elastic scattering and breakup, which are used to study halo nuclei. Although these peculiar nuclei challenge usual nuclear-structure models, some can now be computed ab initio. This brief review illustrates the progresses made in nuclear-reaction theory in the last few years to improve the description of the p…
There exist model calculations showing the modification of the hadronic parameters of $ρ$ meson in the nuclear environment. From these parameters, we extract the $ρ$ meson nucleus optical potential and show the medium effect due to this potential on the $ρ$ meson mass distribution spectra in the photonuclear reaction. The calculated results reproduced reasonably the measured $e^+e^-$ invariant mass, i.e., $ρ$ meson mass, distribution spectra in the $( γ, ρ^0 \to e^+e^- )$ reaction on nuclei.
An experimental overview of reactions induced by the stable, but weakly-bound nuclei 6Li, 7Li and 9Be, and by the exotic, halo nuclei 6He, 8B, 11Be and 17F on medium-mass targets, such as 58Ni, 59Co or 64Zn, is presented. Existing data on elastic scattering, total reaction cross sections, fusion processes, breakup and transfer channels are discussed in the framework of a CDCC approach taking into account the breakup degree of freedom.
Atomic nuclei are composite systems, and they may be dynamically excited during nuclear reactions. Such excitations are not only relevant to inelastic scattering but they also affect other reaction processes such as elastic scattering and fusion. The coupled-channels approach is a framework which can describe these reaction processes in a unified manner. It expands the total wave function of the system in terms of the ground and excited states of the colliding nuclei, and solves the coupled Shrödinger equations to obtain the $S$-matrix, from which several cross sections can be constructed. Thi…
Electromagnetic reactions on light nuclei are fundamental to advance our understanding of nuclear structure and dynamics. The perturbative nature of the electromagnetic probes allows to clearly connect measured cross sections with the calculated structure properties of nuclear targets. We present an overview on recent theoretical ab-initio calculations of electron-scattering and photonuclear reactions involving light nuclei. We encompass both the conventional approach and the novel theoretical framework provided by chiral effective field theories. Because both strong and electromagnetic intera…
The differential cross sections of the forward coherent $ω$ and $ϕ$ mesons photoproduction from nuclei have been calculated using the Glauber model for the nuclear reaction. The measured cross section of the elementary reaction, i.e., $γN \to ω(ϕ) N$ reaction, are used as input in the Glauber model. The experimentally determined free-space scattering parameters of the quoted mesons have been used to evaluate the meson nucleus interactions. The sensitivity of the cross section to the Fermi-motion of the nucleon and the nucleon-nucleon short-range correlation in the nucleus are studied. The calc…
A new method is proposed to deduce the neutron radii of neutron-rich nuclei. This method requires measuring the reaction cross sections of both the neutron-rich nucleus and its stable isotope at the same energy on a proton target. Using this method and the available experimental data of $^{12,22}$C + $p$ and $^{9,14}$Be + $p$ at 40$A$ MeV, the neutron radii of $^{22}$C and $^{14}$Be have been deduced for the first time.
Background: Multi-nucleon transfer reactions have recently attracted attention as a possible path to the synthesis of new neutron-rich heavy nuclei. Purpose: We study transfer reactions involving massive nuclei with the intention of understanding if the semi-classical model GRAZING coupled to an evaporation and fission competition model can satisfactory reproduce experimental data on transfer reactions in which fission plays a role. Methods: We have taken the computer code GRAZING and have added fission competition to it (GRAZING-F) using our current understanding of $Γ_n/Γ_f$, fission barrier…
We discuss recent work on Coulomb dissociation and an effective-range theory of low-lying electromagnetic strength of halo nuclei. We propose to study Coulomb dissociation of a halo nucleus bound by a zero-range potential as a homework problem. We study the transition from stripping to bound and unbound states and point out in this context that the Trojan-Horse method is a suitable tool to investigate subthreshold resonances.
We propose to extend the optimal Fermi averaging procedure theoretically in order to calculate an in-medium $K^-n\to π^- Λ$ amplitude for the exothermic ($K^-$, $π^-$) reaction on nuclei in the framework of a distorted-wave impulse approximation, taking into account the local momentum transfer generated by semiclassical distorted waves for $K^-$ and $π^-$ mesons. Angular distributions for the $^{12}$C($K^-$, $π^-$)$^{12}_Λ$C reaction in which a momentum transfer is $q \lesssim$ 80 MeV/$c$ at $p_K=$ 800 MeV/$c$ in the $π^-$ forward direction, are estimated by applying the extended procedure. Th…
For the forward going proton and $η$ meson, the coherent $η$ meson production in the $(p,p^\prime)$ reaction on the spin-isospin saturated nucleus occurs only due to the $η$ meson exchange interaction between the beam proton and nucleus. In this process, the nucleon in the nucleus can be excited to resonances $N^*$ and the $η$ meson in the final state can arise due to $N^* \to Nη$. We investigate the dynamics of resonances, including nucleon Born terms, and their interferences in the coherently added cross section of this reaction. We discuss the importance of $N(1520)$ resonance and show the …
The transparency of the hadrons produced in the $γ(n,p) π^-$ reaction in nuclei is calculated using the Glauber model modified by including the Fermi motion of the nucleon in the nucleus. Since the calculated results underestimates the measured transparency for $^4$He nucleus, the Glauber model is further modified by incorporating the short-range correlation of the nucleon and the color transparency of the hadron in the nucleus. The nuclear transparency of the $γ(n,p) π^-$ reaction is calculated for $θ_{π^-}$(c.m.) = 50$^{\circ}$, 70$^{\circ}$ and 90$^{\circ}$. The calculated results are compa…
The fusion-by-diffusion model proposed by Swiatecki {\it et al.} [Phys. Rev. C71, 014602 (2005)] has provided a simple and convenient tool to estimate evaporation residue cross sections for superheavy nuclei. I extend this model by taking into account deformation of the target nucleus, and discuss the role of orientation of deformed target in hot fusion reactions at energies around the Coulomb barrier. To this end, I introduce an injection point for the diffusion process over an inner barrier which depends on the orientation angle. I apply this model to the $^{48}$Ca+$^{248}$Cm reaction and sh…
Cross sections for neutron-induced reactions from surrogate data: revisiting the Weisskopf-Ewing approximation for $(n,n^{\prime})$ and $(n,2n)$ reactions
With the development of radioactive beam facilities, studies concerning the shell evolution of unstable nuclei have recently gained prominence. Intruder components, particularly s-wave intrusion, in the low-lying states of light neutron-rich nuclei near N=8 are of importance in the study of shell evolution. The use of single-nucleon transfer reactions in inverse kinematics has been a sensitive tool that can be used to quantitatively investigate the single-particle orbital component of selectively populated states. The spin-parity, spectroscopic factor (or single-particle strength), and effecti…
Nuclear reaction rate ($λ$) is a significant factor in the process of nucleosynthesis. A multi-layer directed-weighted nuclear reaction network in which the reaction rate as the weight, and neutron, proton, $^4$He and the remainder nuclei as the criterion for different reaction-layers is for the first time built based on all thermonuclear reactions in the JINA REACLIB database. Our results show that with the increase of the stellar temperature ($T_{9}$), the distribution of nuclear reaction rates on the $R$-layer network demonstrates a transition from unimodal to bimodal distributions. Nuclei …
A self-contained Fortran-90 program based on a classical trajectory model with stochastic breakup is presented, which should be a powerful tool for quantifying complete and incomplete fusion, and breakup in reactions induced by weakly-bound two-body projectiles near the Coulomb barrier. The code calculates complete and incomplete fusion cross sections and their angular momentum distribution, as well as breakup observables (angle, kinetic energy and relative energy distributions).
We study the inclusive near-threshold production of $η^\prime$ mesons in $π^-$ meson-nucleus reactions on the basis of the first-collision model relying on the nuclear spectral function and including incoherent processes of $η^\prime$ production in $π^-$ meson--proton collisions. The model accounts for the absorption of initial $π^-$ and final $η^\prime$ mesons, the binding of intranuclear protons and their Fermi motion, as well as the effect of the scalar $η^\prime$--nucleus potential (or the in-medium shift of the $η^\prime$ meson mass) on these processes. We calculate the differential and t…
In this work, we reexamine the extension of the CDCC formalism to include target excitation and apply it to a variety of reactions to study the effect of breakup on inelastic cross sections. We use a transformed oscillator basis to discretize the continuum of the projectiles in the different reactions and use the extended CDCC method developed in this work to solve the resulting coupled differential equations. A new code has been developed to perform the calculations. Reactions 58Ni(d, d) 58Ni*, 24Mg(d, d) 24Mg* , 144Sm( 6Li, 6Li) 144Sm* and 9Be( 6Li, 6Li) 9Be* are studied. Satisfactory agreem…
Spectroscopic Amplitudes (SA) in the Interacting Boson Fermion Fermion Model (IBFFM) are necessary for the computation of $0νββ$ decays but also for cross sections of heavy-ion reactions, in particular, Double Charge Exchange reactions for the NUMEN collaboration, if one does not want to use the closure limit. We present for the first time: i) the formalism and operators to compute in a general case the spectroscopic amplitudes in the scheme IBFFM from an even-even to odd-odd nuclei, in a way suited to be used in reaction code, i.e., extracting the contribution of each orbital; 2) the odd-odd …
The structure and the energy spectrum of the $η^{\prime}$ mesonic nuclei are investigated in a relativistic mean field theory. One expects a substantial attraction for the $η^{\prime}$ meson in finite nuclei due to the partial restoration of chiral symmetry in the nuclear medium. Such a hadronic scale interaction for the $η^{\prime}$ mesonic nuclei may provide modification of the nuclear structure. The relativistic mean field theory is a self-contained model for finite nuclei which provides the saturation property within the model, and is good to investigate the structure change of the nucleus…
Spin dipole (SD) strengths for double beta-decay (DBD) nuclei were studied experimentally for the first time by using measured cross sections of (3He,t) charge exchange reactions (CERs). Then SD nuclear matrix elements (NMEs) for low-lying 2- states were derived from the experimental SD strengths by referring to the experimental GT (Gamow-Teller) and F (Fermi) strengths. They are consistent with the empirical SD NMEs based on the quasi-particle model with the empirical effective SD coupling constant. The CERs are used to evaluate the SD NME, which is associated with one of the major components…
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 have made a comparison of the neutron skins extracted from diverse experimental techniques with those obtained with Hartree-Fock-Bogoliubov calculations with 23 Skyrme and with 8 density-dependent interactions used in the relativistic mean field method. We have show…
We investigate the odd-even staggering (OES) in reaction cross sections of weakly bound nuclei with a Glauber theory, taking into account the pairing correlation with the Hartree-Fock-Bogoliubov (HFB) method. We first discuss the pairing gap in extremely weakly bound nuclei and show that the pairing gap persists in the limit of zero separation energy limit even for single-particle orbits with the orbital angular momenta $l=0$ and $l=1$. We then introduce the OES parameter defined as the second derivative of reaction cross sections with respect to the mass number, and clarify the relation betwe…
Photon-nuclear reaction in a transport model frame, namely an Extended Quantum Molecular Dynamics (EQMD) model, has been realised at the photon energy of 70-140 MeV in the quasi-deuteron (QD) regime. For an important application, we pay a special focus on photonuclear reactions of $^{12}$C($γ$,np)$^{10}$B where $^{12}$C is considered as different configurations including $α$-clustering. Obvious differences for some observables have been observed among different configurations, which can be attributed to spatial-momentum correlation of a neutron-proton pair inside nucleus, and therefore it give…
We investigate the spatial extension of weakly bound Ne and C isotopes by taking into account the pairing correlation with the Hartree-Fock-Bogoliubov (HFB) method and a 3-body model, respectively. We show that the odd-even staggering in the reaction cross sections of $^{30,31,32}$Ne and $^{14,15,16}$C are successfully reproduced, and thus the staggering can be attributed to the pairing anti-halo effect. A correlation between a one-neutron separation energy and the anti-halo effect is demonstrated for $s$- and p-waves using the HFB wave functions.
The $α$-decay phenomennon has been studied for more than a century but the mechanism of the $α$ particle formation and its tunneling process have not yet been fully understood. As an alternative to the $α$-decay lifetime measurement, we propose the proton-induced $α$ knockout reaction, ($p$,$pα$), as a new probe for the surface $α$ formation probability of $α$-decay nuclei. The $^{210,212}$Po($p$,$pα$)$^{206,208}$Pb reaction is described by the distorted-wave impulse approximation framework. It shows that the $^{212}$Po/$^{210}$Po ratio of the $α$ knockout cross sections agrees with that of th…
Chances of synthesis of transactinide nuclei in cold fusion reactions (one-neutron-out) reactions using radioactive beams are evaluated. Because intensities of radioactive beams are in most of the cases significantly lower than the ones of the stable beams, reactions with the highest radioactive beam intensities for the particular elements are considered. The results are compared with the recent ones obtained by Loveland who investigated the same nuclei.
The main progresses in the multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental progress and theoretical progress,the predicted production cross sections for unknown neutron-rich heavy nuclei and the trans-uranium nuclei are presented.
The activation cross sections of (d,p), (d,2n), (d,3n), and (d,2p) reactions on 63,65Cu were measured in the energy range from 4 to 20 MeV using the stacked-foils technique. Then, following the available elastic-scattering data analysis that provided the optical potential for reaction cross sections calculations, an increased effort has been devoted to the breakup mechanism, the direct reaction stripping, and the pre-equilibrium and compound-nucleus cross section calculations, corrected for the breakup and stripping decrease of the total reaction cross section. The overall agreement between th…
Background: Thick-target-induced nucleon-adding transfer reactions onto energetic rare-isotope beams are an emerging spectroscopic tool. Their sensitivity to single-particle structure complements one-nucleon removal reaction capabilities in the quest to reveal the evolution of nuclear shell structure in very exotic nuclei. Purpose: To add intermediate-energy, carbon-target-induced one-proton pickup reactions to the arsenal of $γ$-ray tagged direct reactions applicable in the regime of low beam intensities and to apply these for the first time to $fp$-shell nuclei. Methods: Inclusive and partia…
Background: One-nucleon knockout reactions provide insightful information on the single-particle structure of nuclei. When applied to one-neutron halo nuclei, they are purely peripheral, suggesting that they could be properly modeled by describing the projectile within a Halo Effective Field Theory (Halo-EFT). Purpose: We reanalyze the one-neutron knockout measurements of $^{11}$Be and $^{15}$C-both one-neutron halo nuclei-on beryllium at about 60MeV/nucleon. We consider Halo-EFT descriptions of these nuclei which already provide excellent agreement with breakup and transfer data. Method: We i…
Low-energy multinucleon transfer reactions are shown to be very effective tool for the production and spectroscopic study of light exotic nuclei. The corresponding cross sections are found to be significantly larger as compared with high energy fragmentation reactions. Several optimal reactions for the production of extremely neutron rich isotopes of elements with Z=6-14 are proposed.
