Breakup Reaction Research Articles

Evidence for a 3.8 MeV state inBe9

The breakup reaction $^{9}\mathrm{Be}(^{4}\mathrm{He},3\ensuremath{\alpha})\mathit{n}$ was measured using an array of four double-sided silicon strip detectors at beam energies of 22 and 26 MeV. Excited states in $^{9}\mathrm{Be}$ up to 8 MeV were populated and reconstructed through measurements of the charged reaction products. Evidence is given for a state in $^{9}\mathrm{Be}$ at $3.{82}_{\text{-0.09}}^{\text{+0.08}}$ MeV with $\mathrm{\ensuremath{\Gamma}}={1240}_{\text{-90}}^{\text{+270}}$ keV. This is consistent with two recent measurements of a state with similar properties in the mirror nucleus $^{9}\mathrm{B}$. An analysis of the reduced widths ($^{8}\mathrm{Be}_{\mathrm{g}.\mathrm{s}.}$ channel) of this state along with the proposed mirror state has led to a firm limit of $J\ensuremath{\le}7/2$ and a tentative assignment of ${J}^{\ensuremath{\pi}}=1/{2}^{\ensuremath{-}}$ or $3/{2}^{\ensuremath{-}}$.

A Common Optical Potential for 4He+12C at Intermediate Energies**Supported by the National Natural Science Foundation of China under Grant No 11205036, and the Fundamental Research Funds for the Central Universities of China under Grant No HEUCF101501.

A common optical potential for 4He+12C at intermediate bombarding energies, which is essential in analyzing exotic nuclei with 4He clusters, is obtained based on the São Paulo potential. Among systematic optical potentials for 4He+12C, this potential has the merit of using a fixed imaginary part of the Woods-Saxon form. By optical-model calculations, this potential reproduces the experimental elastic scattering angular distributions of 4He+12C well within the energy range of 26A–60A MeV. It is also applied successfully in calculations of the breakup reactions of 6Li+12C and 6He+12C with a three-body continuum discretized coupled-channel method.

No-capture breakup and incomplete fusion reactions induced by stable weakly bound nucleus 9Be

The reactions including the stable weakly bound nucleus 9Be have been studied using the classical trajectory model accompanied with the experimental breakup function and the Aage-Winther interaction potential (AW95). In these calculations, the no-capture breakup and the incomplete fusion cross-sections as well as their competition at around the Coulomb barrier have been investigated. Our calculations showed that at a given far-Coulomb-barrier energy the incomplete fusion reaction in different distributions of angular momentum and energies can dominate the no-capture breakup reaction. This dominating process is reversed at the near-barrier energies.

Microscopic analysis of 10,11Be elastic scattering on protons and 12C and breakup processes of 11Be within the 10Be+n cluster model

The elastic scattering cross-sections of 10,11Be on protons and 12C at energy E < 100 MeV/nucleon using microscopically calculated optical potentials (OP) are presented. The real OP is obtained by a folding procedure with effective NN interactions, while the imaginary OP is estimated within the high energy approximation (HEA). The spin-orbit part of the OP is also included. The characteristics of the breakup processes of 11Be on different nuclear targets are also considered. The cross-sections of diffractive breakup and stripping reactions of 11Be on 9Be, 93Nb, 181Ta and 238U at energy E = 63 MeV/nucleon and the longitudinal momentum distributions of 10Be fragments produced in the breakup of 11Be on these nuclei are presented. The results are in a good agreement with the available experimental data, in particular the obtained widths of about 50 MeV/c are closed to the empirical ones.

Fusion studies with low-intensity radioactive ion beams using an active-target time projection chamber

The total fusion excitation function for 10Be+40Ar has been measured over the center-of-momentum (c.m.) energy range from 12 to 24MeV using a time-projection chamber (TPC). The main purpose of this experiment, which was carried out in a single run of duration 90h using a ≈100 particle per second (pps) 10Be beam, was to demonstrate the capability of an active-target TPC to determine fusion excitation functions for extremely weak radioactive ion beams. Cross sections as low as 12mb were measured with acceptable (50%) statistical accuracy. It also proved to be possible to separate events in which charged particles were emitted from the fusion residue from those in which only neutrons were evaporated. The method permits simultaneous measurement of incomplete fusion, break-up, scattering, and transfer reactions, and therefore fully exploits the opportunities presented by the very exotic beams that will be available from the new generation of radioactive beam facilities.

Influence of experimental conditions on the spectroscopy investigation of 14Be by Coulomb breakup reaction**Supported by National Natural Science Foundation of China (11205036)

The two-body (core+2n) cluster structure was implemented to describe the two-neutron halo nucleus 14Be, where the core 12Be was assumed inert and at a ground state and the dineutron was assumed at a pure 2S0 state. Based on such a structure the three-body continuum-discretized coupled-channel (CDCC) calculation was successfully used to deal with the 14Be breakup reactions of 14Be + Pb at 35 MeV/u. Consequently, we modeled the kinematically complete measurement experiment of this reaction with the help of Geant4. With the simulation data the relative energy spectrum was constructed by the invariant mass method and B(E1) spectrum was extracted using the virtual photon model. The influence of the target thickness and detector performance on the energy spectroscopy was investigated.

Measuring the Neutron Signature of the t→d+n Triton Breakup Reaction and the Angle-Dependent Differential Cross Section of 6Li(n,t)4He at 2.32 MeV

The continuous neutron spectrum from the t→d+n breakup reaction can best be extracted in the 3H(p,n)3He and 4He(t,n)6Li reactions because of minimum neutron background in both cases. Only for the latter reaction are neutron background spectra also available. These data were measured at 11.88-MeV triton energy at eight angles between 0 and 120 deg. As a test for the validity of the procedure, angle-dependent differential cross sections of 4He(t,n)6Li were extracted and converted to 6Li(n,t)4He at En = 2.32 MeV by detailed balance calculation thus contributing to the R-matrix analysis of the 7Li system. The double-differential and neutron energy integrated cross sections at that energy are given as well as those for the triton breakup of the time-reversed reaction.

Elastic scattering and breakup ofBe11on protons at26.9AMeV

The elastic scattering and breakup of the halo nucleus $^{11}\mathrm{Be}$ on protons at an incident energy of $26.9A$ MeV have been measured. The $^{11}\mathrm{Be}+p$ elastic scattering cross sections at various energies, including the present one, are systematically analyzed with the Chapel Hill 89 (CH89) and Koning-Delaroche (KD) global optical model potentials (OMPs), and the corresponding normalization factors are obtained. An extended version of the continuum-discretized coupled-channels (XCDCC) formalism, including dynamic core excitation effects, is applied to analyze the elastic scattering and breakup data. It is found that the core excitation plays a moderate role in the elastic scattering and breakup reaction of the halo nucleus $^{11}\mathrm{Be}$, being consistent with previous results at higher energies.

Inclusive Proton Emission Spectra from Deuteron Breakup Reactions

We present calculations of deuteron elastic and nonelastic breakup cross sections and angular distributions at deuteron energies below 100 MeV obtained using the post-form DWBA approximation. The elastic breakup cross section was extensively studied in the past. Very few calculations of nonelastic breakup have been performed, however. We compare two forms of the elastic DWBA breakup amplitude but conclude that neither provides a correct description of the inclusive proton emission cross section.

Experimental study of Three-Nucleon Dynamics in the dp breakup reaction

An experiment to investigate the 1 H(d ,pp )n breakup reaction using a deuteron beam of 340, 380 and 400 MeV and the WASA detector has been performed at the Cooler Synchrotron COSY-Julich. The main goal was a detailed study of various aspects of fewnucleon dynamics like the three nucleon force (3NF), the long-range Coulomb interaction or relativistic effects in the medium energy region. The relativistic effects and their interplay with 3NF become more important with increasing available energy in the three nucleon system. The almost 4π geometry of the WASA detector provides an unique possibility to study various aspects of dynamics.The studies of the 3N system dynamics in the breakup reaction with BINA detector are continued in the Cyclotron Center Bronowice.

Study of11Li and10,11Be nuclei through elastic scattering and breakup reactions

The hybrid model of the microscopic optical potential (OP) is applied to calculate the 11 Li+p , 10,11 Be+p , and 10,11 Be+12 C elastic scattering cross sections at energies E Li+p elastic scattering, the microscopic large-scale shell model (LSSM) density of 11 Li is used, while the density distributions of 10,11 Be nuclei obtained within the quantum Monte Carlo (QMC) model and the generator coordinate method (GCM) are utilized to calculate the microscopic OPs and cross sections of elastic scattering of these nuclei on protons and 12 C. The depths of the real and imaginary parts of OP are fitted to the elastic scattering data, being simultaneously adjusted to reproduce the true energy dependence of the corresponding volume integrals. Also, the cluster models, in which 11 Li consists of 2n -halo and the 9 Li core having its own LSSM form of density and 11 Be consists of a n -halo and the 10 Be core, are adopted. Within the latter, we give predictions for the longitudinal momentum distributions of 9 Li fragments produced in the breakup of 11 Li at 62 MeV/nucleon on a proton target. It is shown that our results for the diffraction and stripping reaction cross sections in 11 Be scattering on 9 Be, 93 Nb, 181 Ta, and 238 U targets at 63 MeV/nucleon are in a good agreement with the available experimental data.

Reactions in the four-nucleon system above breakup threshold

Microscopic calculations of four-body scattering become very challenging in the energy regime above the threshold for four free particles. We consider mixed-isospin four-nucleon reactions initiated by the proton-3 H, neutron-3 He, or deuteron-deuteron collisions. We solve the Alt, Grassberger, and Sandhas equations for the four-nucleon transition operators in the momentum-space framework. The complex-energy method with special integration weights is applied to deal with the complicated singularities in the kernel of AGS equations. Results for the differential cross section and spin observables in elastic, charge-exchange, transfer, and breakup reactions using realistic potentials are presented.

Deuteron--Deuteron Collision at 160 MeV

The experiment was carried out using BINA detector at KVI in Groningen. For the first time an extensive data analysis of the data collected in back part of the detector is presented, where a clusterization method is utilized for angular and energy information. We also present differential cross-sections for the (dd$\rightarrow$dpn) breakup reaction within \textit{dp} quasi-free scattering limit and their comparison with first calculations based on Single Scattering Approximation (SSA) approach.

Study of cluster structures in10Be and16C neutron-rich nuclei via break-up reactions

Projectile break-up reactions induced on polyethylene (CH_2) target are used in order to study the spectroscopy of ^10Be and ^16C nuclei. For the present experiment we used ^10Be and ^16C beams delivered by the FRIBs facility at INFN-LNS, and the CHIMERA 4pi multi-detector. ^10Be and ^16C structures are studied via a relative energy analysis of break-up fragments. The ^4He+^6He break-up channel allowed us to study the spectroscopy of ^10Be; in particular we find evidence of a new state in ^10Be at 13.5 MeV excitation energy. The ^16C nucleus is studied via ^6He-^10Be correlation; we find the fingerprint of a possiblestate at about 20.6 MeV

Neutron-neutron quasifree scattering inndbreakup at 10 MeV

The neutron-deuteron (nd ) breakup reaction provides a rich environment for testing theoretical models of the neutron-neutron (nn ) interaction. Current theoretical predictions based on rigorous ab-initio calculations agree well with most experimental data for this system, but there remain a few notable discrepancies. The cross section for nn quasifree (QFS) scattering is one such anomaly. Two recent experiments reported cross sections for this particular nd breakup configuration that exceed theoretical calculations by almost 20% at incident neutron energies of 26 and 25 MeV [1, 2]. The theoretical values can be brought into agreement with these results by increasing the strength of the 1 S0 nn potential matrix element by roughly 10%. However, this modification of the nn effective range parameter and/or the 1 S0 scattering length causes substantial charge-symmetry breaking in the nucleon-nucleon force and suggests the possibility of a weakly bound di-neutron state [3].We are conducting new measurements of the cross section for nn QFS in nd breakup. The measurements are performed at incident neutron beam energies below 20 MeV. The neutron beam is produced via the 2 H(d , n )3 He reaction. The target is a deuterated plastic cylinder. Our measurements utilize time-of-flight techniques with a pulsed neutron beam and detection of the two emitted neutrons in coincidence. A description of our initial measurements at 10 MeV for a single scattering angle will be presented along with preliminary results. Also, plans for measurements at other energies with broad angular coverage will be discussed.

Experimental Studies of the Coulomb Force Effects in Deuteron-Proton Break-up Reaction at Medium Energy Regime

A set of differential cross-section data of the 1 H(d, pp)n breakup reaction at 130 and 160 MeV deuteron beam energies has been measured in the forward polar angles domain. The data were collected with the use of the Germanium Wall (FZ Julich) and BINA (KVI Groningen) detectors. This part of the phase-space is special with respect to the dominant Coulomb force influence on the system dynamics. The data are compared with the theoretical calculations based on the Argonne V18 potential supplemented with the long-range electromagnetic component. The predictions also include the Urbana IX three nucleon force model. The strongest Coulomb effects are found in regions where the relative energy of the two protons is the smallest.

Reaction theory: Status and perspectives

The current status of the reaction theory of nuclear collisions involving weakly-bound exotic nuclei is presented. The problem is addressed within the Continuum Discretized Coupled Channel (CDCC) framework, recalling its foundations and applications, as well as its connection with the Faddeev formalism. Recent developments and improvements of the method, such as core and target excitations and the extension to three-body projectiles, are presented. The use of the CDCC wave function in the calculation of inclusive breakup reactions is also introduced.

Evaluation of inclusive breakup cross sections in reactions induced by weakly-bound nuclei within a three-body model

In 1980s Ichimura, Austern and Vincent [Phys.Rev.C 32, 431 (1985)] proposed a quantum mechanical theory to study the problem of inclusive breakup cross sections in the nuclear reactions. Using the DWBA version of this model, applications to deuteron and 6 Li inclusive breakup reactions are presented and compared with some available data.

Contribution of three nucleon force investigated in deuteron-proton breakup reaction

The elastic scattering and deuteron breakup data were collected in the experiment performed at KVI (Groningen) with use of unpolarized deuteron beam with energy of 80 MeV per nucleon, impinging on hydrogen target. The procedure applied to determine total integrated luminosity is presented. The result will be used for normalization of the differential cross section for the deuteron-proton breakup reaction.

Resonance model for the three-body states of the A=6 reactions

We present an R -matrix-based model for three-body final states that has aspects of the Faddeev approach to three-particle scattering. The model is applied to describing the nucleon spectra for breakup reactions in the A = 6 systems. Calculations using a charge-symmetric parametrization agree fairly well with the experimental data, although they indicate larger contributions from the 5 He or 5 Li ground state are necessary.