Breakup Of 8B Research Articles

Dynamics of open quantum nuclear systems: the case of 8B breakup

Dynamics of open quantum nuclear systems: the case of 8B breakup

Breakup of the proton halo nucleus 8B near barrier energies

The dynamics of a nuclear open quantum system could be revealed in the correlations between the breakup fragments of halo nuclei. The breakup mechanism of a proton halo nuclear system is of particular interest as the Coulomb polarization may play an important role, which, however, remains an open question. Here we use a highly efficient silicon detector array and measure the correlations between the breakup fragments of 8B incident on 120Sn at near-barrier energies. The energy and angular correlations can be explained by a fully quantum mechanical method based on the state-of-the-art continuum discretized coupled channel calculations. The results indicate that, compared to the neutron halo nucleus 6He, 8B presents distinctive reaction dynamics: the dominance of the elastic breakup. This breakup occurs mainly via the short-lived continuum states, almost exhausts the 7Be yield, indicating the effect of Coulomb polarization on the proton halo state. The correlation information reveals that the prompt breakup mechanism dominates, occurring predominantly on the outgoing trajectory. We also show that, as a large environment, the continuum of 8B breakup may not significantly influence elastic scattering and complete fusion.

Role of the diagonal and off-diagonal continuum–continuum couplings in the breakup of 8B and 19C on 58Ni and 208Pb targets

Abstract The role of the diagonal and off-diagonal continuum–continuum couplings on Coulomb + nuclear, Coulomb and nuclear breakup cross sections is investigated for the 8B + 58Ni, 8B + 208Pb and 19C + 208Pb at 29.3, 170.3 and 1273 MeV incident energies respectively. Qualitatively, we found that, the diagonal continuum–continuum couplings are responsible for the large reduction of the differential Coulomb + nuclear and nuclear differential breakup cross sections at backward angles. At forward angles, this reduction is due to the off-diagonal continuum–continuum couplings. In the absence of these couplings, the nuclear breakup is the more dominant process, while when they are included, the Coulomb breakup becomes dominant. This shows that, the nuclear breakup is more affected by the continuum–continuum couplings than its Coulomb counterpart. Quantitatively, we found that, the off-diagonal continuum–continuum couplings reduce by 13.39%, 12.71% and 11.11% the Coulomb + nuclear breakup cross sections for the 8B + 58Ni, 8B + 208Pb and 19C + 208Pb reactions, respectively.

Breakup, fusion, and elastic scattering analysis of the8B +58Ni system at low energies with the continuum-discretized coupled channels method

We have performed continuum-discretized coupled channels (CDCC) calculations of the breakup of 8B on 58Ni in the energy interval 10 – 26 MeV in the c.m. system. Elastic scattering angular distributions for the 8B + 58Ni system at five different energies around the Coulomb barrier were studied by using the CDCC model and taking into account a coupling between elastic and breakup channels. The energy-dependent sets found for the OPs parameters reproduce well the elastic scattering data and the fusion and reaction cross sections. Finally, a comparison of the reduced total reaction cross sections for the 8B + 58Ni system with the 6He + 208Pb and 6He + 209Bi systems is presented.

17F breakup reactions: A touchstone for indirect measurements

Dissociation has become an essential tool in several domains of nuclear physics. It provides useful information about the structure of halo nuclei, and Coulomb breakup can be used as an indirect method to measure radiative-capture cross sections at stellar energies. Though simple it may seem, this indirect technique relies on peculiar assumptions. Recent theoretical analyses of the Coulomb breakup of 8B have shown that these assumptions are not all satisfied.Whereas many experimental investigations on such a phenomenon have been conducted on 8B, the case of 17F has been poorly addressed up to now. An exclusive study of 17F breakup reactions has thus been performed at the FRIBs facility of the Laboratori Nazionali del Sud, Catania (Italy). The experimental setup and the detector systems allowed the measurement, event-by-event, of the X-Y coordinates of the interaction point on the target as well as the momenta and angles of all outgoing decay particles with a geometrical efficiency of 72% and a resolution of approximately 300 keV.The first results and preliminary model comparison are reported.

Interplay between the 8B breakup and other reaction mechanisms by means of CDCC method

We use the continuum discretized coupled channel method to study the effects of breakup on different reaction mechanisms for the 8B + 58Ni system. We devote special attention to the role of continuum-continuum couplings.

New measurements on breakup of 8B + 58Ni at energies around the coulomb barrier

New breakup cross section measurements for 8B + 58Ni are reported, obtained by detecting the 7Be products at forward angles (±45°) for 25.0, 26.9, and 28.4-MeV bombarding energies. The obtained results are consistent with those at 25.75 MeV, measured previously. Continuum-discretized coupled-channel calculations are performed and compared to the data.

Full coupled-channel description of three-body and four-body breakup reactions

Recent development of the continuum-discretized coupled-channels method (CDCC) is reported with introducing the eikonal CDCC method (E-CDCC) and four-body CDCC. The former is applied to analysis of 8B breakup by 208Pb at 52 A MeV and the astrophysical factor S 17 ( 0 ) for the 7Be( p , γ ) 8B reaction is extracted with the asymptotic normalization coefficient method. We obtain S 17 ( 0 ) = 20.9 −1.9 +2.0 eV b , which is significantly larger than the previous one, S 17 ( 0 ) = 18.9 ± 1.8 eV b , determined from an analysis with the virtual photon theory. The difference between the two values is found to be due to the contributions from nuclear breakup and higher-order processes. The latter, four-body CDCC, is applied to 6He+ 209Bi scattering near the Coulomb barrier energy and found to reproduce the elastic cross sections well, in contrast to the standard three-body CDCC. Accurate treatment of the three-body continuum states of 6He turns out to be essential to correctly describe the 6He+ 209Bi scattering.

Searching for a polarization potential in the breakup of 8B

Continuum couplings are extremely important to describe the breakup of loosely bound nuclei. We explore the various methods of extracting a polarization potential, as an effective representation of these couplings in the breakup channel. Our application consists of 8B→7Be+p on 58Ni at near-barrier energies. We find that the standard ways of determining polarization potentials are not useful to describe the breakup cross section in terms of a one-step process. Our results indicate that continuum couplings are strongly non-local and the complexity of coupled channel methods may well be unavoidable.

Breakup of loosely bound nuclei as indirect method in nuclear astrophysics: 8B, 9C, 23Al

We discuss the use of one-nucleon breakup reactions of loosely bound nuclei at intermediate energies as an indirect method in nuclear astrophysics. These are peripheral processes, therefore we can extract asymptotic normalization coefficients (ANC) from which reaction rates of astrophysical interest can be inferred. To show the usefulness of the method, three different cases are discussed. In the first, existing experimental data for the breakup of 8B at energies from 30 to 1000 MeV/u and of 9C at 285 MeV/u on light through heavy targets are analyzed. Glauber model calculations in the eikonal approximation and in the optical limit using different effective interactions give consistent, though slightly different results, showing the limits of the precision of the method. The results lead to the astrophysical factor S_17(0)=18.7+/-1.9 eVb for the key reaction for solar neutrino production 7Be(p,\gamma)8B. It is consistent with the values from other indirect methods and most direct measurements, but one. Breakup reactions can be measured with radioactive beams as weak as a few particles per second, and therefore can be used for cases where no direct measurements or other indirect methods for nuclear astrophysics can be applied. We discuss a proposed use of the breakup of the proton drip line nucleus 23Al to obtain spectroscopic information and the stellar reaction rate for 22Mg(p,\gamma)23Al.

Re-evaluation of the low-energy Coulomb-dissociation cross section of 8B and the astrophysical S17 factor

An exclusive measurement of the Coulomb breakup of 8B into 7Be+p at 254 AMeV was used to infer the low-energy 7Be(p,γ)8B cross section. Particular emphasis was placed on the angular correlations of the breakup particles which demonstrate clearly that E1 multipolarity dominates within the angular cuts selected for the analysis. The deduced astrophysical S17 factors exhibit good agreement with the most recent direct 7Be(p,γ)8B measurements.

Transfer to the continuum and breakup reactions

Reaction theory is an essential ingredient when performing studies of nuclei far from stability. One approach for the calculation of breakup reactions of exotic nuclei into two fragments is to consider inelastic excitations into the single particle continuum of the projectile. Alternatively one can also consider the transfer to the continuum of a system composed of the light fragment and the target. In this work we make a comparative study of the two approaches, underline the different inputs, and identify the advantages and disadvantages of each approach. Our test cases consist of the breakup of 11Be on a proton target at intermediate energies, and the breakup of 8B on 58Ni at energies around the Coulomb barrier. We find that, in practice the results obtained in both schemes are in semiquantitative agreement. We suggest a simple condition that can select between the two approaches.

Sensitivity of 8B breakup cross section to projectile structure in CDCC calculations

Given the astrophysical interest of 7Be(p, γ)8B, there have been several experiments applying the Coulomb dissociation method for extracting the capture rate. Measurements at Michigan State are dominated by E1 contributions but have a small E2 component. On the other hand, a lower energy measurement at Notre Dame has a much stronger E2 contribution. The expectation was that the two measurements would tie down the E2 and thus allow for an accurate extraction of the E1 relevant for the capture process. The aim of this paper is to show that the E2 factor in breakup reactions does not translate into a scaling of the E2 contribution in the corresponding capture reaction. We show that changes to the 8B single particle parameters, which are directly related to the E2 component in the capture reaction, do not affect the corresponding breakup reactions, using the present reaction theory.

Breakup of loosely bound nuclei at intermediate energies as indirect method in nuclear astrophysics: 8B, 9C and the S17, S18 astrophysical factors

We discuss the use of one-nucleon breakup reactions of loosely bound nuclei at intermediate energies as an indirect method in nuclear astrophysics. In particular, the breakup of 8B and 9C is described in detail in terms of an extended Glauber model. Existing experimental data for the breakup of 8B at energies from 30 to 1000 MeV/u and of 9C at 285 MeV/u on light through heavy targets are analyzed. The predictions of the model are in excellent agreement with independent reaction data (reaction cross sections and parallel momentum distributions for core-like fragments). Final state interaction has been included in the Coulomb dissociation component. Glauber model calculations using different effective interactions give consistent, though slightly different results. The results of this new analysis are compared with the earlier one for the astrophysical factor S17(0) for the key reaction for solar neutrino production 7Be(p,γ)8B. They are consistent with the values from most direct measurements and other indirect methods.

Coulomb dissociation of 8B and the low-energy cross section of the 7Be(p,gamma)8B solar fusion reaction.

An exclusive measurement of the Coulomb breakup of 8B into 7Be+p at 254A MeV allowed the study of the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates and that E2 multipolarity can be neglected. By using a simple single-particle model for 8B and treating the breakup in first-order perturbation theory, we extract a zero-energy S factor of S17(0)=18.6+/-1.2+/-1.0 eV b, where the first error is experimental and the second one reflects the theoretical uncertainty in the extrapolation.

Determination of the S17 and S18 astrophysical factors from the breakup of 8B and 9C at intermediate energies

We show that asymptotic normalization coefficients can be extracted from one nucleon breakup reactions of loosely bound nuclei at 30–300 MeV/u. In particular, the breakup of 8B and 9C is described in terms of an extended Glauber model. The 8B ANC extracted from existing breakup data at several energies and on different targets, C tot 2 = 0.450 ± 0.039 fm −1, leads to the astrophysical factor S 17(0) = 17.4 ± 1.5 eV·b for the key reaction for solar neutrino production, 7Be( p, γ) 8B. We also find S 18(0) = 46 ± 6 eV·b from the breakup of 9C at 285 MeV/u. Glauber model calculations in the eikonal approximation and in the optical limit using different effective interactions give consistent results. The procedure described provides an indirect method to determine reaction rates of astrophysical interest with beams of loosely bound radioactive nuclei.

High-energy breakup of 8B

High-energy breakup of 8B

Coulomb breakup of 8B and the flux of 8B neutrinos from the Sun

Coulomb breakup of 8B and the flux of 8B neutrinos from the Sun

Nuclear and coulomb interaction in 8B breakup at sub-coulomb energies

The angular distribution for the breakup of 8B-->7Be+p on a 58Ni target has been measured at an incident energy of 25.75 MeV. The data are inconsistent with first-order theories but are remarkably well described by calculations including higher-order effects. The comparison with theory illustrates the importance of the inclusion of the exotic proton halo structure of 8B in accounting for the data.

Breakup of 8B and the 7Be(p, γ)8B reaction

The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the $^7$Be($p,\gamma)^8$B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain as various measurements differ from each other by 30-40 %. The Coulomb dissociation process which reverses the radiative capture by the dissociation of $^8$B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages (like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis of the breakup of $^8$B and discuss the current status of the low-energy cross sections (or the astrophysical $S$-factor) of the $^7$Be($p,\gamma)^8$B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested.