Cluster Expansion of Cold Alpha Matter Energy

In the cluster expansion framework of Bose liquids we calculate analytical expressions of the two-body, three-body and four-body diagrams contributing to the g.s. energy of an infinite system of neutral alpha-particles at zero-temperature, interacting via the strong nuclear forces exclusively. This is analytically tractable by assuming a density dependent two-body correlation function of Gaussian type. For the alpha-alpha potential we adopt the phenomenological Ali-Bodmer interaction and semi-microscopic potentials obtained from the Gogny force parametrizations. We show that under such assumptions we achieve a rapid convergence in the cluster expansion, the four-body contributions to the energy being smaller than the two-body and three-body contributions by at least an order of magnitude.Comment: 22 pages, 13 figure

Imaginary part of the C 9 − Be 9 single-folded optical potential

In a recent publication we have argued that using two very successful n\text{\ensuremath{-}}^{9}\mathrm{Be} optical potentials [A. Bonaccorso and R. J. Charity, Phys. Rev. C 89, 024619 (2014)] and microscopic projectile densities, it is possible to build a single-folded (light-) nucleus-$^{9}\mathrm{Be}$ imaginary optical potential which is more accurate than a double-folded optical potential. By comparing to experimental reaction cross sections, we showed for $^{8}\mathrm{B},\phantom{\rule{0.16em}{0ex}}^{8}\mathrm{Li}$, and $^{8}\mathrm{C}$ projectiles, that a very good agreement between theory and data could be obtained with such a ``bare'' potential, at all but the lowest energies where a small semimicroscopic surface term was added to the single-folded potential to take into account projectile breakup. In this paper we extend this study to the case of $^{9}\mathrm{C}$ projectiles and assess the sensitivity to the projectile density used. We then obtained the modulus of the nucleus-nucleus $S$ matrix and parametrize it in terms of a strong-absorption radius ${R}_{s}$ and finally extracted the phenomenological energy dependence of this radius. This approach could be the basis for a systematic study of optical potentials for light exotic nuclei scattering on light targets and/or parametrizations of the $S$ matrix. Furthermore our study will serve to make a quantitative assessment of the description of the core-target part of knockout reactions, in particular their localization in terms of impact parameters

Extended sudden approximation model for high-energy nucleon removal reactions

A model based on the sudden approximation has been developed to describe high energy single nucleon removal reactions. Within this approach, which takes as its starting point the formalism of Hansen \cite{Anne2}, the nucleon-removal cross section and the full 3-dimensional momentum distributions of the core fragments including absorption, diffraction, Coulomb and nuclear-Coulomb interference amplitudes, have been calculated. The Coulomb breakup has been treated to all orders for the dipole interaction. The model has been compared to experimental data for a range of light, neutron-rich psd-shell nuclei. Good agreement was found for both the inclusive cross sections and momentum distributions. In the case of $^{17}$C, comparison is also made with the results of calculations using the transfer-to-the-continuum model. The calculated 3-dimensional momentum distributions exhibit longitudinal and transverse momentum components that are strongly coupled by the reaction for s-wave states, whilst no such effect is apparent for d-waves. Incomplete detection of transverse momenta arising fromlimited experimental acceptances thus leads to a narrowing of the longitudinal distributions for nuclei with significant s-wave valence neutron configurations, as confirmed by the data. Asymmetries in the longitudinal momentum distributions attributed to diffractive dissociation are also explored.Comment: 16 figures, submitted to Phys. Rev.

Scattering of 7^{7}Be and 8^{8}B and the astrophysical S17_{17} factor

Measurements of scattering of $^{7}$Be at 87 MeV on a melamine (C$_{3}$N$_{6}$H$_{6}$) target and of $^{8}$B at 95 MeV on C were performed. For $^{7}$Be the angular range was extended over previous measurements and monitoring of the intensity of the radioactive beam was improved. The measurements allowed us to check and improve the optical model potentials used in the incoming and outgoing channels for the analysis of existing data on the proton transfer reaction $^{14}$N($^{7}$Be,$^{8}$B)$^{13}$C. The resultslead to an updated determination of the asymptotic normalization coefficient for the virtual decay $^{8}$B $\to$ $^{7}$Be + $p$. We find a slightly larger value, $C_{tot}^{2}(^{8}B)=0.466\pm 0.047$ fm$^{-1}$, for the melamine target. This implies an astrophysical factor, $S_{17}(0)=18.0\pm 1.8$ eV$\cdot$b, for the solar neutrino generating reaction $^{7}$Be($p$,$\gamma$)$^{8}$B.Comment: 7 pages, 4 figure

Asymptotic normalization coefficient of ^{8}B from breakup reactions and the S_{17} astrophysical factor

We show that asymptotic normalization coefficients (ANC) can be extracted from one nucleon breakup reactions of loosely bound nuclei at 30-300 MeV/u. In particular, the breakup of ^{8}B is described in terms of an extended Glauber model. The 8B ANC extracted for the ground state of this nucleus from breakup data at several energies and on different targets, C^2 = 0.450+/-0.039} fm^-1, leads to the astrophysical factor S_{17}(0)= 17.4+/-1.5 eVb for the key reaction for solar neutrino production 7Be(p,gamma)8B. The procedure described here is more general, providing an indirect method to determine reaction rates of astrophysical interest with beams of loosely bound radioactive nuclei.Comment: 4 pages, RevTex, 3 figures revised version to appear in Phys Rev Let

Peripheral elastic and inelastic scattering of O 17 , 18 on light targets at 12 MeV/nucleon

A study of interaction of neutron rich oxygen isotopes $^{17,18}$O with light targets has been undertaken in order to determine the optical potentials needed for the transfer reaction $^{13}$C($^{17}$O,$^{18}$O)$^{12}$C. Optical potentials in both incoming and outgoing channels have been determined in a single experiment. This transfer reaction was used to infer the direct capture rate to the $^{17}$F(p,$\gamma$)$^{18}$Ne which is essential to estimate the production of $^{18}$F at stellar energies in ONe novae. The success of the asymptotic normalization coefficient (ANC) as indirect method for astrophysics is guaranteed if the reaction mechanism is peripheral and the DWBA cross section calculations are warranted and stable against OMP used. We demonstrate the stability of the ANC method and OMP results using good quality elastic and inelastic scattering data with stable beams before extending the procedures to rare ion beams. The peripherality of our reaction is inferred from a semiclassical decomposition of the total scattering amplitude into barrier and internal barrier components. Comparison between elastic scattering of $^{17}$O, $^{18}$O and $^{16}$O projectiles is made.Comment: 14 pages, 19 figure

Reaction and proton-removal cross sections of 6^6Li, 7^7Be, 10^{10}B, 9,10,11^{9,10,11}C, ^{12N, 13,15^{13,15}O and 17^{17}Ne on Si at 15 to 53 MeV/nucleon

Excitation functions for total reaction cross sections, $\sigma_R$, were measured for the light, mainly proton-rich nuclei $^6$Li, $^7$Be, $^{10}$B, $^{9,10,11}$C, $^{12}$N, $^{13,15}$O, and $^{17}$Ne incident on a Si telescope at energies between 15 and 53 MeV/nucleon. The telescope served as target, energy degrader and detector. Proton-removal cross sections, $\sigma_{2p}$ for $^{17}$Ne and $\sigma_p$ for most of the other projectiles, were also measured. The strong absorption model reproduces the $A$-dependence of $\sigma_R$, but not the detailed structure. Glauber multiple scattering theory and the JLM folding model provided improved descriptions of the measured $\sigma_R$ values. $rms$ radii, extracted from the measured $\sigma_R$ using the optical limit of Glauber theory, are in good agreement with those obtained from high energy data. One-proton removal reactions are described using an extended Glauber model, incorporating second order noneikonal corrections, realistic single particle densities, and spectroscopic factors from shell model calculations.Comment: 16 pages, 6 figure

Breakup of B-8 and the S-17 astrophysical factor reexamined

Journals published by the American Physical Society can be found at http://publish.aps.org/Existing experimental data for the breakup of B-8 at energies from 30 to 1000 MeV/nucleon on light through heavy targets are analyzed in detail in terms of an extended Glauber model. The predictions of the model are in excellent agreement with independent reaction data (reaction cross sections and parallel momentum distributions for corelike fragments). Final-state interactions have been included in the Coulomb dissociation component. We extract asymptotic normalization coefficients (ANC) from which the astrophysical factor S-17(0) for the key reaction for solar neutrino production, Be-7(p,gamma)B-8, can be evaluated. Glauber model calculations using different effective interactions give consistent, though slightly different results. The differences give a measure of the precision one can expect from the method. The unweighted average of all ANCs extracted leads to S-17(0)=18.7+/-1.9 eV b. The results of this new analysis are compared with the earlier one. They are consistent with the values from most direct measurements and other indirect methods

Single-Proton Removal Reaction Study of 16B

The low-lying level structure of the unbound system $^{16}$B has been investigated via single-proton removal from a 35 MeV/nucleon $^{17}$C beam. The coincident detection of the beam velocity $^{15}$B fragment and neutron allowed the relative energy of the in-flight decay of $^{16}$B to be reconstructed. The resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is argued that this feature corresponds to a very narrow ($\Gamma \ll$100 keV) resonance, or an unresolved multiplet, with a dominant $\pi (p_{3/2})^{-1} \otimes \nu (d_{5/2}^3)_{J=3/2^+}$ + $\pi (p_{3/2})^{-1} \otimes \nu (d_{5/2}^2,s_{1/2})_{J=3/2^+}$ configuration which decays by d-wave neutron emission.Comment: 16 pages, 5 figures, 1 table, submitted to Phys. Lett.