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In the first half of the paper, the nuclear astrophysics activities in Japan, especially in experimental studies are briefly overviewed. A variety of beams have been developed and used for nuclear astrophysics experiments in Japan. The activities include the RI beam facilities at low energies by the in-flight method at the Center for Nuclear Study (CNS), University of Tokyo and by the ISOL-based method at the JAERI tandem facility, and the RI beam facility at intermediate energies at RIKEN. Other activities include a study of the 12C(α, γ)16O reaction exclusively at the tandem accelerator at the Kyushu University, and studies at the neutron facility at Tokyo Institute of Technology and at the photon facility at AIST (Sanso-ken). Research opportunities in the future at RIBF, J-PARC, and SPRING8 are also discussed. A discussion on the research activities at CNS has been specifically extended in the latter half, including various possibilities in collaboration at the RI beam factory at RIKEN [ABSTRACT FROM AUTHOR]

The paper reports on the test of the newly developed RIKEN-ATOMKI CsI(Tl) array. It is demonstrated that high-quality detectors with excellent light collection efficiency and narrow resolution distribution could be produced. The setup has been commissioned in the study of the reaction of 22O + CD2. In the present paper, we summarize the results mainly on the (d, d′) channel. From the cross section for the transition between the ground state and the first 2+ state, we could deduce the "matter" deformation parameter to be βM=0.23±0.02 by distorted wave analysis. Comparing this data with previous measurements it can be concluded that 22O isotope has moderate and similar neutron and proton deformations. [ABSTRACT FROM AUTHOR]

Well-established data on production-rates of long-lived radionuclides are important for the understanding and calculation of various nucleosynthesis processes. However, lack of information exists for a list of nuclides as pointed out by nuclear-data requests. In addition, the search for supernova (SN)-produced radionuclides will give an improved insight into explosive scenarios. Accelerator mass spectrometry (AMS) represents a technique, which is capable to quantify such long-lived radionuclides using mass spectrometric methods. The potential of AMS is presented here as a powerful tool for probing nucleosynthesis. Applications of AMS are exemplified for a few specific cases: the detection of extraterrestrial radioactivity on Earth in terrestrial archives as a signature of nearby SN explosions, and the measurement of cross-sections, as an important ingredient for stellar as well as nuclear model calculations. [ABSTRACT FROM AUTHOR]

TACTIC (TACTIC web site: http://tactic.triumf.ca) is a new detector for low-energy nuclear reactions currently under development at TRIUMF. The cylindrical ionization chamber allows three-dimensional reconstruction of particle tracks by means of a two-dimensional anode array combined with a TOF measurement of the drift electrons. In addition, the integrated charge for each pulse provides information about the energy loss of the particle and therefore allows a better identification of the nuclear species producing the track. The geometry of TACTIC covers a large angular range permitting the measurement of differential cross-sections over a large solid angle. It will be ideal for investigations of nuclear processes pertinent to the field of nuclear astrophysics. [ABSTRACT FROM AUTHOR]

The structure of the neutron-rich nucleus 47Ar has been investigated through the d(46Ar,47Ar)p transfer reaction. The radioactive beam of 46Ar at 10 A · MeV was provided by the SPIRAL facility at GANIL. The protons corresponding to a neutron pick-up on bound or unbound states mechanism in 47Ar nuclei were detected at backward angles by the position-sensitive Si array-detector MUST. The transfer-like ejectiles were detected in the SPEG spectrometer. Level scheme, spin assignments and spectroscopic factors have been deduced for 47Ar and compared to shell model predictions. They suggest a slight erosion of the N=28 shell gap from the weakening of the spin-orbit interaction arising from the f and p orbitals. These spectroscopic information are subsequently used to infer (n, γ) reaction rates in the Ar isotopic chain to understand the origin of the 48Ca/46Ca abnormal isotopic ratio observed in certain inclusions of meteorites. [ABSTRACT FROM AUTHOR]

Conventionally, reaction rates relevant to nova nucleosynthesis are determined by performing the relevant proton capture reactions directly for stable species, or as has become possible more recently in inverse kinematics using short-lived accelerated radioactive beams with recoil separators. A secondary approach is to compile information on the properties of levels in the Gamow window using transfer reactions. We present a complementary technique where the states of interest are populated in a heavy-ion fusion reaction and their gamma decay studied with a state-of-the-art array of high-purity germanium detectors. The advantages of this approach, including the ability to determine resonance energies with high precision and the possibility of determining spins and parities from gamma-ray angular distributions are discussed. Two specific examples related to the 22Na(p, γ) and 30P(p, γ) reactions are presented. [ABSTRACT FROM AUTHOR]

The usual neutron-proton BCS wave function is simultaneously projected on both the good neutron and proton numbers using a discrete projection operator. The projected energy of the system is deduced as a limit of rapidly convergent sequence. It is numerically studied for the N=Z nuclei of which "experimental" pairing gaps may be deduced from the experimental odd-even mass differences. It then appears that the particle-number fluctuation effect is even more important than in the case of pairing between like-particles. [ABSTRACT FROM AUTHOR]

Experimental signatures of the dynamical correlations of a core with a single-particle neutron have been found in light neutron-rich nuclei investigated via the (7Li,7Be)c harge-exchange reactions at around 8MeV/u. Of particular astrophysical relevance are low-lying narrow resonances (Γ ∼ 200 keV FWHM) BSEC (Bound States Embedded in the Continuum). Because of their long lifetime BSEC states are likely to effect the capture rates in any scenario for nucleosynthesis in neutron-rich environment. They have been observed in the continuum of 11Be and 15C nuclei. A microscopic nuclear structure model based on QRPA theory, which takes into account Dynamical Core Polarisation (DCP) correlations, gives a suitable description of these resonances as well as single-particle states of the studied systems. In this context, high-energy narrow structures populated in nuclei having an integer number of α-particles plus three neutrons are good BSEC candidates and can be systematically investigated. [ABSTRACT FROM AUTHOR]

The relativistic invariant approach is applied to analyzing the 3.3 A GeV 22Ne fragmentation in a nuclear track emulsion. New results on few-body dissociations have been obtained from the emulsion exposures to 2.1 A GeV 14N and 1.2 A GeV 9Be nuclei. It can be asserted that the use of the invariant approach is an effective means of obtaining conclusions about the behavior of systems involving a few He nuclei at a relative energy close to 1 MeV per nucleon. The first observations of fragmentation of 1.2 A GeV 8B and 9C nuclei in emulsion are described. The presented results allow one to justify the development of few-body aspects of nuclear astrophysics. [ABSTRACT FROM AUTHOR]

The single-particle structure and shell gap of 100Sn as inferred from previous in-beam γ-ray spectroscopy has been confirmed in recent studies of seniority and spin-gap isomers by γγ, βγ, βpγ, pγ and 2pγ spectroscopy. The results for 94,95Ag, 98Cd and its N=50 isotones 96Pd and 94Ru stress the importance of large-scale shell model calculations employing realistic interactions for the isomerism, np-nh excitations, seniority mixing and E2 polarisation of the 100Sn core. The strong monopole interaction of the Δl=0, 1 spin/isospin-flip partners πg9/2-νg7/2 along the N=50 isotones and the πf5/2-νg9/2 pair of nucleons along the Z=28 Ni isotopes are decisive for the evolution of the shell structure towards 100Sn and 78Ni. It can be traced back to the tensor force in the effective nucleon-nucleon interaction and provides a straightforward explanation for new shells in neutron-rich light nuclei, implying qualitative predictions for new N=32, 34 subshells in Ca isotopes, persistence of the 78Ni proton and neutron shell gaps and non-equivalence of the g9/2 valence mirror Ni isotopes and N=50 isotones. This is corroborated by recent experimental data on 56,58Cr and 70-76Ni. The implication of monopole driven shell evolution for apparent spin-orbit splitting towards N ≫ Z and structure along the astrophysical r-path between N=50 and N=82 is discussed [ABSTRACT FROM AUTHOR]

We study the equation of state of strongly interacting matter at large densities and vanishing temperature. The hadronic matter equation of state is computed in a relativistic mean-field model and the quark matter equation of state is computed using a NJL-type model which takes into account the possibility of formation of the gapless color flavor locked phase. We focus in particular on the possible phase transition from hadronic matter to quark matter using both Maxwell and Gibbs constructions. We finally discuss the relevance of the equation of state in the context of compact stars and we propose some astrophysical signatures of the presence of quark matter in compact stars. [ABSTRACT FROM AUTHOR]

A simple approach is presented to estimate the position of the first opposite-parity state for p- and sd-shell nuclei. The approach is based on the assumption that the quadrupole-quadrupole interaction determines the energy of the lowest-lying states, and they are a mixture of a few leading SU(3) irreps even in the presence of further symmetry-breaking interactions. The quadrupole-quadrupole interaction together with the indirect effect of the Pauli exclusion principle will then lead to a rich structure in the trends of observables along Z, N and A chains. A comparison with the experimental data is given, with the carbon chain as illustrative example. The findings suggest that the changing shell structure near the neutron drip line might be explained by the appearance of low-lying highly deformed 2ħω states. [ABSTRACT FROM AUTHOR]

It has been realised recently that charge symmetry of the nucleon-nucleon interaction leads to a certain relation between Asymptotic Normalization Coefficients (ANCs) in mirror-conjugated one-nucleon overlap integrals. This relation can be approximated by a simple analytical formula that involves mirror neutron and proton separation energies, the core charge and the range of the strong nucleon-core interaction. We perform detailed microscopic multi-channel cluster model calculations and compare their predictions to the simple analytical formula as well as to calculations within a single-particle model in which mirror symmetry in potential wells and spectroscopic factors are assumed. The validity of the latter assumptions is verified on the basis of microscopic cluster model calculations. For mirror pairs in which one of the states is above the proton decay threshold, a link exists between the proton partial width and the ANC of the mirror neutron. This link is given by an approximate analytical formula similar to that for a bound-bound mirror pair. We compare predictions of this formula to the results of microscopic cluster model calculations. Mirror symmetry in ANCs can be used to predict cross sections for proton capture at stellar energies using neutron ANCs measured with stable or "less radioactive" beams. [ABSTRACT FROM AUTHOR]

The low-energy, bare-nucleus cross section for 15N(p, α)12C is extracted by means of the Trojan-Horse Method applied to the 2H(15N, α12C)n reaction at Ebeam = 60 MeV. The astrophysical S-factor is compared to the direct data in the same energy region. A nice agreement shows up down to 100 keV, while the low-energy behaviour of the S-factor suggests a smaller rate than is reported in the literature. [ABSTRACT FROM AUTHOR]

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 S17(0) = 18.7 ± 1.9 eV · b for the key reaction for solar neutrino production 7Be(p, γ)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, γ)23Al. [ABSTRACT FROM AUTHOR]

The Coulomb dissociation of 27P was studied experimentally using 27P beams at 57 MeV/nucleon with a lead target. The E2 gamma decay width of the first excited state in 27P was determined to be (2.8 ± 0.5) × 10−5 eV. The total (M1+E2)gamma decay width of the state, which is of astrophysical interest, is estimated by combining the experimental result and a shell model calculation. The reaction rate of 26Si(p, γ)27P is deduced from the estimated total gamma decay width. The astrophysical implication derived from estimated gamma decay width is discussed. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) was applied to the 3He+7Li interaction in order to investigate the quasi-free 7Li(p, α)4He reaction. The three-body experiment was performed at 33 MeV corresponding to a 7Li-p relative energy ranging from 50 keV to 7 MeV. The extracted 7Li(p, α)4He quasi-free cross-section was compared with the behavior of direct data, as well as with the result of a previous THM investigation on the 7Li(p, α)4He reaction off the neutron in 2H. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM. [ABSTRACT FROM AUTHOR]

In this paper we present first results from a 8Li electromagnetic neutron-breakup experiment. Specific reactions studied were Pb(8Li,7Li+n)Pb and C(8Li,7Li+n)C at 41 MeV/nucleon beam energy. This is an effort to compare the results of a Coulomb dissociation experiment with the well determined (n, γ) reaction cross sections at astrophysical energies. The angular dependence of the cross section above 7 degree, which is the grazing angle of 8Li-Pb system, is similar in shape for lead and carbon and approximately proportional to A2/3 in magnitude indicating that the nuclear dissociation is the main component in this region. At very forward angles the angular distributions differ significantly and the electromagnetic dissociation dominates for the lead, although the nuclear contribution is not negligible. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method has been applied to the 2H(9Be, 6Liα)n three-body reaction in order to investigate the 9Be(p, α)6Li two-body reaction, which is involved in the study of light element abundances (lithium, beryllium and boron). A coincidence measurement was performed in order to identify the presence of the quasi-free mechanism in the three-body reaction, needed for the application of the method. The astrophysical S(E)-factor was extracted and compared to direct data. No information about electron screening effects can be extracted due to the poor resolution of the indirect data. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work was performed to understand the structure of neutron-rich fission fragments around the 130 mass region. A thin 235U target was bombarded by a 14N beam with 10 MeV/A from the Separated Sector Cyclotron at the iThemba Laboratory for Accelerator Based Sciences, Cape Town, South Africa. The main goal was to detect and identify fission fragments and to obtain their mass distribution by using solar cell detectors in the AFRODITE (African Omnipurpose Detector for Innovative Techniques and Experiments) spectrometer. The X-rays emitted from fission fragments were detected by LEP (Low Energy Photon) detectors and γ-rays emitted from excited states of the fission fragments were detected by CLOVER detectors in the spectrometer. [ABSTRACT FROM AUTHOR]

The elastic scattering cross section of 106Cd(α, α)106Cd has been measured with high accuracy at energies of Ec.m. ≈ 15.5, 17, and 19MeV. The optical potential for the system 106Cd ⊗α has been derived at energies above and below the Coulomb barrier. Predictions for the 106Cd(α, γ)110Sn capture cross section at astrophysically relevant energies are presented and compared to the experimental data measured recently. [ABSTRACT FROM AUTHOR]

Owing to the presence of the Coulomb barrier at astrophysically relevant kinetic energies it is very difficult, or sometimes impossible, to measure astrophysical reaction rates in the laboratory. That is why different indirect techniques are being used along with direct measurements. Here we address two important indirect techniques, the asymptotic normalization coefficient (ANC) and the Trojan Horse (TH) methods. We discuss the application of the ANC technique for calculation of the astrophysical processes in the presence of subthreshold bound states, in particular, two different mechanisms are discussed: direct capture to the subthreshold state and capture to the low-lying bound states through the subthreshold state, which plays the role of the subthreshold resonance. The ANC technique can also be used to determine the interference sign of the resonant and nonresonant (direct) terms of the reaction amplitude. The TH method is unique indirect technique allowing one to measure astrophysical rearrangement reactions down to astrophysically relevant energies.We explain why there is no Coulomb barrier in the sub-process amplitudes extracted from the TH reaction. The expressions for the TH amplitude for direct and resonant cases are presented. [ABSTRACT FROM AUTHOR]

7Be decays via electron capture and therefore its half-life is expected to depend on the electron density at the nucleus. We measured the 7Be half-life in palladium, tungsten, zirconium and tantalum metals, in order to investigate the influence of the quasi-free electrons in metals on the probability of electron capture. The 7Be samples were obtained implanting a 4.85MeV pure radioactive 7Be ion beam. The 7Be half-life was determined measuring the 478 keV gamma decay following the electron capture by means of HPGe detectors. In order to reduce systematic errors, we planned to perform independent measurements in three different laboratories: Naples (Italy), Bochum (Germany) and Debrecen (Hungary). On the basis of the first results, we do not find a 7Be half-life change within the experimental errors of 0.4%. [ABSTRACT FROM AUTHOR]