A resonance observed in the excitation function of the ${}^{12}\mathrm{C}{+}^{12}{\overrightarrow{\mathrm{C}}}^8{\mathrm{Be}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}{+}^{16}{\mathrm{O}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}\alpha$-transfer reaction around $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=32.5\mathrm{}$ MeV is studied by the method of coupled-channel Born approximation (CCBA), in which the distorted waves are given by the microscopic coupled-channel (CC) calculations and the $\alpha$-transfer reaction processes are treated as the one-step transitions. The CCBA calculation reproduces well the characteristic behavior of the excitation function as well as the angular distribution at the on-resonance energy. The result of the analysis suggests that the $(\alpha +\alpha )+\left(\alpha {+}^{12}\mathrm{C}\right)$ type four-cluster states are populated in this reaction.

An attempt was made to find the very neutron-rich isotope ${}^{21}\mathrm{B}$ among the fragmentation of a $94A\mathrm{MeV}$ ${}^{40}\mathrm{Ar}$ beam. Evidence for the particle instability of ${}^{21}\mathrm{B}$ was obtained. As part of the search, the production cross sections of 13 light neutron-rich nuclei with Be and Ta targets are presented and compared to previous data. A large enhancement of the production cross sections for a Ta target is shown and a clear energy dependence of the production cross sections is shown for very neutron-rich nuclei.

We explore the possibility of measurements of Hanbury Brown–Twiss correlations in $\gamma \gamma$ channels in the high multiplicity environment of heavy ion collisions. We consider all possible sources of photon-photon correlations and show that one can separate correlations of photons produced directly in the hot zone and residual correlations of decay photons: the former contribute to the region of small invariant relative momentum $q_{\mathrm{inv}}\lesssim 50$ MeV, while the latter contribute to larger relative momentum and, negligibly, to the small $q_{\mathrm{inv}}$ region. We make predictions of the photon correlation functions at SPS and RHIC energies.

Several hadronic observables have been studied in central $158A\hspace{0.5em}\mathrm{GeV}$ Pb+Pb collisions using data measured by the WA98 experiment at CERN: single ${\pi }^{-}$ and $K^{-}$ production, as well as two- and three-pion interferometry. The Wiedemann-Heinz hydrodynamical model has been fitted to the pion spectrum, giving an estimate of the temperature and transverse flow velocity. Bose-Einstein correlations between two identified ${\pi }^{-}$ have been analyzed as a function of $k_T,$ using two different parametrizations. The results indicate that the source does not have a strictly boost invariant expansion or spend time in a long-lived intermediate phase. A comparison between data and a hydrodynamical based simulation shows very good agreement for the radii parameters as a function of $k_T.$ The pion phase-space density at freeze-out has been measured, and agrees well with the Tomás̆ik-Heinz model. A large pion chemical potential close to the condensation limit of $m_{\pi }$ seems to be excluded. The three-pion Bose-Einstein interferometry shows a substantial contribution of the genuine three-pion correlation, but not quite as large as expected for a fully chaotic and symmetric source.

We study $J/\psi$ suppression in Pb+Pb collisions at CERN-SPS energies in hadronic matter with energy- and temperature-dependent charmonium dissociation cross sections calculated in the quark-interchange model of Barnes and Swanson. The charmonium dissociation cross sections depend sensitively on energy and increase significantly as temperature increases. We find that the variation of $J/\psi$ survival probability from peripheral to central collisions can be explained as induced by hadronic matter absorption in central collisions.

We apply the chiral SU(3) quark mean field model to investigate strange quark matter. The stability of strange quark matter with a different strangeness fraction is studied. The interaction between quarks and vector mesons destabilizes the strange quark matter. If the strength of the vector coupling is the same as in hadronic matter, strangelets cannot be formed. For the case of $\beta$ equilibrium, there is no strange quark matter that can be stable against hadron emission even without vector meson interactions.

${\Lambda }_c^{+}$ and ${\Lambda }_b$ hypernuclei are studied in the quark-meson coupling (QMC) model. Comparisons are made with the results for $\Lambda$ hypernuclei studied in the same model previously. Although the scalar and vector potentials felt by the $\Lambda ,$ ${\Lambda }_c^{+},$ and ${\Lambda }_b$ in the corresponding hypernuclei multiplet which has the same baryon numbers are quite similar, the wave functions obtained, e.g., for the ${1s}_{1/2}$ state, are very different. The ${\Lambda }_c^{+}$ baryon density distribution in ${}_{{\Lambda }_c^{+}}^{209}\mathrm{Pb}$ is much more pushed away from the center than that for the $\Lambda$ in ${}_{\Lambda }^{209}\mathrm{Pb}$ due to the Coulomb force. On the contrary, the ${\Lambda }_b$ baryon density distributions in ${\Lambda }_b$ hypernuclei are much larger near the origin than those for the $\Lambda$ in the corresponding $\Lambda$ hypernuclei due to its heavy mass. It is also found that level spacing for the ${\Lambda }_b$ single-particle energies is much smaller than that for the $\Lambda$ and ${\Lambda }_c^{+}.$

New measurements of the photoneutron reaction on ${}^{181}\mathrm{Ta}$ have been conducted with the AIST-LCS (laser Compton scattering) beam in the $7.8\lesssim E\left[\mathrm{MeV}\right]\lesssim 12$ energy range. The major advantage of the present $\gamma$-ray experiment is its intense peaking in the energy window of astrophysical interest, i.e., close to the neutron threshold. Details on photon beams from the laser Compton scattering, neutron counting, and experimental determination of the ${}^{181}\mathrm{Ta}$ photoneutron cross section are given. The present experimental data are in good agreement with the IAEA evaluation. Reaction rate calculations in the Hauser-Feshbach statistical model are performed and confronted with the experimental data. The data provide constraints on the low-energy tail of the dipole strength function. It is found that among the three different models for the $E1\mathrm{}$-strength considered, only the microscopic quasiparticle random phase approximation model can reproduce the extra strength observed in the ${}^{181}\mathrm{Ta}(\gamma {,n)}^{180}\mathrm{Ta}$ reaction at energies of about 8.5 MeV. Such an experiment helps to improve the determination of the corresponding stellar photodisintegration rate of ${}^{181}\mathrm{Ta}$ which directly influences the p-process production of ${}^{180}\mathrm{Ta}.$

The long-wavelength approximation and the truncated Taylor expansion are frequently used in the theory of relativistic Coulomb excitation to obtain multipole expansions of the interaction. It is shown in this Brief Report that these two approximations are exactly equivalent.

Anisotropic flow of protons and negative pions in $4.2A\mathrm{GeV}/c$ $\mathrm{C}+\mathrm{Ta}$ collisions is studied using the Fourier analysis of azimuthal distributions. The protons exhibit pronounced directed flow. Directed flow of pions is positive in the entire rapidity interval and indicates that the pions are preferentially emitted in the reaction plane from the target to the projectile. The elliptic flow of protons and negative pions is close to zero. Comparison with the quark-gluon-string model and relativistic transport model show that they both yield a flow signature similar to the experimental data.

We have developed models of the fission barrier (barrier heights and transition state spectra) that reproduce reasonably well the measured fission cross section of ${}^{235}\mathrm{U}$ from a neutron energy of from 1 keV to 2 MeV. From these models we have calculated the fission cross section of the 77 eV isomer of ${}^{235}\mathrm{U}$ over the same energy range. We find that the ratio of the isomer cross section to that of the ground state lies between about 0.45 and 0.55 at low neutron energies. The cross sections become approximately equal above 1 MeV. The ratio of the neutron capture cross section to the fission cross section for the isomer is predicted to be about a factor of 3 larger for the isomer than for the ground state of ${}^{235}\mathrm{U}$ at keV neutron energies. We have also calculated the cross section for the population of the isomer by inelastic neutron scattering from the ${}^{235}\mathrm{U}$ ground state. We find that the isomer is strongly populated, and for $E_n=1\mathrm{}$ MeV the ${(n,n}^{\prime }\gamma )$ cross section leading to the population of the isomer is of the order of 0.5 b. Thus, neutron reaction network calculations involving the uranium isotopes in a high neutron fluence are likely to be affected by the 77 eV isomer of ${}^{235}\mathrm{U}.$ With these same models the fission cross sections of ${}^{233}\mathrm{U}$ and ${}^{237}\mathrm{U}$ can be reproduced approximately using only minor adjustments to the barrier heights. With the significant lowering of the outer barrier that is expected the general behavior of the fission cross section of ${}^{239}\mathrm{Pu}$ can also be reproduced.

Two approaches for the analysis of pion photoproduction and electroproduction on nucleons in the resonance energy region are checked at $Q^2=0\mathrm{}$ using the results of the GWU(VPI) partial-wave analysis of photoproduction data. The approaches are based on dispersion relations and the unitary isobar model. Within dispersion relations a good description of photoproduction multipoles is obtained up to $W=1.8\mathrm{}\mathrm{GeV}.$ Within the unitary isobar model, modified with increasing energy by the incorporation of Regge poles and with a unified Breit-Wigner parametrization of resonance contributions, a good description of photoproduction multipoles is obtained up to $W=2\mathrm{}\mathrm{GeV}.$

The periodic solutions previously considered for nuclear time-dependent Hartree-Fock problems are recalculated by a new method which is more accurate and reliable. It starts from a first guess of the entire periodic trajectory, instead of a first guess of the initial state. An exact solution of the discretized nonlinear equations is then obtained in three to five iterations involving, once again, the entire trajectory. The resulting families of solutions, and in particular the relationship between the period and the energy, are much more complicated than previously thought. The meaning of this outcome is discussed.

The wobbling excitations in the presence of an appreciable amount of alignment are expected to appear more easily at lower angular momenta of the yrast spectra, compared with those in the textbook example. The large $B(E2;\overrightarrow{I}I-1)$ value for $\Delta \mathrm{n̂}=1\mathrm{}$ transitions where $\mathrm{n̂}$ expresses the number of wobbling phonons is shown to be a strongly increasing function of the triaxiality parameter $\gamma ,$ especially for $\gamma \gtrsim +20\mathrm{}°,$ while it is relatively independent of moments of inertia. On the other hand, the relation of the wobbling phonon energy to the total angular momentum may be used to extract quantitative information on nuclear moments of inertia. It is concluded that the $\gamma$ value of the triaxial, strongly deformed bands in ${}^{163}\mathrm{Lu}$ is about equal to $+20\mathrm{}°$ and may be slightly increasing as a function of I.

We study pion-nucleon scattering with a chiral Lagrangian of pions, nucleons, and $\Delta$ isobars to order $Q^3,$ where Q is a generic small momentum. We compare the results from heavy baryon chiral perturbation theory with those from the infrared regularization scheme. While the former provides a reasonable fit to the data out to a pion c.m. kinetic energy of 100 MeV, the latter is only able to fit up to 40 MeV and even then the parameters obtained are unreasonable. Difficulties with the infrared scheme in the u channel are discussed.

Beta-decay properties of the neutron drip-line nuclei ${}^{19}\mathrm{B},{}^{22}\mathrm{C},$ and ${}^{23}\mathrm{N}$ have been studied using projectile fragments from 95 MeV/nucleon ${}^{40}\mathrm{Ar}$ ions incident on a ${}^{\mathrm{nat}}\mathrm{Ta}$ target. The $\beta$-decay half-lives of ${}^{22}\mathrm{C}$ and ${}^{23}\mathrm{N}$ have been determined for the first time to be ${6.1}_{-1.2}^{+1.4\mathrm{}}$ and ${14.1}_{-1.5}^{+1.2\mathrm{}}$ ms, respectively. The half-life of ${}^{19}\mathrm{B}$ was reinvestigated, resulting in a new value of $2.92\pm 0.13$ ms. The $\beta$-delayed neutron multiplicities have also been determined to be $P_{1n}{=71.8\mathrm{}}_{-9.1}^{+8.3\mathrm{}}\%,P_{2n}{=16.0\mathrm{}}_{-4.8}^{+5.6\mathrm{}}\%$ for ${}^{19}\mathrm{B},P_{1n}{=61\mathrm{}}_{-13}^{+14\mathrm{}}\%$ for ${}^{22}\mathrm{C},$ and $P_{1n}{=42.2\mathrm{}}_{-6.5}^{+6.3\mathrm{}}\%,P_{2n}{=8.0\mathrm{}}_{-3.4}^{+3.8\mathrm{}}\%$ for ${}^{23}\mathrm{N}.$ The results are compared with theoretical predictions.

Twenty-one $\gamma$ transitions in ${}^{93}\mathrm{Sr}$ were identified from $\gamma -\gamma -\gamma$ coincidences in the spontaneous fission of ${}^{252}\mathrm{Cf}$ starting with the previously known three transitions in ${}^{93}\mathrm{Sr}.$ The level structure of this nucleus is interpreted in part as arising from the weak coupling of the ${1d}_{5/2}$ neutron hole to the yrast states of the ${}^{94}\mathrm{Sr}$ core. We have tried to give a quantitative description of the properties of ${}^{93}\mathrm{Sr}$ by performing a shell-model study in which we assume that ${}^{88}\mathrm{Sr}$ is a closed core. In this study we have also considered the neighboring isotopes ${}^{90,92,94}\mathrm{Sr}.$ The calculated spectra have been compared with the experimental data.

Final-state interactions in the response of a many-body system to an external probe delivering large momentum are normally described using the eikonal approximation, for the trajectory of the struck particle, and the frozen approximation, for the positions of the spectators. We propose a generalization of this scheme, in which the initial momentum of the struck particle is explicitly taken into account. Numerical calculations of the nuclear matter response at $1<\mathrm{}|\mathbf{q}|<2\mathrm{}\mathrm{GeV}/c$ show that the inclusion of this momentum dependence leads to a sizable effect in the low-energy tail. Possible implications for the analysis of existing electron-nucleus scattering data are discussed.

An absorbing boundary condition approach to nuclear breakup reactions is investigated. A key ingredient of the method is an absorbing potential outside the physical area, which simulates the outgoing boundary condition for scattered waves. After discretizing the radial variables, the problem results in a linear algebraic equation with a sparse coefficient matrix, to which efficient iterative methods can be applicable. No virtual state such as a discretized continuum channel needs to be introduced in the method. Basic aspects of the method are discussed by considering a nuclear two-body scattering problem described with an optical potential. We then apply the method to the breakup reactions of deuterons described in a three-body direct reaction model. Results employing the absorbing boundary condition are found to accurately coincide with those of the existing method which utilizes discretized continuum channels.