To study the α-cluster states in the ${}^{38}\mathrm{Ar}$ nucleus, angular correlation functions between t and α in the ${}^{34}\mathrm{S}$(${}^7\mathrm{Li}$, $t\alpha$)${}^{38}\mathrm{Ar}$ reaction have been measured. Seven states at 10.2, 10.8, 11.4, 12.2, 12.7, 14.3, and 15.0 MeV were newly observed.

A recent measurement of direct α-particle emission from the ${}^{238}\mathrm{U}$(${}^6\mathrm{He}$, fission) reaction is shown to be strongly influenced by the fission trigger.

This paper was published online on 20 May 2005 without several of the authors’ corrections incorporated. Equation (13) has been replaced. The captions of Figs. 16–18 have also been replaced. Typographical errors on pages 4, 6, 14, 15, 18, 19, 22, and 24 have all been corrected. The paper has been corrected as of 8 June 2005. The text is correct in the printed version of the journal.

The di-trinucleon clustering resonances of ${}^3\mathrm{He}+{}^3\mathrm{He}$ in ${}^6\mathrm{Be}$ and $t+t$ in ${}^6\mathrm{He}$ were studied via the ${}^6\mathrm{Li}({}^3\mathrm{He},t{}^3\mathrm{He})$ and ${}^6\mathrm{Li}({}^7\mathrm{Li},{}^7\mathrm{Be}t)$ reactions at incident energies of 450 and 455 MeV, respectively. A new resonance in ${}^6\mathrm{Be}$ was found at $E_x=18.0\pm 1.2\text{MeV}$ with a width of $9.2\pm 1.0\text{MeV}$ in the binary decay channel of ${}^6\mathrm{Be}\to {}^3\mathrm{He}+{}^3\mathrm{He}$. The resonance in ${}^6\mathrm{He}$ previously reported was also observed at $E_x=18.0\pm 1.0\text{MeV}$ with a width of $9.5\pm 1.0\text{MeV}$ in the binary decay channel of ${}^6\mathrm{He}\to t+t$. The branching ratios of the resonances for each binary decay were both $0.7\pm 1.0$, which was larger than the branching ratio calculated in a statistical model by two orders of magnitude. The angular correlations measured for t and ${}^3\mathrm{He}$ particles in the binary decay show a contribution dominantly from the multipolarity of $L=1$. We suggest that the resonances are the members of the isobaric triplet of the ${}^{3}P$ resonances in $A=6$ nuclei.

We investigate the thermalization of charm quarks in high-energy heavy-ion collisions. To this end, we calculate the diffusion coefficient in the perturbative quark gluon plasma and relate it to collisional energy loss and momentum broadening. We then use these transport properties to formulate a Langevin model for the evolution of the heavy quark spectrum in the hot medium. The model is strictly valid in the nonrelativistic limit and for all velocities $\gamma v<\alpha s^{-1/2}$ to leading logarithm in $T/m_D$. The corresponding Fokker-Planck equation can be solved analytically for a Bjorken expansion and the solution gives a simple estimate for the medium modifications of the heavy quark spectrum as a function of the diffusion coefficient. Finally we solve the Langevin equations numerically in a hydrodynamic simulation of the heavy-ion reaction. The results of this simulation are the medium modifications of the charm spectrum $R_{\mathit{AA}}$ and the expected elliptic flow $v_2(p_T)$ as a function of the diffusion coefficient.

We calculate the width of the ${\Theta }^{+}(1540)$ pentaquark in a relativistic model in which the pentaquark is considered to be composed of a scalar diquark and a spin 1/2 triquark. We consider both positive and negative parity for the pentaquark. There is a single parameter in our model which we vary and which describes the size of the pentaquark. If the pentaquark size is somewhat smaller than that of the nucleon, we find quite small widths for the pentaquark of about 1 MeV or less. Our model of confinement plays an important role in our analysis and makes it possible to use Feynman diagrams to describe the decay of the pentaquark.

We have studied the residual interaction effects theoretically on the deeply bound pionic states in Pb and Sn isotopes. We need to evaluate the residual interaction effects carefully to deduce the nuclear medium effects for pion properties, which are believed to provide valuable information on nuclear chiral dynamics. The s- and p-wave $\pi N$ interactions are used for the pion-nucleon residual interactions. We show that the complex energy shifts are around [(10–20) + i(2–7)] keV for $1s$ states in Sn, which should be taken into account in the analyses of the high precision data of deeply bound pionic $1s$ states in Sn isotopes.

The presence of isospin mixing in the $T=5/2$ ground state of ${}^{71}\mathrm{As}$ was studied via anisotropic positron emission from oriented nuclei. A small isospin-forbidden Fermi component in the predominantly Gamow-Teller β decay was established, corresponding to an isospin mixing probability of $(13\pm 4)\times {10}^{-6}$. The sign of the magnetic moment of ${}^{71}\mathrm{As}$ was determined to be positive.

The $\alpha +2n$ and $t+t$ clustering of the ${}^6\mathrm{He}$ ground state were investigated by means of the transfer reaction ${}^6\mathrm{He}(p,t){}^4\mathrm{He}$ at 25 MeV/nucleon. The experiment was performed in inverse kinematics at GANIL with the SPEG spectrometer coupled to the MUST array. Experimental data for the transfer reaction were analyzed by a distorted wave Born approximation (DWBA) calculation, including the two neutrons and the triton transfer. The couplings to the ${}^6\mathrm{He}\to {}^4\mathrm{He}+2n$ breakup channels were taken into account with a polarization potential deduced from a coupled-discretized-continuum channels analysis of the ${}^6\mathrm{He}+{}^1\mathrm{H}$ elastic scattering measured at the same time. The influence on the calculations of the $\alpha +t$ exit potential and of the triton sequential transfer is discussed. The final calculation gives a spectroscopic factor close to one for the $\alpha +2n$ configuration as expected. The spectroscopic factor obtained for the $t+t$ configuration is much smaller than the theoretical predictions.

The level structures of the $N=50$ ${}^{85}\mathrm{Br}$ and ${}^{87}\mathrm{Rb}$ isotopes have been studied in the fission of the compound system formed in three different heavy-ion-induced reactions. In ${}^{87}\mathrm{Rb}$ many states above the previously known 9/2${}^{+}$ isomer have been established. The coupling of the odd proton occupying the $g_{9/2}$ orbital to the yrast states in the ${}^{86}\mathrm{Kr}$ core can account for the first excited states above the isomer in ${}^{87}\mathrm{Rb}$. A comparison with the first excited states above the 9/2${}^{+}$ state in ${}^{85}\mathrm{Kr}$ and ${}^{89}\mathrm{Y}$ reveals similarities in the coupling. At higher excitations similar behavior to ${}^{89}\mathrm{Y}$ is observed, indicating a possible presence of neutron-core excitations. In ${}^{85}\mathrm{Br}$ several states up to ~5 MeV excitation energy have been established. Two states at ~2 MeV excitation energy are candidates for the 9/2${}^{+}$ state originating from the odd proton occupying the $g_{9/2}$ orbital. The experimental results for both isotopes are compared with predictions of the shell model.

Angular correlations and cross sections for the ${}^{40}\mathrm{Ca}(e,e^{\text{'}}n){}^{39}\mathrm{Ca}$ reaction have been measured in the continuum above the giant resonance. A comparison of the missing energy spectra between the peak and the tail regions of the giant resonance indicates that neutron emission in the peak region leads to populating the ground and first excited states, whereas emission in the tail region leads to populating excited states at an energy about 4.5 MeV higher. The latter seems to be because of the $2s_{1/2}$ and $1d_{5/2}$ hole excitation, that is core excitation. The same tendency was observed in the ${}^{28}\mathrm{Si}(e,e^{\text{'}}n){}^{27}\mathrm{Si}$ reaction of the sd shell nuclei but it did not appear as clearly in the ${}^{12}\mathrm{C}(e,e^{\text{'}}n){}^{11}\mathrm{C}$ reaction of the 1p shell nuclei.

The level structure of ${}^{197}\mathrm{Au}$ has been studied using the ($n,n^{\text{'}}\gamma$) reaction. A germanium detector array (GEANIE) for γ-ray detection and the “white” neutron source at LANSCE/WNR were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Partial γ-ray cross sections were measured for a total of 90 transitions of ${}^{197}\mathrm{Au}$. A total of 52 new γ rays were assigned to ${}^{197}\mathrm{Au}$ and placed on the level scheme based on the partial γ-ray excitation functions and the $\gamma \text{−}\gamma$ coincidence data. The level scheme of ${}^{197}\mathrm{Au}$ is now more complete up to ~2 MeV excitation energy. The first excited states of the decoupled band built on the proton-hole $h_{11/2}$ configuration were established.

A high resolution measurement of the cross sections of the ${}^{44}\mathrm{Ca}$($p,p_0$) and ${}^{44}\mathrm{Ca}$($p,p_1$) reactions was performed over the energy range $E_p=2.50\text{−}3.53\mathrm{MeV}$. A total of 809 resonances were observed. The purity and completeness of the ${}^{45}\mathrm{Sc}$ data were tested with a variety of statistical analyses. These analyses suggest that the $1/2^{+}$ and $1/2^{-}$ resonance sequences are the most pure and complete ever measured. The resulting level densities are $\rho (1/2){}^{+}={127}_{-8}^{+7}{\mathrm{MeV}}^{-1}$ and $\rho (1/2^{-})={132}_{-9}^{+8}{\mathrm{MeV}}^{-1}$; there is no evidence of parity dependence of the level density of $J=1/2$ states at $E_x=10$ MeV in ${}^{45}\mathrm{Sc}$.

Some properties of fast, nonequilibrium splitting of projectiles in the ${}^{124}\mathrm{Sn}+{}^{64}\mathrm{Ni}$ reaction at 35A MeV were determined using the $4\pi$ CHIMERA detector system. In particular the charge distributions, in- and out-of-plane angular distributions, and relative velocities of projectilelike fragments were measured. The time scale of the process was estimated and it turned out that the process is sequential but much faster than the ordinary, equilibrated fission.

We study the isospin dynamics in fragment formation within the framework of an analytical model based on the spinodal decomposition scenario. We calculate the probability to obtain fragments with given charge and neutron number, focussing on the derivation of the width of the isotopic distributions. Within our approach this is determined by the dispersion of $N/Z$ among the leading unstable modes, due to the competition between Coulomb and symmetry energy effects, and by isovectorlike fluctuations present in the matter that undergoes the spinodal decomposition. Hence the widths exhibit a clear dependence on the properties of the equation of state. By comparing two systems with different values of the charge asymmetry we find that the isotopic distributions reproduce an isoscaling relationship.

In neutrino phenomenology, terms in the oscillation probabilities linear in $\sin {\theta }_{13}$ lead naturally to the question “How can one measure ${\theta }_{13}$ including its sign?” Here we demonstrate analytically and with a simulation of neutrino data that ${\mathcal{P}}_{e\mu }$ and ${\mathcal{P}}_{\mu \mu }$ at $L/E=2\pi /{\Delta }_{21}$ exhibit significant linear dependence on ${\theta }_{13}$ in the limit of vacuum oscillations. Measurements at this particular value of $L/E$ can thus determine not only ${\theta }_{13}$ but also its sign, if CP violation is small.

The clustering phenomenon in light, stable and exotic nuclei is studied within the relativistic mean field (RMF) approach. Numerical calculations are done by using the axially deformed harmonic oscillator basis. The calculated nucleon density distributions and deformation parameters are analyzed to look for the cluster configurations. The calculations explain many of the well-established cluster structures in both the ground and intrinsic excited states. Comparisons of our results with other model calculations and the available experimental information suggest that the RMF theory is well suited for studying clustering in light nuclei. A few discrepancies and their possible sources are also discussed.

An analytic collective model in which the relative presence of the quadrupole and octupole deformations is determined by a parameter (${\varphi }_0$), while axial symmetry is obeyed, is developed. The model [to be called the analytic quadrupole octupole axially symmetric model (AQOA)] involves an infinite well potential, provides predictions for energy and $B(\mathit{EL})$ ratios, which depend only on ${\varphi }_0$, draws the border between the regions of octupole deformation and octupole vibrations in an essentially parameter-independent way, and describes well ${}^{226}\mathrm{Th}$ and ${}^{226}\mathrm{Ra}$, for which experimental energy data are shown to suggest that they lie close to this border. The similarity of the AQOA results with ${\varphi }_0={45}^{°}$ for ground-state band spectra and $B(E2)$ transition rates to the predictions of the X(5) model is pointed out. Analytic solutions are also obtained for Davidson potentials of the form ${\beta }^2+{\beta }_0^4/{\beta }^2$, leading to the AQOA spectrum through a variational procedure.

In this paper we study the process of fragmentation of highly excited Lennard-Jones drops by studying the emission of stable fragments (clusters recognizable in configuration space that live more than a minimum lifetime). We focus on the dynamics and thermodynamics of the emitting sources and show, among other things, that this kind of process is a mixture of sequential and simultaneous events and that simultaneous events have a broad time distribution. We also show how a local equilibrium scenario comes up on top of expanding collective motion, allowing us to define and explore a local temperature, which turns out to be a strongly time-dependent quantity, signaling that we are facing an out-of-equilibrium process.

The production of α particles in the ${}^7\mathrm{Li}+{}^{28}\mathrm{Si}$ reaction was studied at near-barrier energies. Angular distributions were measured at four energies, namely 9, 10, 11, and 13 MeV. The data were treated in a statistical model and DWBA framework to disentangle the degree of competition between direct and compound channels in the reaction and its energy evolution near the barrier. It was found that whereas the compound mechanism is substantial, d transfer and possibly t transfer are the dominant mechanism at near-barrier energies. The influence of the reaction channels on the optical potential threshold anomaly is discussed.