Two strongly coupled bands with large dynamic moment of inertia values have been observed for the first time in the neutron-deficient odd-odd nucleus ${}^{130}$Pr using Gammasphere and the Microball charged-particle detector array. These bands involve the important $g_{9/2}$[404]9/2 proton orbital. This new information on ${}^{130}$Pr coupled with Projected Shell Model calculations provide valuable insight on rotational alignment processes taking place in this mass region, the size of the $N$=72 deformed shell gap, and the position of the $i_{13/2}$[660]1/2 neutron intruder orbital at the boundary of the $A$=135 superdeformed region.

The contribution of the two-step process $\gamma d\to \mathrm{pn}\to {\pi }^{0}d$ to the imaginary part of the amplitude for coherent pion production on the deuteron is calculated at threshold exploiting unitarity constraints. The result shows that this absorptive process is not negligible and has to be considered in an extraction of the elementary neutron production amplitude from the $\gamma d\to {\pi }^{0}d$ cross section at threshold.

The nuclear response to longitudinally polarized electrons, detected in coincidence with out-of-plane high-energy protons, is discussed in a simple model where the ejectile wave function is approximated as a plane wave with a complex wave vector. This choice is equivalent to solving the problem of final-state interactions (FSI) in homogeneous nuclear matter, as the residual nucleus can be described to a first approximation when dealing with very fast emitted protons. The main advantage of the present method is that in the framework of the distorted-wave impulse approximation at the one-photon exchange level it allows for an analytical derivation of all the components of the nuclear response, including the so-called fifth structure function $f_{01}^{\prime }$, which is very sensitive to FSI. The imaginary part of the complex wave vector produces purely geometrical FSI effects and, consequently, breaks the symmetry of the cross section with respect to the incoming electron helicity. Inspection of every single contribution in the analytical formulas, here considered up to the fourth order in the nonrelativistic reduction in powers of the inverse nucleon mass, allows for a detailed study of the role of each elementary reaction mechanism. In particular, cancellations among the leading contributions determine the very small absolute size of $f_{01}^{\prime }$ and produce a nontrivial asymptotic scaling of the related helicity asymmetry for large values of the momentum transfer.

The excitation of a quantum gas of 112 independent fermions in the time-dependent potential well, periodically oscillating around the spherical shape, was followed over ten oscillation cycles. Five different oscillation frequencies are considered for each of the five types of deformations: spheroidal and Legendre polynomial ripples $P_3$, $P_4$, $P_5$, and $P_6$. The excitation rate of the gas in the deforming hard-walled cavities substantially decreases after initial one or two cycles and the final excitation energy is a few times smaller than the wall formula predictions. Qualitatively similar results are obtained for the diffused Woods-Saxon well. The details and possible origins of this behavior are discussed as well as the consequences for the one-body dissipation model of nuclear dynamics.

Within a complex free-energy density functional, derived from a realistic nucleon-nucleon interaction, the dependence on temperature of the real and imaginary parts of the free interaction energy of the deformed system U-U is investigated. It is found that the potentials strongly depend on orientations and temperature, where at zero orientation angle $(\beta =0\mathrm{}°)$ the potentials acquire repulsion, with increasing temperature, up to a critical value $\left(T\sim 3\mathrm{MeV}\right),$ where shell effects become very small; beyond this value the potentials inverse this behavior. For large values of β the potentials become more and more attractive with increasing temperature. At much higher excitation $\left(T\sim 5\mathrm{MeV}\right)$ the potentials become insensitive to orientations, due to the disappearance of shell corrections. The dependence of the relative momentum per nucleon on the internuclear distance is also investigated.

We reconsider the importance of statistical fluctuations for fission dynamics beyond the saddle in the light of recent evaluations of transport coefficients for average motion. The size of these fluctuations are estimated by means of the Kramers-Ingold solution for the inverted oscillator, which allows for an inclusion of quantum effects.

A phenomenological schematic model of multipole giant resonances (GR’s) is considered which treats the external interaction via common decay channels on the same footing as the coherent part of the internal residual interaction. The damping due to the coupling to the sea of complicated states is neglected. As a result, the formation of GR is governed by the interplay and competition of two kinds of collectivity, the internal and the external one. The mixing of the doorway components of a GR due to the external interaction significantly influences their multipole strengths, widths, and positions in energy. In particular, a narrow resonance state with an appreciable multipole strength is formed when the doorway components strongly overlap.

The mixing of the doorway components of a giant resonance (GR) due to the interaction via common decay channels influences significantly the distribution of the multipole strength and the energy spectrum of the decay products of the GR. The concept of the partial widths of a GR becomes ambiguous when the mixing is strong. In this case, the partial widths determined in terms of the $K$ and $S$ matrices must be distinguished. The photoemission turns out to be most sensitive to the overlapping of the doorway states. At high excitation energies, the interference between the doorway states leads to a restructuring towards lower energies and apparent quenching of the dipole strength.

Neutrons produced in the ${}^{40}$Ca+H reaction at $E_{\mathrm{lab}}=357A$ and $565A$ MeV have been detected using a three-module version of the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range around the beam in the forward direction $\left(0\mathrm{}°-3.2°\right)$. Semi-inclusive neutron production cross sections, at the two energies, are reported together with neutron energy spectra, angular, rapidity, and transverse momentum distributions. Comparison with a Boltzmann-Nordheim-Vlasov approach + phase space coalescence model is discussed.

We investigate the chemical equilibration of the parton distributions in collisions of two heavy nuclei. We use initial conditions obtained from a self-screened parton cascade calculation and, for comparison, from the HIJING model. We consider a one-dimensional as well as a three-dimensional expansion of the parton plasma and find that the onset of the transverse expansion impedes the chemical equilibration. At energies of 100 GeV/nucleon, the results for one-dimensional and three-dimensional expansions are quite similar except at large values of the transverse radius. At energies of several TeV/nucleon, the plasma initially approaches chemical equilibrium, but then is driven away from it, when the transverse velocity gradients develop. We find that the total parton multiplicity density remains essentially unaffected by the flow, but the individual concentrations of quarks, antiquarks, and gluons are sensitive to the transverse flow. The consequences of the flow are also discernible in the transverse momenta of the partons and in the lepton pair spectra, where the flow causes a violation of the so-called $M_T$ scaling.

The dependence of the equilibration of the parton plasma on the value of the strong coupling is studied in Au+Au collisions at LHC and at RHIC energies. With increasing coupling, the following are found to happen: (1) both thermal and chemical equilibration speed up, (2) in the final degree of equilibration, only quarks and antiquarks show obvious improvements but not gluons, and (3) the plasma cools much more rapidly. The deconfinement phase transition will therefore take place sooner and it naturally results in the shortening of the parton phase of the plasma. The exact duration of this phase is, however, sensitive to the value of the coupling. A change from ${\alpha }_s=0.3\mathrm{}$ to ${\alpha }_s=0.5\mathrm{}$, for example, reduces the lifetime of the parton phase at LHC by as much as 4.0 fm/$c$. The total generated entropy is another sensitive quantity to the coupling. Larger values of ${\alpha }_s$ will lead to entropy reduction and therefore reduction both in the duration of the mixed phase, assuming there is a first-order deconfinement phase transition, as well as in the final pion multiplicity. It is shown that the common choice of ${\alpha }_s=0.3\mathrm{}$ is not a good value for the entire duration of the evolution given that the system undergoes substantial changes from the beginning to the time that the deconfinement phase transition is about to take place assumed to be at $T_c\sim 200$ MeV. Instead, by using a more consistent simple recipe, the system is allowed to decide its own strength of the interactions which evolves with the system as it should. With this approach, ${\alpha }_s$ increases with time and this leads to acceleration in the equilibration even as equilibrium is near. This is opposite to the behavior of the equilibration of a molecular gas or ordinary many-body system where the interaction strength is fixed. In such a system, the net interactions will slow down as the system is near equilibrium.

The classical Yang-Mills equations are solved perturbatively in covariant gauge for a collision of two ultrarelativistic nuclei. The nuclei are taken as ensembles of classical color charges on eikonal trajectories. The classical gluon field is computed in coordinate space up to cubic order in the coupling constant $g$. We construct the Feynman diagrams corresponding to this field and show the equivalence of the classical and diagrammatic approaches. An argument is given which demonstrates that at higher orders in $g$ the classical description of the process breaks down. As an application, we calculate the energy, number, and multiplicity distributions of produced soft gluons and reproduce earlier results by Gunion and Bertsch and by Kovner, McLerran, and Weigert.

To predict two-boson correlation functions for emission from high-energy collisions using event simulators, the usual practice is to invoke the smoothness assumption. This assumption is questionable for cases with strong space-time correlations in the emission function. The validity of the assumption is explored here.

A unified approach to the pseudoscalar meson $(\pi$, $\eta$, and $K)$ photoproductions off nucleons are presented. It begins with the low energy QCD Lagrangian, and the resonances in the $s$ and $u$ channels are treated in the framework of the quark model. The duality hypothesis is imposed to limit the number of the $t$-channel exchanges. The CGLN amplitudes for each reaction are evaluated, which include both proton and neutron targets. The important role of the $S$-wave resonances in the second resonance region is discussed, and is particularly important for the $K$, $\eta$, and ${\eta }^{\prime }$ photoproductions.

Partial-wave amplitudes have been extracted from accurate data on $\overline{p}p\to {\pi }^{-}{\pi }^{+}$, combined with earlier data on $\overline{p}p\to {\pi }^0{\pi }^0$, by a method which incorporates the theoretical constraints of analyticity and crossing symmetry. The resulting solution gives a good fit to the annihilation data and is also consistent with the wealth of information in the crossed channel $\pi N\to \pi N$. The partial-wave amplitudes show evidence for resonances in all partial waves with $J<~5$, at least one of which, a ${J=0\mathrm{}}^{+}$ state (and possibly another with ${J=1\mathrm{}}^{-})$, is unlikely to have a simple $q\overline{q}$ structure.

The cross section of hard semiexclusive ${A(e,e}^{\prime }N\left)\right(A-1)$ reactions for fixed missing energy and momentum is calculated within the eikonal approximation. Relativistic dynamics and kinematics of high energy processes are unambiguously accounted for by using the analysis of appropriate Feynman diagrams. A significant dependence of the final state interactions on the missing energy is found, which is important for interpretation of forthcoming color transparency experiments. A new, more stringent kinematic restriction on the region where the contribution of short-range nucleon correlations is enhanced in semiexclusive knock-out processes is derived. It is also demonstrated that the use of light-cone variables leads to a considerable simplification of the description of high energy knock-out reactions.

We have measured the ${}^{26}\mathrm{Al}(n,{\alpha }_0{)}^{23}\mathrm{Mg}$ and ${}^{26}\mathrm{Al}{(n,p}_1{)}^{26}{\mathrm{Mg}}^{*}$ cross sections from thermal energy to approximately 10 keV and 70 keV, respectively. These reactions are thought to be the major mechanisms for the destruction of ${}^{26}\mathrm{Al}$ in many nucleosynthesis environments; hence, an accurate determination of their rates is important for understanding the observations of $\gamma$ rays from “live” ${}^{26}$Al in our galaxy and of “extinct” ${}^{26}$Al in meteorites. The astrophysical rate for the ${}^{26}\mathrm{Al}(n,{\alpha }_0{)}^{23}$Mg reaction determined from our measurements is in good agreement with the rate determined via inverse measurements. On the other hand, the rate we determined for the ${}^{26}\mathrm{Al}{(n,p}_1{)}^{26}{\mathrm{Mg}}^{*}$ reaction is significantly larger than previously reported. In addition, we were able to determine this rate in the temperature range below 0.2 GK which was not covered by previous measurements. This lower temperature range may be important for understanding the production of ${}^{26}$Al in Red Giant stars. Both of our rates are significantly different than the rates used in most nucleosynthesis calculations. We discuss the impact of our measurements on the nucleosynthesis of ${}^{26}$Al.

We examine the possibility that big-bang nucleosynthesis (BBN) may produce nontrivial amounts of ${}^6\mathrm{Li}$. If a primordial component of this isotope could be observed, it would provide a new fundamental test of big-bang cosmology, as well as new constraints on the baryon density of the universe. At present, however, theoretical predictions of the primordial ${}^6\mathrm{Li}$ abundance are extremely uncertain due to difficulties in both theoretical estimates and experimental determinations of the ${}^2\mathrm{H}(\alpha ,\gamma {)}^6\mathrm{Li}$ radiative capture reaction cross section. We also argue that present observational capabilities do not yet allow the detection of primeval ${}^6$Li in very metal-poor stars of the galactic halo. However, if the critical cross section is very high in its plausible range and the baryon density is relatively low, then improvements in ${}^6\mathrm{Li}$ detection capabilities may allow the establishment of ${}^6\mathrm{Li}$ as another product of BBN. It is also noted that a primordial ${}^6\mathrm{Li}$ detection could help resolve current concerns about the extragalactic D/H determination.

The nuclide ${}^{87}$Mo with $A=4n+3\mathrm{}$ and $T_z$=3/2 was reinvestigated via its $\beta$-delayed proton decay with $p-\gamma$ coincidence. The proton branching ratios in the decay of ${}^{87}$Mo populating the first 2${}^{+}$, 4${}^{+}$, and 6${}^{+}$ excited states in ${}^{86}$Zr have been measured to be (11$\pm$6)%, (2$\pm$1)%, and (2$\pm$1)%, respectively, which revise the previous results.

The neutron capture cross section of ${}^{48}$Ca was measured relative to the known gold cross section at $\mathrm{kT}$=52 keV using the fast cyclic activation technique. The experiment was performed at the Van de Graaff accelerator, Universität Tübingen. The new experimental result is in good agreement with a calculation using the direct capture model. The $1/v$ behavior of the capture cross section at thermonuclear energies is confirmed, and the adopted reaction rate which is based on several previous experimental investigations remains unchanged.