Low- and medium-spin states have been investigated in the even-even nucleus ${}^{84}\mathrm{Zr}$ by using in-beam γ-ray spectroscopy via the reactions ${}^{59}\mathrm{Co}{(}^{28}\mathrm{Si},p2n)$ and ${}^{58}\mathrm{Ni}{(}^{32}\mathrm{S},\alpha 2p)$ at beam energies of 99 and 135 MeV, respectively. Several new levels have been identified, including a new even-spin sequence of the γ-vibrational band. The previously known sequence has been found to be built on a $3^{+}$ state at 1575.3 keV representing the odd-spin sequence. In addition, the ${\beta }^{+}/\mathrm{EC}$ decay of mass-separated ${}^{84}\mathrm{Nb}$ sources has been studied by β- and γ-ray spectroscopy following the bombardment of a thin ${}^{58}\mathrm{Ni}$ target with ${}^{28}\mathrm{Si}$ ions at 94 MeV. Some low-lying daughter states up to spin and parity of $4^{+}$ have been identified in ${}^{84}\mathrm{Zr},$ and a half-life of $9.5\pm 1.0\mathrm{s}$ has been measured for the ${}^{84}\mathrm{Nb}$ ground-state decay. The systematics of γ-vibrational states in even-even Zr nuclei and a comparison with model predictions indicate increasing $\gamma$ softness and triaxiality as the spherical neutron shell closure at $N=50\mathrm{}$ is approached. Using an empirical estimate, a triaxiality of about $25°$ has been extracted for ${}^{84}\mathrm{Zr}.$ Furthermore, a negative-parity structure of $4^{-}$ and $6^{-}$ states which is similar to other $N=44\mathrm{}$ isotones has been identified in ${}^{84}\mathrm{Zr}$ as a two-quasineutron excitation.

We measured, for the first time, the mass distribution of ${}^{240}\mathrm{Pu}$ fission fragments following the β-vibrational resonance, whose level is formed on the second minimum of the double-humped fission barrier. The distribution shows an asymmetric mass distribution similar to the one observed for thermal neutron-induced fission of ${}^{239}\mathrm{Pu}$ and isomeric fission of ${}^{240}\mathrm{Pu}.$ This indicates that the ${}^{240}\mathrm{Pu}$ system following the β-vibrational resonance descends into a fission valley which is identical to the fission valley of the ${}^{240}\mathrm{Pu}$ isomer and ${}^{239}\mathrm{Pu}{(n}_{\mathrm{th}},f).\mathrm{}$

We calculate p, ${\pi }^{\pm },$ $K^{\pm },$ and $\Lambda (+{\Sigma }^0)$ rapidity distributions and compare to experimental data from SIS to SPS energies within the Ultrarelativistic-Quantum-Molecular Dynamics and Hadron-String Dynamics transport approaches that are both based on string, quark, diquark $(q,$ $\overline{q},$ $qq,$ $\overline{q}\overline{q}),$ and hadronic degrees of freedom. The two transport models do not include any explicit phase transition to a quark-gluon plasma. It is found that both approaches agree rather well with each other and with the experimental rapidity distributions for protons, Λ’s, ${\pi }^{\pm },$ and $K^{\pm }.$ In spite of this apparent agreement both transport models fail to reproduce the maximum in the excitation function for the ratio $K^{+}/{\pi }^{+}$ found experimentally between 11 and 40 A GeV. A comparison to the various experimental data shows that this “failure” is dominantly due to an insufficient description of pion rapidity distributions rather than missing “strangeness.” The modest differences in the transport model results—on the other hand—can be attributed to different implementations of string formation and fragmentation that are not sufficiently controlled by experimental data for the “elementary” reactions in vacuum.

The chiral invariant quantum hadrodynamics (QHD) III model of Serot and Walecka is applied in the calculation of some meson properties. The electromagnetic interaction is included by extending the symmetry of the model to the local $\mathrm{U}\mathrm{}\left(1\right)\mathrm{}\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L$ group. The minimal and nonminimal contributions to the electromagnetic Lagrangian are obtained in a new representation of QHD-III. Strong decays of the axial-vector meson, $a_1\to \pi \rho ,a_1\to \pi \sigma ,$ and the electromagnetic decays $\overrightarrow{\rho }\pi \pi \gamma ,a_1\to \pi \gamma ,$ and $\overrightarrow{\rho }\pi \gamma$ are calculated. The low-energy parameters for the $\pi -\pi$ scattering are calculated in the tree-level approximation. The effect of the auxiliary Higgs bosons, introduced in QHD-III in order to generate masses of the vector and axial-vector mesons via the Higgs mechanism, is studied as well. This is done on the tree level for $\pi -\pi$ scattering and on the level of one-loop diagrams for the $a_1\to \pi \gamma$ decay. It is demonstrated that the model successfully describes some features of meson phenomenology in the nonstrange sector.

An attempt was made to measure the excitation function of the cross section for the ${}^8\mathrm{Li}(n,\gamma {)}^9\mathrm{Li}$ reaction by performing the inverse reaction ${}^9\mathrm{Li}(\gamma {,n)}^8\mathrm{Li},$ with the equivalent photons in the electric field of nuclei in a Pb target providing the $\gamma$ rays for the reaction. The energy spectrum of lithium nuclei in coincidence with neutrons had no discernible peak where any beam-velocity ${}^8\mathrm{Li}’\mathrm{s}$ would be located. Statistically, a Gaussian-shaped ${}^8\mathrm{Li}$ peak could have been present with $30\pm 29$ counts, which we interpreted as consistent with zero, with a two-standard-deviation upper limit of 87 counts. Using the fact that neutron capture on ${}^8\mathrm{Li}$ must be dominantly s-wave capture, and applying detailed balance, we obtained, with E in eV, ${\sigma }_{n,\gamma }<{930E}^{-1/2}\mu \mathrm{b}.$ The corresponding limit on the astrophysical reaction rate is $<790\mathrm{}$ ${\mathrm{cm}}^3{\mathrm{mol}}^{-1}{\mathrm{s}}^{-1}.$ Theoretical predictions of the reaction rate have exceeded our upper limit by factors of 3–50.

Breakup in nucleon-deuteron scattering is described. The description is based on a coupled-channel two-baryon potential that allows for the virtual excitation of a nucleon to a $\Delta$ isobar. The Coulomb interaction is not included. Channel coupling gives rise to an effective three-nucleon force. The three-particle scattering equations are solved by real-axis integration using a separable expansion of the two-baryon transition matrix. Examples for spin-averaged and spin-dependent observables are calculated and compared with experimental data.

The second excited state ${(J}^{\pi }{=1/2\mathrm{}}^{+},$ $\mathcal{l}=0)$ of the proton-rich nucleus ${}^{19}\mathrm{Na}$ has been observed for the first time using the elastic scattering reaction ${}^1\mathrm{H}{(}^{18}\mathrm{Ne}{,}^1\mathrm{H}{)}^{18}\mathrm{Ne}.$ An intense $(4\mathrm{}\times {10}^6\mathrm{pps})$ ${}^{18}\mathrm{Ne}$ radioactive beam was produced at the CRC-RIB facility at Louvain-la-Neuve to bombard a polyethylene target. The recoil protons were detected at 20 different angles in the LEDA segmented silicon detector. The resulting elastic scattering cross sections have been analyzed using a global R-matrix fit. We find that the second excited state in ${}^{19}\mathrm{Na}$ lies at the center-of-mass energy $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=1.066\mathrm{}\pm 0.003\mathrm{MeV}$ with respect to the ${}^{18}\mathrm{Ne}+p$ threshold, and has a proton width ${\Gamma }_{\mathrm{p}}=101\mathrm{}\pm 3\mathrm{}\mathrm{keV}.$ The Coulomb shift between the ${1/2}^{+}$ mirror levels in ${}^{19}\mathrm{O}$ and ${}^{19}\mathrm{Na}$ is 0.73 MeV, among the largest values currently observed in light exotic nuclei.

A highly specialized two-center shell model has been developed accounting for the splitting of a deformed parent nucleus into two ellipsoidaly deformed fragments. The potential is based on deformed oscillator wells in direct correspondance with the shape change of the nuclear system. For the first time a potential responsible for the necking part between the fragments is introduced on a potential theory basis. As a direct consequence, spin-orbit ls and ${\mathbf{l}}^2$ operators are calculated as shape dependent. The level scheme evolution along the fission path for pairs of ellipsoidaly deformed fragments is calculated. The Strutinsky method yields the shell corrections for different mass asymmetries from the superheavy nucleus ${}^{306}122$ and ${}^{252}\mathrm{Cf}$ all along the splitting process.

The indication for the $\alpha$ decay of ${}^{180}\mathrm{W}$ with a half-life $T_{1/2}^{\alpha }{=1.1\mathrm{}}_{-0.4}^{+0.8\mathrm{}}\left(\mathrm{stat}\right)\pm 0.3\left(\mathrm{syst}\right)\times {10}^{18}$ yr has been observed for the first time with the help of the superlow background ${}^{116}{\mathrm{CdWO}}_4$ crystal scintillators. In a conservative approach the lower limit on half-life of ${}^{180}\mathrm{W}$ has been established as $T_{1/2}^{\alpha }{(}^{180}\mathrm{W})>~0.7\times {10}^{18}$ yr at 90% C.L. In addition, new $T_{1/2}^{\alpha }$ bounds were set for $\alpha$ decay of ${}^{182}\mathrm{W},{}^{183}\mathrm{W},{}^{184}\mathrm{W},$ and ${}^{186}\mathrm{W}$ at the level of ${10}^{20}$ yr.

$\beta$ decay of ${}^{56,57,58}\mathrm{V}$ has been used to populate low-energy levels of ${}^{56,57,58}\mathrm{Cr},$ respectively. The low-energy levels of the even-even Cr isotopes and $\beta$-decay half-lives and branching ratios of the parent V isotopes are compared to results of shell-model calculations. The Cr energy level calculations were completed in the full $\mathrm{pf}$-model space, using several different interactions. The systematic variation of ${E(2\mathrm{}}_1^{+}),$ which is indicative of a subshell closure at $N=32,$ was best reproduced in calculations using a pf-shell-model interaction based on effective two-body matrix elements with some replacement by the G matrix.

Collective structures in ${}^{172}\mathrm{Pt}$ have been investigated by measuring in-beam $\gamma$ rays with mass selection and the recoil-decay tagging technique. The discrepancy in the ground-state band from previous studies has been resolved, and a new collective structure that is likely based on an octupole vibration has been identified. A band mixing model is used to determine the properties of the competing near-spherical and deformed ground-state sequences in the light Os-Pt-Hg-Pb region. Evidence for a reduction of deformation in the deformed vacuum structure below $N=98\mathrm{}$ is presented.

The properties of the states of the alternating parity bands in actinides and Ba, Ce, and Nd isotopes are analyzed within a cluster model. The model is based on the assumption that cluster-type shapes are produced by the collective motion of the nuclear system in the mass asymmetry coordinate. The calculated spin dependences of the parity splitting and of the electric multipole transition moments are in agreement with the experimental data.

Shannon’s information entropies in position and momentum space and their sum S are calculated for various $s-p$ and $s-d$ shell nuclei using a correlated one-body density matrix depending on the harmonic oscillator size $b_0$ and the short range correlation parameter y which originates from a Jastrow correlation function. It is found that the information entropy sum for a nucleus depends only on the correlation parameter y through the simple relation ${S=s}_{0A}{+s}_{1A}{y}^{-{\lambda }_{\mathrm{sA}}},$ where $s_{0A},$ $s_{1A},$ and ${\lambda }_{\mathrm{sA}}$ depend on the mass number A. A similar approximate expression is also valid for the root-mean-square radius of the nucleus as function of y leading to an approximate expression which connects S with the root-mean-square radius. Finally, we propose a method to determine the correlation parameter from the above property of S as well as the linear dependence of S on the logarithm of the number of nucleons.

We study Drell-Yan (DY) dilepton production in proton(deuterium)-nucleus and in nucleus-nucleus collisions within the light-cone color-dipole formalism. This approach is especially suitable for predicting nuclear effects in the DY cross section for heavy-ion collisions, as it provides the impact parameter dependence of nuclear shadowing and transverse momentum broadening, quantities that are not available from the standard parton model. For $p\left(D\right)+A$ collisions we calculate nuclear shadowing and investigate nuclear modification of the DY transverse momentum distribution at the Relativistic Heavy Ion Collider and the Large Hadron Collider for kinematics corresponding to coherence length much longer than the nuclear size. Calculations are performed separately for transversely and longitudinally polarized DY photons, and predictions are presented for the dilepton angular distribution. Furthermore, we calculate nuclear broadening of the mean transverse momentum squared of DY dileptons as function of the nuclear mass number and energy. We also predict nuclear effects for the cross section of the DY process in heavy-ion collisions. We found a substantial nuclear shadowing for valence quarks, stronger than for the sea.

We investigate the spectral function of light quarks in infinite quark matter using a simple, albeit self-consistent model. The interactions between the quarks are described by the SU(2) Nambu–Jona-Lasinio model. Currently mean-field effects are neglected and all calculations are performed in the chirally restored phase at zero temperature. Relations between correlation functions and collision rates are used to calculate the spectral function in an iterative process.

The evolution of very low-metallicity, massive stars depends critically on the amount of CNO nuclei that they produce. Alternative paths from the slow $3\alpha$ process to produce CNO seed nuclei could change their fate. The ${}^{11}\mathrm{C}(p,\gamma {)}^{12}\mathrm{N}$ reaction is an important branch point in one such alternative path. At energies appropriate to stellar evolution of very low-metallicity, massive stars, nonresonant capture dominates the reaction rate. We have determined the astrophysical S factor for $\mathrm{the}{\hspace{0.5em}}^{11}\mathrm{C}(p,\gamma {)}^{12}\mathrm{N}$ reaction using the asymptotic normalization coefficient for ${}^{12}{\overrightarrow{\mathrm{N}}}^{11}\mathrm{C}+p$ to fix the nonresonant capture rate. In our experiment, a 110 MeV ${}^{11}\mathrm{C}$ radioactive beam was used to study ${\mathrm{the}}^{14}\mathrm{N}{(}^{11}\mathrm{C}{,}^{12}\mathrm{N}{)}^{13}\mathrm{C}$ peripheral transfer reaction and the asymptotic normalization coefficient, ${(C}_{p_{\mathrm{eff}}}^{{}^{12}N}{)}^2{=(C}_{p_{1/2}}^{{}^{12}N}{)}^2{+(C}_{p_{3/2}}^{{}^{12}N}{)}^2=1.73\mathrm{}\pm 0.25{\mathrm{fm}}^{-1},$ was extracted from the measured cross section. The contributions from the second resonance and interference effects were estimated using an R-matrix approach with the measured asymptotic normalization coefficient and the latest value for ${\Gamma }_{\gamma }.$ We find the S factor for ${}^{11}\mathrm{C}(p,\gamma {)}^{12}\mathrm{N}$ is significantly larger than previous estimates. As a result, the required density for it to contribute is reduced, and more CNO material may be produced.

Regular sequences of narrow peaks have been observed in the missing mass spectra in the reactions $p\overrightarrow{p}p{\pi }^{+}X$ and $p\overrightarrow{d}{\mathrm{ppX}}_1$ below the pion-production threshold. They are interpreted in the literature as manifestations of supernarrow light dibaryons, nucleon resonances, or light pions forming resonance states with the nucleon in its ground state. We discuss how the existence of such exotic states would affect the properties of nuclear systems. We show that the neutron star structure is drastically changed in all three cases. We find that in the presence of dibaryons or nucleon resonances the maximal possible mass of a neutron star would be smaller than the observational limit. The presence of light pions does not contradict the observed neutron star masses. Light pions allow for the existence of extended nuclear objects of arbitrary size, bound by strong and electromagnetic forces.

A one-boson exchange (OBE) potential model, based on the Nijmegen model D potential, for the ${}^1{S}_0,$ $S=-2$ interaction is analyzed with emphasis on the role of coupling between the ΛΛ, $N\Xi ,$ and ΣΣ channels. Singlet scalar exchange, an approximation to two-pion exchange, is significant in all channels; surprisingly, the one-pion exchange component is almost negligible. The size of the channel coupling as a function of the overall strength of the OBE model potential is examined. Implications of the analysis for the binding energy of ${}_{\Lambda \Lambda }^6\mathrm{He}$ are considered; the new experimental datum may suggest a consistency between the extracted ΛΛ matrix element and the relation implied by SU(3) among OBE baryon-baryon interactions.

The astrophysical factor $S_{17}$ for ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction is reliably extracted from the transfer reaction ${}^7\mathrm{Be}{\mathrm{}(d,n)\mathrm{}}^8\mathrm{B}$ at $E=7.5\mathrm{}$ MeV with the asymptotic normalization coefficient method. The transfer reaction is accurately analyzed with CDCC based on a three-body model. This analysis is free from uncertainties of the optical potentials having been crucial in the previous DWBA analyses.

The ${}^{15}\mathrm{O}(\alpha ,\gamma {)}^{19}\mathrm{Ne}$ reaction is one of two routes for breakout from the hot CNO cycles into the $\mathrm{rp}$ process in accreting neutron stars. Its astrophysical rate depends critically on the decay properties of excited states in ${}^{19}\mathrm{Ne}$ lying just above the ${}^{15}\mathrm{O}+\alpha$ threshold. We have measured the $\alpha$-decay branching ratios for these states using the ${p(}^{21}\mathrm{Ne}{,t)}^{19}\mathrm{Ne}$ reaction at 43 MeV/nucleon. Combining our measurements with previous determinations of the radiative widths of these states, we conclude that no significant breakout from the hot CNO cycle into the $\mathrm{rp}$ process in novas is possible via ${}^{15}\mathrm{O}(\alpha ,\gamma {)}^{19}\mathrm{Ne},$ assuming that current models accurately represent their temperature and density conditions.