The ${}^{31}\mathrm{Si}$ nucleus was produced through the ${}^{18}\mathrm{O}({}^{18}\mathrm{O}, \alpha n$) fusion-evaporation reaction at $E_{\mathrm{lab}}=24\mathrm{MeV}$. Evaporated $\alpha$ particles from the reaction were detected and identified in the Microball detector array for channel selection. Multiple $\gamma$-ray coincidence events were detected in Gammasphere. The energy and angle information for the $\alpha$ particles was used to determine the ${}^{31}\mathrm{Si}$ recoil kinematics on an event-by-event basis for a more accurate Doppler correction. A total of 22 new states and 52 new $\gamma$ transitions were observed, including 14 from states above the neutron separation energy. The positive-parity states predicted by the shell-model calculations in the $sd$ model space agree well with experiment. The negative-parity states were compared with shell-model calculations in the $psdpf$ model space with some variations in the $N=20$ shell gap. The best agreement was found with a shell gap intermediate between that originally used for $A\approx 20$ nuclei and that previously adapted for ${}^{32,34}\mathrm{P}$. This variation suggests the need for a more universal cross-shell interaction.

Four light-mass nuclei are considered by an effective two-body clusterization method: ${}^7\mathrm{Li}$ as ${}^3\mathrm{H}+{}^4\mathrm{He},{}^7\mathrm{Be}$ as ${}^3\mathrm{He}+{}^4\mathrm{He},{}^8\mathrm{Be}$ as ${}^4\mathrm{He}+{}^4\mathrm{He}$, and ${}^6\mathrm{Li}$ as ${}^2\mathrm{H}+{}^4\mathrm{He}$. The low-energy spectra of the first three are determined from single-channel Lippmann-Schwinger equations. For the last, two uncoupled sets of equations are considered: those involving the $\underset{1}{{}^3\mathrm{S}}$ and those of the posited ${}^1{S}_0$ states of ${}^2\mathrm{H}$. Low-energy elastic scattering cross sections are calculated from the same ${}^2\mathrm{H}+{}^4\mathrm{He}$ Hamiltonian, for many angles and energies for which data are available. While some of these systems may be more fully described by many-body theories, this work establishes that a large amount of data may be explained by these two-body clusterizations.

Background: Fission has been found to be a dominating mode of deexcitation in heavy-ion induced reactions at high excitation energies. The phenomenon of heavy-ion induced fission has been extensively investigated with highly fissile actinide nuclei, yet there is a dearth of comprehensive understanding of underlying dynamics, particularly in the below actinide region and at low excitation energies.

Purpose: Prime objective of this work is to study different aspects of heavy-ion induced fission ensuing from the evolution of composite system formed via complete and/or incomplete fusion in the ${}^{12}\mathrm{C}+{}^{169}\mathrm{Tm}$ system at low incident energies, i.e., $E_{\mathrm{lab}}\approx 6.4$, 6.9, and 7.4 $A$ MeV, as well as to understand charge and mass distributions of fission fragments.

Method: The recoil-catcher activation technique followed by offline $\gamma$ spectroscopy was used to measure production cross sections of fission-like events. The evaporation residues were identified by their characteristic $\gamma$ rays and vetted by the decay-curve analysis. Charge and mass distributions of fission-like events were studied to obtain dispersion parameters of fission fragments.

Results: In the present work, 26 fission-like events ($32\le Z\le 49$) were identified at different excitation energies. The mass distribution of fission fragments is found to be broad and symmetric, manifesting their production via compound nuclear processes. The dispersion parameters of fission fragments obtained from the analysis of mass and isotopic yield distributions are found to be in good accord with the reported values obtained for different fissioning systems. A self-consistent approach was employed to determine the isobaric yield distribution.

Conclusions: The present work suggests that fission is one of the competing modes of deexcitation of complete and/or incomplete fusion composites at low excitation energies, i.e., $E^{*}\approx 57$, 63, and 69 MeV, where evaporation of light nuclear particle(s) and/or $\gamma$ rays are assumed to be the sole contributors. A single peaked broad Gaussian mass dispersion curve has corroborated the absence of any noncompound nuclear fission at the studied energies.

Recent experiments at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) have demonstrated that there are excellent opportunities to produce light baryonic clusters of exotic matter (strange and antimatter) in ultrarelativistic ion collisions. Within the hybrid-transport ultrarelativistic quantum molecular dynamics (UrQMD) model, we show that the coalescence mechanism can naturally explain the production of these clusters in the ALICE experiment at LHC. As a consequence of this mechanism, we predict the rapidity domains where the yields of such clusters are much larger than the observed one at midrapidity. This new phenomenon can lead to unique methods for producing exotic nuclei.

We present results about photon-production in relativistic heavy-ion collisions. The main novelty of our study is the calculation of the contribution of the early-stage photons to the photon spectrum. The initial stage is modeled by an ensemble of classical gluon fields which decay to a quark-gluon plasma via the Schwinger mechanism, and the evolution of the system is studied by coupling classical field equations to relativistic kinetic theory; photon production is then computed by including the pertinent collision processes into the collision integral. We find that the contribution of the early-stage photons to the direct photon spectrum is substantial for $p_T\approx 2$ GeV and higher, the exact value depending on the collision energy; therefore, we identify this part of the photon spectrum as the sign of the early stage. Moreover, the amount of photons produced during the early stage is not negligible with respect to those produced by a thermalized quark-gluon plasma: We support the idea that there is no dark age in relativistic heavy-ion collisions.

We describe a calculation of the spectrum of flavor-$\text{SU}\left(3\right)$ octet and decuplet baryons, their parity partners, and the radial excitations of these systems, made using a symmetry-preserving treatment of a vector $\times$ vector contact interaction as the foundation for the relevant few-body equations. Dynamical chiral symmetry breaking generates nonpointlike diquarks within these baryons and hence, using the contact interaction, flavor-antitriplet scalar, pseudoscalar, vector, and flavor-sextet axial-vector quark-quark correlations can all play active roles. The model yields reasonable masses for all systems studied and Faddeev amplitudes for ground states and associated parity partners that sketch a realistic picture of their internal structure: ground-state, even-parity baryons are constituted, almost exclusively, from like-parity diquark correlations, but orbital angular momentum plays an important role in the rest-frame wave functions of odd-parity baryons, whose Faddeev amplitudes are dominated by odd-parity diquarks.

Excited states in ${}^{186}\mathrm{Re}$ with spins up to $J=12\hslash$ were investigated in two separate experiments using ${}^{186}\mathrm{W}(d,2n)$ reactions at beam energies of 12.5 and 14.5 MeV. Two- and threefold $\gamma$-ray coincidence data were collected using the CAESAR and CAGRA spectrometers, respectively, each composed of Compton-suppressed high-purity germanium detectors. Analysis of the data revealed rotational bands built on several two-quasiparticle intrinsic states, including a long-lived $K^{\pi }=\left(8^{+}\right)$ isomer. Configuration assignments were supported by an analysis of in-band properties, such as $\left|g_K-g_R\right|$ values. The excitation energies of the observed intrinsic states were compared with results from multi-quasiparticle blocking calculations, based on the Lipkin-Nogami pairing approach, that included contributions from the residual proton-neutron interactions.

The $\beta$ decay of ${}^{100}\mathrm{Tc}$ has been studied by using the total absorption $\gamma$-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. In this work the new Decay Total Absorption $\gamma$-ray Spectrometer in coincidence with a cylindrical plastic $\beta$ detector has been employed. The $\beta$ intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first-excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random-phase approximation framework are also reported. Comparison of these calculations with our measurement serves as a benchmark for calculations of the double $\beta$ decay of ${}^{100}\mathrm{Mo}$.

The beta decays of ${}^{86}\mathrm{Br}$ and ${}^{91}\mathrm{Rb}$ have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the Ion Guide Isotope Separator On-Line facility in Jyväskylä and further purified using the JYFLTRAP. ${}^{86}\mathrm{Br}$ and ${}^{91}\mathrm{Rb}$ are considered to be major contributors to the decay heat in reactors. In addition, ${}^{91}\mathrm{Rb}$ was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results show that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renormalized. The relative impact of the studied decays in the prediction of the decay heat and antineutrino spectrum from reactors has been evaluated.

Fission fragment angular distributions for three reactions, ${}^{19}\mathrm{F}+{}^{182}\mathrm{W},{}^{19}\mathrm{F}+{}^{187}\mathrm{Re}$, and ${}^{19}\mathrm{F}+{}^{193}\mathrm{Ir}$, are measured in the laboratory energy range of 82–120 MeV. Extracted fission cross sections of the present systems as well as those of three others from literature $({}^{19}\mathrm{F}+{}^{192}\mathrm{Os},{}^{19}\mathrm{F}+{}^{194}\mathrm{Pt}$, and ${}^{19}\mathrm{F}+{}^{197}\mathrm{Au})$ are compared with the predictions of a statistical model which takes into account the effects of shell, orientation degree of freedom, and collective enhancement in level density (CELD). In all the cases, the standard statistical model predictions overestimate the measured fission cross section, indicating the presence of some amount of dynamical effects in the exit channel. A dissipation strength of $2\times {10}^{21}{\mathrm{s}}^{-1}$ is found to be sufficient to reproduce the data of all the reactions. No scaling of fission barrier height to fit the data is required.

In a potential model, I have estimated decay widths for ${}^{11}\mathrm{O}$ to ${}^9\mathrm{C}+2p$ for sequential decay through ${}^{10}\mathrm{N}$ resonances and by simultaneous $2p$ (${}^2\mathrm{He}$) decay by integrating over the relevant energy profiles. Results indicate that sequential decays through positive-parity resonances are only slightly smaller than those through negative-parity resonances. Simultaneous decay is predicted to be larger than sequential.

Background: Several investigations on the complete-incomplete fusion (CF-ICF) dynamics of $\alpha$-cluster well-bound nuclei have been contemplated above the Coulomb barrier $(\sim 4$–7 MeV/nucleon) in recent years. It is therefore expected to observe significant ICF over CF in the reactions induced by a weakly bound $\alpha$-cluster nucleus at slightly above the barrier.

Purpose: Study of the CF-ICF dynamics by measuring the populated residues in the weakly bound ${}^7\mathrm{Li}+{}^{\text{nat}}\mathrm{Mo}$ system at energies slightly above the Coulomb barrier to well above it.

Method: In order to investigate CF-ICF in the loosely bound system, ${}^7\mathrm{Li}$ beam was bombarded on the ${}^{\text{nat}}\mathrm{Mo}$ foils, separated by the aluminium (Al) catcher foils alternatively, within $\sim 3$–6.5 MeV/nucleon. Evaporation residues produced in each foil were identified by the off-line $\gamma$-ray spectrometry. Measured cross section data of the residues were compared with the theoretical model calculations based on the equilibrium (EQ) and pre-equilibrium (PEQ) reaction mechanisms.

Results: The experimental cross section of ${}^{101\text{m},100,99\text{m},97}\mathrm{Rh},{}^{97,95}\mathrm{Ru},{}^{99\text{m},96,95,94,93\text{m}+\text{g}}\mathrm{Tc}$, and ${}^{\text{93m}}\mathrm{Mo}$ residues measured at various projectile energies were satisfactorily reproduced by the simplified coupled channel approach in comparison to single barrier penetration model calculation. Significant cross section enhancement in the $\alpha$-emitting channels was observed compared to EQ and PEQ model calculations throughout observed energy region. The ICF process over CF was analyzed by comparing with EMPIRE. The increment of the incomplete fusion fraction was observed with increasing projectile energies.

Conclusions: Theoretical model calculations reveal that the compound reaction mechanism is the major contributor to the production of residues in ${}^7\mathrm{Li}+{}^{\text{nat}}\mathrm{Mo}$ reaction. Theoretical evaluations substantiate the contribution of ICF over the CF in $\alpha$-emitting channels. EMPIRE estimations shed light on its predictive capability of cross sections of the residues from the heavy-ion induced reactions.

Vector-boson-tagged jet production in collisions of heavy nuclei opens new opportunities to study parton shower formation and propagation in strongly interacting matter. It has been argued to provide a golden channel that can constrain the energy loss of jets in the quark-gluon plasma created in heavy ion reactions. We present theoretical results for isolated-photon-tagged and $Z^0$-boson-tagged jet production in Pb + Pb collisions with $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ at the LHC. Specifically, we evaluate the transverse momentum imbalance ${\mathrm{x}}_{\mathrm{JV}}$ distribution and nuclear modification factor ${\mathrm{I}}_{\mathrm{AA}}$ of tagged jets and compare our theoretical calculations to recent experimental measurements by ATLAS and CMS collaborations. Our analysis, which includes both collisional and radiative energy losses, sheds light on their relative importance versus the strength of jet-medium interactions and helps quantify the amount of out-of-cone radiation of predominantly prompt quark-initiated jets.

We compare two approaches in modeling repulsive interactions among hadrons: the excluded volume approximation and the $S$-matrix formalism. These are applied to study the thermodynamics of the $\pi N\mathrm{\Delta }$ system. It is shown that the introduction of an extraneous repulsion between pions and nucleons via the excluded volume approach, in addition to the interaction that generates the $\mathrm{\Delta }$-resonance, is incompatible with the analysis based on the physical phase shift of pion-nucleon scattering in the $P_{33}$ channel. This finding suggests that the repulsive force between hadrons is interaction-channel dependent and is hence unlikely to be captured by a single phenomenological parameter. The $S$-matrix approach employed here can be used, however, to provide useful estimates of the magnitude of the effective eigenvolume.

The doubly magic ${}^{208}\mathrm{Pb}$ nucleus is a bottleneck at the termination of the $s$-process path due to its very low neutron capture cross section. This cross section is also important for the decomposition of $s$, $r$ processes and U/Th radiogenic decay contributions to the Pb-Bi solar abundances. The ${}^{208}\mathrm{Pb}(n,\gamma ){}^{209}\mathrm{Pb}$ cross section was measured at the Soreq Applied Research Accelerator Facility Phase I using an intense quasi-Maxwellian neutron source produced by irradiation of the liquid-lithium target with a 1.5-mA continuous-wave proton beam at 1.94 MeV. The cross section was measured by counting the $\beta$ activity from the irradiated lead target. The measurement allowed us to evaluate the Maxwellian averaged cross section (MACS) at 30 keV obtaining a value of 0.33(2) mb. This has been compared with the earlier activation and time-of-flight measurements found in the literature. The MACS cross-sectional value of the ${}^{63}\mathrm{Cu}(n,\gamma ){}^{64}\mathrm{Cu}$ reaction was determined in the same experiment and is compared to a recent published value.

Background: The energy weighted sum rules of the single-particle spectral functions provide a quantitative understanding of the fragmentation of nuclear states due to short-range and tensor correlations.

Purpose: The aim of this paper is to compare on a quantitative basis the single-particle spectral function generated by different nuclear Hamiltonians in symmetric nuclear matter using the first three energy-weighted moments.

Method: The spectral functions are calculated in the framework of the self-consistent Green's function approach at finite temperature within a ladder resummation scheme. We analyze the first three moments of the spectral function and connect these to the correlations induced by the interactions between the nucleons in symmetric nuclear matter. In particular, the variance of the spectral function is directly linked to the dispersive contribution of the self-energy. The discussion is centered around two- and three-body chiral nuclear interactions, with and without renormalization, but we also provide results obtained with the traditional phase-shift-equivalent CD-Bonn and Av18 potentials.

Results: The variance of the spectral function is particularly sensitive to the short-range structure of the force, with hard-core interactions providing large variances. Chiral forces yield variances which are an order of magnitude smaller and, when tamed using the similarity renormalization group, the variance reduces significantly and in proportion to the renormalization scale. The presence of three-body forces does not substantially affect the results.

Conclusions: The first three moments of the spectral function are useful tools in analyzing the importance of correlations in nuclear ground states. In particular, the second-order moment provides a direct insight into dispersive contributions to the self-energy and its value is indicative of the fragmentation of single-particle states.

High-spin states in the ${}^{188}\mathrm{Pt}$ nucleus have been investigated employing the ${}^{174}\mathrm{Yb}({}^{18}\mathrm{O},4n){}^{188}\mathrm{Pt}$ reaction. The level scheme has been significantly extended with the addition of several new $\gamma$ rays. The Indian National Gamma Array (INGA) spectrometer consisting of eighteen clover Ge detectors facilitated angular correlation and linear polarization measurements for spin-parity assignment of levels. The $I^{\pi }=5^{-}$ semi-decoupled band has been investigated in detail, and the long-standing ambiguity regarding the correct ordering of associated $\gamma$ rays is now removed with the new observation of transitions linking the even-spin levels to the odd-spin ones. A weak, $\mathrm{\Delta }I=2$ sequence of $\gamma$ rays with alignment and moment of inertia similar to the yrast, even-spin, rotation-aligned neutron $i_{13/2}$ band has been newly observed. Cranking calculations suggest that this new odd-spin sequence arises from the excitation of a valence quasineutron to the next $i_{13/2}$ level.

Starting from the relativistic form of the Bonn potential as a bare nucleon-nucleon interaction, the full relativistic Brueckner-Hartree-Fock (RBHF) equations are solved for finite nuclei in a fully self-consistent basis. This provides a relativistic ab initio calculation of the ground state properties of finite nuclei without any free parameters and without three-body forces. The convergence properties for the solutions of these coupled equations are discussed in detail for the example of the nucleus ${}^{16}\mathrm{O}$. The binding energies, radii, and spin-orbit splittings of the doubly magic nuclei ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$ are calculated and compared with the earlier RBHF calculated results in a fixed Dirac Woods-Saxon basis and other nonrelativistic ab initio calculated results based on pure two-body forces.

Background: At the forefront of the nuclear science, production of new neutron-rich isotopes is continuously pursued at accelerator laboratories all over the world. To explore the currently unknown territories in the nuclear chart far away from the stability, reliable theoretical predictions are inevitable.

Purpose: To provide a reliable prediction of production cross sections taking into account secondary deexcitation processes, both particle evaporation and fission, a new method called TDHF+GEMINI is proposed, which combines the microscopic time-dependent Hartree-Fock (TDHF) theory with a sophisticated statistical compound-nucleus deexcitation model, GEMINI++.

Methods: Low-energy heavy ion reactions are described based on three-dimensional Skyrme-TDHF calculations. Using the particle-number projection method, production probabilities, total angular momenta, and excitation energies of primary reaction products are extracted from the TDHF wave function after collision. Production cross sections for secondary reaction products are evaluated employing GEMINI++. Results are compared with available experimental data and widely used grazing calculations.

Results: The method is applied to describe cross sections for multinucleon transfer processes in ${}^{40}\mathrm{Ca}+{}^{124}\mathrm{Sn}$ ($E_{\mathrm{c}.\mathrm{m}.}\simeq 128.54\mathrm{MeV}$), ${}^{48}\mathrm{Ca}+{}^{124}\mathrm{Sn}$ ($E_{\mathrm{c}.\mathrm{m}.}\simeq 125.44\mathrm{MeV}$), ${}^{40}\mathrm{Ca}+{}^{208}\mathrm{Pb}$ ($E_{\mathrm{c}.\mathrm{m}.}\simeq 208.84\mathrm{MeV}$), ${}^{58}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ ($E_{\mathrm{c}.\mathrm{m}.}\simeq 256.79\mathrm{MeV}$), ${}^{64}\mathrm{Ni}+{}^{238}\mathrm{U}$ ($E_{\mathrm{c}.\mathrm{m}.}\simeq 307.35\mathrm{MeV}$), and ${}^{136}\mathrm{Xe}+{}^{198}\mathrm{Pt}$ ($E_{\mathrm{c}.\mathrm{m}.}\simeq 644.98\mathrm{MeV}$) reactions at energies close to the Coulomb barrier. It is shown that the inclusion of secondary deexcitation processes, which are dominated by neutron evaporation in the present systems, substantially improves agreement with the experimental data. The magnitude of the evaporation effects is very similar to the one observed in grazing calculations. TDHF+GEMINI provides better description of the absolute value of the cross sections for channels involving transfer of more than one proton, compared to the grazing results. However, there remain discrepancies between the measurements and the calculated cross sections, indicating a limit of the theoretical framework that works with a single mean-field potential. Possible causes of the discrepancies are discussed.

Conclusions: To perfectly reproduce experimental cross sections for multinucleon transfer processes, one should go beyond the standard self-consistent mean-field description. Nevertheless, the proposed method will provide valuable information to optimize production mechanisms of new neutron-rich nuclei through its microscopic, nonempirical predictions.