We introduce the modular algorithm for relativistic treatment of heavy ion interactions (MARTINI), a comprehensive event generator for the hard and penetrating probes in high-energy nucleus-nucleus collisions. Its main components are a time-evolution model for the soft background, PYTHIA 8.1, and the McGill-Arnold, Moore, and Yaffe (AMY) parton-evolution scheme, including radiative as well as elastic processes. This allows us to generate full event configurations in the high $p_T$ region that take into account thermal quantum chromodynamic (QCD) and quantum electrodynamic (QED) effects as well as effects of the evolving medium. We present results for the neutral pion nuclear modification factor in $\mathrm{Au}+\mathrm{Au}$ collisions at the BNL Relativistic Heavy Ion Collider as a function of $p_T$ for different centralities and also as a function of the angle with respect to the reaction plane for noncentral collisions. Furthermore, we study the production of high-transverse-momentum photons, incorporating a complete set of photon-production channels.

We explore intensity correlations for thermal photons having $K_T⩽2\hspace{0.5em}\mathrm{GeV}/c$ for central collisions of heavy nuclei at Relativistic Heavy Ion Collider and Large Hadron Collider energies. These photons get competing contributions from the quark and hadronic phases. This competition gives rise to a unique structure, especially in the outward correlation function, owing to the interference between the photons from the two sources. The temporal separation of the two sources provides the lifetime of the system and their strengths provide the relative contribution of the two phases. The results are found to be quite sensitive to the quark-hadron phase transition temperature and the formation time of the plasma.

A Monte Carlo event generator has been developed assuming thermal production of hadrons. The system under consideration is sampled grand canonically in the Boltzmann approximation. A reweighting scheme is then introduced to account for conservation of charges (baryon number, strangeness, electric charge) and energy and momentum, effectively allowing for extrapolation of grand canonical results to the microcanonical limit. This method has two strong advantages compared to analytical approaches and standard microcanonical Monte Carlo techniques in that it is capable of handling resonance decays as well as (very) large system sizes.

The Fokker-Planck (FP) equation has been solved to study the interaction of nonequilibrated heavy quarks with the quark gluon plasma expected to be formed in heavy ion collisions at Relativistic Heavy Ion Collider energies. Solutions of the FP equation have been convoluted with the relevant fragmentation functions to obtain the $D$ and $B$ meson spectra. Results are compared with experimental data measured by the STAR Collaboration. It is found that the present experimental data cannot distinguish $p_T$ spectra obtained from the equilibrium versus the nonequilibrium charm distributions. Data at lower $p_T$ may play a crucial role in making the distinction between the two. The nuclear suppression factor $R_{\mathit{AA}}$ for nonphotonic single-electron spectra resulting from semileptonic decays of hadrons containing heavy flavors has been evaluated using the present formalism. It is observed that the experimental data on the nuclear suppression factor of nonphotonic electrons can be reproduced within this formalism by enhancing the perturbative QCD cross sections by a factor of 2, provided that the expansion of the bulk matter is governed by the velocity of sound $c_s~1/\sqrt{4}$. The ideal-gas equation of state fails to reproduce the data even with enhancement of the perturbative QCD cross sections by a factor of 2.

I show that quantum chromodynamics in four dimensions (QCD4) with transverse confinement can be approximately compactified into QCD2 with a transverse quark mass $m_T$ that is obtained by solving a set of coupled transverse eigenvalue equations. In the limits of a strong coupling and a large number of flavors, QCD2 further admits Schwinger QED2-type bosonized solutions. I therefore examine phenomenologically the space-time dynamics of particles produced in string fragmentation by studying the Wigner function of bosons produced in Schwinger QED2, which mimics many features of string fragmentation in quantum chromodynamics. I find that particles with momenta in different regions of the rapidity plateau are produced at the initial moment of string fragmentation as a quark pulls away from an antiquark at high energies, in contrast to classical depictions of string fragmentation with longitudinal space-momentum-time ordering.

The formation of a deeply bound $K^{-}\mathit{pp}$ state with $I=1/2$, $J^{\pi }=0^{-}$, by the ${}^3\mathrm{He}$(in-flight $K^{-}$,$n$) reaction is theoretically investigated in a distorted-wave impulse approximation using the Green’s function method. The expected inclusive and semiexclusive spectra at $p_{K^{-}}=1.0$ GeV/$c$ and ${\theta }_{\mathrm{lab}}=0^{°}$ are calculated for the forthcoming J-PARC E15 experiment. We demonstrate these spectra with several phenomenological $K^{-}$-“$\mathit{pp}$” optical potentials $U^{\mathrm{opt}}(E)$ that have an energy-dependent imaginary part multiplied by a phase space suppression factor, fitting to recent theoretical predictions or experimental candidates of the $K^{-}\mathit{pp}$ bound state. The results show that a cusplike peak at the $\pi \Sigma N$ threshold is a unique signal for the $K^{-}\mathit{pp}$ bound state in the spectrum including the $[K^{-}\mathit{pp}]\to Y+N$ decay process from two-nucleon $K^{-}$ absorption, as well as a distinct peak of the $K^{-}\mathit{pp}$ bound state. The shape of the spectrum is explained by the trajectory of a moving pole of the $K^{-}\mathit{pp}$ bound state in the complex energy plane. The importance of the $[K^{-}\mathit{pp}]\to Y+N$ spectrum to extract clear evidence of the $K^{-}\mathit{pp}$ bound state is emphasized.

In this work I continue the investigation of the space-time evolution of the hadronization process on the basis of the semi-inclusive deep inelastic scattering data on nuclei obtained by the HERMES experiment at the Deutsches Elektronen Synchrotron (DESY). Results of previous articles from our group, together with the analysis performed in this work, show that a ratio of multiplicities for the nucleus and deuterium (per nucleon), $R_M^h$, can be presented in the form of a function of a single variable $\tau$, which has the physical meaning of the formation time of the hadron. This $\tau$ scaling is a function of two variables: the energy of the virtual photon $\nu$ and the fraction of that energy, $z$, carried by the final hadron. Moreover, $R_M^h$ can be parametrized in the form of a linear polynomial $a_{11}+\tau a_{12}$, where the parameters $a_{11}$ and $a_{12}$ do not depend on $\nu$ and $z$.

Some predictions concerning possible results of the future experiments at the Thomas Jefferson National Accelerator Facility (JLab) on the pion form factor $F_{\pi }(Q^2)$ are made. The calculations exploit the method proposed previously by the authors and based on the instant-form Poincaré invariant approach to pions, considered as quark-antiquark systems. This model has predicted with surprising accuracy the values of $F_{\pi }(Q^2)$, which were measured later in JLab experiments. The results are almost independent from the form of wave function. The pion mean square radius $\langle r_{\pi }^2\rangle$ and the decay constant $f_{\pi }$ also agree with experimental values. The model gives powerlike asymptotic behavior of $F_{\pi }(Q^2)$ at high momentum transfer in agreement with QCD predictions.

Photoneutron cross sections were measured for ${}^{117}\mathrm{Sn}$ and ${}^{116}\mathrm{Sn}$ near the neutron thresholds at $6.94$ and $9.56$ MeV, respectively, with quasi-monochromatic laser-Compton scattering $\gamma$ rays. The ${}^{117}\mathrm{Sn}$ cross section, which is strongly enhanced near the low threshold, provides evidence for the presence of extra $\gamma$ strength in the low-energy tail of the giant dipole resonance. A coherent analysis of the photoneutron data for ${}^{117}\mathrm{Sn}$ together with the neutron capture on ${}^{116}\mathrm{Sn}$ shows that the $\gamma$-ray strength function is balanced in the photoneutron and neutron capture channels in terms of the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation model of $E1$ strength combined with a pygmy $E1$ resonance at $8.5$ MeV. The high-energy part of the pygmy resonance is also suggested in the photoneutron cross section for ${}^{116}\mathrm{Sn}$.

Half-lives $T_{1/2}^{2\nu }$ for two-neutrino positron double-$\beta$ decay modes ${\beta }^{+}$ EC/ECEC are calculated for ${}^{74}\mathrm{Se}$, a nucleus of current experimental interest, using the deformed shell model based on Hartree-Fock states and employing a modified Kuo interaction in (${}^2{p}_{3/2}$, ${}^1{f}_{5/2}$, ${}^2{p}_{1/2}$, ${}^1{g}_{9/2}$) space. The calculated half-life for the ECEC mode is $~{10}^{26}\mathrm{yr}$, and it may be possible to observe this in future experiments.

Measurements of prompt Doppler-corrected deexcitation $\gamma$ rays from uniquely identified fragments formed in fusion-fission reactions of the type ${}^{12}\mathrm{C}({}^{238}\mathrm{U},{}^{134}\mathrm{Xe})\mathrm{Ru}$ are reported. The fragments were identified in both $A$ and $Z$ using the variable-mode, high-acceptance magnetic spectrometer VAMOS. States built on the characteristic neutron configurations forming high-spin isomers ($7^{-}$ and ${10}^{+}$) in ${}^{134}\mathrm{Xe}$ are presented and compared with the predictions of shell-model calculations using a new effective interaction in the region of $Z⩾50$ and $N⩽82$.

SU$(N_c)$ color-singlet restriction, along with flavor and spin symmetry, on a thermal partonic ensemble is shown to recombine the partons with internal color structure into color-singlet multiquark clusters, which can be identified with various hadronic modes at a given temperature. This can provide a possible basis for a recombination model for hadronization of quark-gluon plasma. This also leads to a natural explanation for the ratio of (anti)protons to pions and the quark number scaling of the elliptic flow coefficient in relativistic heavy-ion collisions.

Excited states in ${}^{163}\mathrm{Ta}$ have been identified for the first time using the ${}^{106}\mathrm{Cd}({}^{60}\mathrm{Ni},3p)$ fusion evaporation reaction. $\gamma$ rays were detected using the JUROGAM $\gamma$-ray spectrometer and recoil discrimination was achieved using the recoil ion transport unit (RITU) gas-filled separator in conjunction with the GREAT spectrometer situated at the focal plane of the RITU. The yrast states are assigned to a strongly coupled rotational band based on a $\pi h_{11/2}$ configuration. This structure exhibits large signature splitting at low spins that disappears after the paired band crossing because of the alignment of a pair of $i_{13/2}$ neutrons. This effect is ascribed to triaxial shape changes induced by the core-polarizing properties of the deformation-aligned $h_{11/2}$ proton and the rotation-aligned $i_{13/2}$ neutrons. Two additional strongly coupled band structures have been established and are discussed in terms of octupole-vibrational and two-quasiparticle excitations built on the yrast structure. The experimental results are compared with predictions from cranked-shell-model and total-Routhian-surface calculations.

$\alpha$-particle evaporation energy spectra have been measured as a function of $\gamma$-ray fold for various target-projectile systems leading to residual nuclei in the range of $Z~70$ and $A~180$ with excitation energy of 30–40 MeV. The inverse level-density parameter $K$ was determined for various nuclei by comparing the high-energy part of the $\alpha$-particle evaporation spectra with PACE2 predictions. It is observed that the inverse level-density parameter remains constant for all systems studied in this work within statistical errors in the angular momentum range of 15–30 $\hslash$. The fold-gated $\alpha$-particle energy spectra in these systems are well reproduced by the PACE2 code with a level-density parameter value of $A/(8.2\pm 1.1)$ MeV${}^{-1}$.

${}^{230}\mathrm{U}$ and its daughter nuclide ${}^{226}\mathrm{Th}$ are novel therapeutic nuclides for application in targeted $\alpha$ therapy of cancer. We investigated the feasibility of producing ${}^{230}\mathrm{U}/{}^{226}\mathrm{Th}$ via deuteron irradiation of ${}^{231}\mathrm{Pa}$ according to the reaction ${}^{231}\mathrm{Pa}(d,3n){}^{230}\mathrm{U}$. The experimental excitation function for a deuteron-induced reaction on ${}^{231}\mathrm{Pa}$ is reported for the first time. Cross sections were measured using thin targets of ${}^{231}\mathrm{Pa}$ prepared by electrodeposition and ${}^{230}\mathrm{U}$ yields were analysed using $\alpha$ spectrometry. Beam energies were calculated from measured beam orbits and compared with the values obtained via monitor reactions on aluminium foils using high-resolution $\gamma$ spectrometry and IAEA recommended cross sections. Beam intensities were determined using a beam current integrator. The experimental cross sections are in excellent agreement with model calculations allowing for deuteron breakup using the EMPIRE 3 code. According to thick-target yields calculated from the experimental excitation function, the reaction ${}^{231}\mathrm{Pa}(d,3n){}^{230}\mathrm{U}$ allows the production of ${}^{230}\mathrm{U}/{}^{226}\mathrm{Th}$ at moderate levels.

Heavy-ion collisions often produce fusion barrier distributions with structures displaying a fingerprint of couplings to highly collective excitations. Similar distributions can be obtained from large-angle quasielastic scattering, although in this case, the role of the many weak direct-reaction channels is unclear. For ${}^{20}\mathrm{Ne}+{}^{90}\mathrm{Zr}$, we have observed the barrier structures expected for the highly deformed neon projectile; however, for ${}^{20}\mathrm{Ne}+{}^{92}\mathrm{Zr}$, we find significant extra absorption into a large number of noncollective inelastic channels. This leads to smearing of the barrier distribution and a consequent reduction in the “resolving power” of the quasielastic method.

Combined data from four fusion-evaporation reaction experiments were utilized to investigate deformed and superdeformed structures in ${}_{30}^{62}{\mathrm{Zn}}_{32}$. Combination of the Gammasphere $\gamma$-ray spectrometer and ancillary particle detection systems allowed for the connection of rotational bands to well-known, low-lying excited states in ${}^{62}\mathrm{Zn}$, as well as spectroscopy of discrete high-spin states reaching excitation energies of $E_x=42.5$ MeV. Four well- or superdeformed bands in ${}^{62}\mathrm{Zn}$ are characterized and described by means of cranked Nilsson-Strutinsky calculations.

Hartree-Fock-Bogoliubov calculations of hot fission in ${}^{240}\mathrm{Pu}$ have been performed with a newly implemented code that uses the D1S finite-range effective interaction. The hot-scission line is identified in the quadrupole-octupole-moment coordinate space. Fission-fragment shapes are extracted from the calculations. A benchmark calculation for ${}^{226}\mathrm{Th}$ is obtained and compared with results in the literature. In addition, technical aspects of the use of HFB calculations for fission studies are examined in detail. In particular, the identification of scission configurations, the sensitivity of near-scission calculations to the choice of collective coordinates in the HFB iterations, and the formalism for the adjustment of collective-variable constraints are discussed. The power of the constraint-adjustment algorithm is illustrated with calculations near the critical scission configurations with up to seven simultaneous constraints.

We demonstrate how the separation of the total energy of a self-bound system into a functional of the internal one-body Fermionic density and a function of an arbitrary wave vector describing the center-of-mass kinetic energy can be used to set up an “internal” Kohn-Sham scheme.

The first spectroscopic study for the $\beta$ decay of ${}^{21}\mathrm{N}$ is carried out based on $\beta –n$, $\beta –\gamma$, and $\beta –n–\gamma$ coincidence measurements. The neutron-rich ${}^{21}\mathrm{N}$ nuclei are produced by the fragmentation of the $E/A=68.8$ MeV ${}^{26}\mathrm{Mg}$ primary beam on a thick ${}^9\mathrm{Be}$ target and are implanted into a thin plastic scintillator that also plays the role of $\beta$ detector. The time of flight of the emitted neutrons following the $\beta$ decay are measured by the surrounding neutron sphere and neutron wall arrays. In addition, four clover germanium detectors are used to detect the $\beta$-delayed $\gamma$ rays. Thirteen new $\beta$-delayed neutron groups are observed with a total branching ratio of $90.5\pm 4.2\%$. The half-life for the $\beta$ decay of ${}^{21}\mathrm{N}$ is determined to be $82.9\pm 7.5$ ms. The level scheme of  ${}^{21}\mathrm{O}$ is deduced up to about 9 MeV excitation energy. The experimental results for the $\beta$ decay of ${}^{21}\mathrm{N}$ are compared to the shell-model calculations.