We study the production and dynamics of heavy quarks in the parton cascade model for relativistic heavy ion collisions. The model is motivated by the QCD parton picture and describes the dynamics of an ultrarelativistic heavy ion collision in terms of cascading partons which undergo scattering and multiplication while propagating. We focus on the dynamics of charm quark production and evolution in $p+p$ and Au + Au collisions for several different interaction scenarios, viz., collisions only between primary partons without radiation of gluons, multiple collisions without radiation of gluons, and multiple collisions with radiation of gluons, allowing us to isolate the contributions of parton rescattering and radiation to charm production. We also discuss results of an eikonal approximation of the collision which provides a valuable comparison with minijet calculations and clearly brings out the importance of multiple collisions.

Background: Deuteron induced reactions are widely used to probe nuclear structure and astrophysical information. Those ($d,p$) reactions may be viewed as three-body reactions and described with Faddeev techniques.

Purpose: Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. However, it needs to be demonstrated that their solution based on separable interactions agrees exactly with solutions based on nonseparable forces.

Methods: Momentum space Faddeev equations are solved with nonseparable and separable forces as coupled integral equations.

Results: The ground state of ${}^6\mathrm{Li}$ is calculated via momentum space Faddeev equations using the CD-Bonn neutron-proton force and a Woods-Saxon type neutron(proton)-${}^4\mathrm{He}$ force. For the latter the Pauli-forbidden $S$-wave bound state is projected out. This result is compared to a calculation in which the interactions in the two-body subsystems are represented by separable interactions derived in the Ernst-Shakin-Thaler (EST) framework.

Conclusions: We find that calculations based on the separable representation of the interactions and the original interactions give results that agree to four significant figures for the binding energy, provided that energy and momentum support points of the EST expansion are chosen independently. The momentum distributions computed in both approaches also fully agree with each other.

We present measurements of the elliptic flow ($v_2$) as a function of transverse momentum ($p_T$), pseudorapidity ($\eta$), and centrality in $d+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$, 62.4, 39, and 19.6 GeV. The beam-energy scan of $d+\mathrm{Au}$ collisions provides a testing ground for the onset of flow signatures in small collision systems. We measure a nonzero $v_2$ signal at all four collision energies, which, at midrapidity and low $p_T$, is consistent with predictions from viscous hydrodynamic models. Comparisons with calculations from parton transport models (based on the ampt Monte Carlo generator) show good agreement with the data at midrapidity to forward ($d$-going) rapidities and low $p_T$. At backward (Au-going) rapidities and $p_T>1.5\mathrm{GeV}/c$, the data diverges from ampt calculations of $v_2$ relative to the initial geometry, indicating the possible dominance of nongeometry related correlations, referred to as nonflow. We also present measurements of the charged-particle multiplicity ($d{N}_{\mathrm{ch}}/d\eta$) as a function of $\eta$ in central $d+\mathrm{Au}$ collisions at the same energies. We find that in $d+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV the $v_2$ scales with $d{N}_{\mathrm{ch}}/d\eta$ over all $\eta$ in the PHENIX acceptance. At $\sqrt{s_{\mathit{NN}}}=62.4$, and 39 GeV, $v_2$ scales with $d{N}_{\mathrm{ch}}/d\eta$ at midrapidity and forward rapidity, but falls off at backward rapidity. This departure from the $d{N}_{\mathrm{ch}}/d\eta$ scaling may be a further indication of nonflow effects dominating at backward rapidity.

Background: Measurements of the neutron charge form factor, $G_E^n$, are challenging because the neutron has no net charge. In addition, measurements of the neutron form factors must use nuclear targets which require accurately accounting for nuclear effects. Extracting $G_E^n$ with different targets and techniques provides an important test of our handling of these effects.

Purpose: The goal of the measurement was to use an inclusive asymmetry measurement technique to extract the neutron charge form factor at a four-momentum transfer of $1{\left(\mathrm{GeV}/\mathrm{c}\right)}^2$. This technique has very different systematic uncertainties than traditional exclusive measurements and thus serves as an independent check of whether nuclear effects have been taken into account correctly.

Method: The inclusive quasielastic reaction ${}^3\overrightarrow{\mathrm{He}}(\vec{e},e^{\prime })$ was measured at Jefferson Laboratory. The neutron electric form factor, $G_E^n$, was extracted at $Q^2=0.98{\left(\mathrm{GeV}/\mathrm{c}\right)}^2$ from ratios of electron-polarization asymmetries measured for two orthogonal target spin orientations. This $Q^2$ is high enough that the sensitivity to $G_E^n$ is not overwhelmed by the neutron magnetic contribution, and yet low enough that explicit neutron detection is not required to suppress pion production.

Results: The neutron electric form factor, $G_E^n$, was determined to be $0.0414\pm 0.0077\left(\text{stat}\right)\pm 0.0022\left(\text{syst}\right)$, providing the first high-precision inclusive extraction of the neutron's charge form factor.

Conclusions: The use of the inclusive quasielastic ${}^3\overrightarrow{\mathrm{He}}(\vec{e},e^{\prime })$ with a four-momentum transfer near $1{\left(\mathrm{GeV}/\mathrm{c}\right)}^2$ has been used to provide a unique measurement of $G_E^n$. This new result provides a systematically independent validation of the exclusive extraction technique results and implies that the nuclear corrections are understood. This is contrary to the proton form factor where asymmetry and differential cross section measurements have been shown to have large systematic differences.

We used the world data on the kaon form factor to extract the transverse kaon charge density using a dispersion integral of the imaginary part of the kaon form factor in the timelike region. Our analysis includes recent data from $e^{+}{e}^{-}$ annihiliation measurements extending the kinematic reach of the data into the region of high momentum transfers conjugate to the region of short transverse distances. To calculate the transverse density we created a superset of both timelike and spacelike data and developed an empirical parameterization of the kaon form factor. The spacelike set includes two new data points we extracted from existing cross section data. We estimate the uncertainty on the resulting transverse density to be 5% at $b=0.025$ fm and significantly better at large distances. New kaon data planned with the 12 GeV Jefferson Lab may have a significant impact on the charge density at distances of $b<0.1$ fm.

The cross sections of elastic scattering and fusion of identical heavy ions with arbitrary spin, $s$ are derived. Applications to several light heavy ions at near-barrier energies are made. It is found that the transverse isotropy; namely, the flat angular distribution which sets in at a critical value of the energy, becomes less pronounced with higher values of the spin. The oscillations in energy in the fusion cross section was found to go as $1/(2s+1)$. A similar factor is found in the angle-oscillating term in the elastic-scattering cross section.

We developed a four-dimensional (4D) Langevin model, which can treat the deformation of each fragment independently and applied it to low-energy fission of ${}^{236}\mathrm{U}$, the compound system of the reaction $n+{}^{235}\mathrm{U}$. The potential energy is calculated with the deformed two-center Woods-Saxon (TCWS) and the Nilsson-type potential with the microscopic energy corrections following the Strutinsky method and BCS pairing. The transport coefficients are calculated by macroscopic prescriptions. It turned out that the deformation for the light and heavy fragments behaves differently, showing a sawtooth structure similar to that of the neutron multiplicities of the individual fragments $\nu \left(A\right)$. Furthermore, the measured total kinetic energy $\mathrm{TKE}\left(A\right)$ and its standard deviation are reproduced fairly well by the 4D Langevin model based on the TCWS potential in addition to the fission fragment mass distributions. The developed model allows a multiparametric correlation analysis among, e.g., the three key fission observables, mass, TKE, and neutron multiplicity, which should be essential to elucidate several longstanding open problems in fission such as the sharing of the excitation energy between the fragments.

We analyzed the total kinetic energy (TKE) of fission fragments with three-dimensional Langevin calculations for a series of actinides and Fm isotopes at various excitation energies. This allowed us to establish systematic trends of TKE with $Z^2/A^{1/3}$ of the fissioning system and as a function of excitation energy. In the mass-energy distributions of fission fragments we see the contributions from the standard, super-long, and super-short (in the case of ${}^{258}\mathrm{Fm})$ fission modes. For the fission fragments mass distribution of ${}^{258}\mathrm{Fm}$ we obtained a single peak mass distribution. The decomposition of TKE into the prescission kinetic energy and Coulomb repulsion showed that decrease of TKE with growing excitation energy is accompanied by a decrease of prescission kinetic energy. It was also found that transport coefficients (friction and inertia tensors) calculated by a microscopic model and by macroscopic models give drastically different behaviors of TKE as a function of excitation energy. The results obtained with microscopic transport coefficients are much closer to experimental data than those calculated with macroscopic ones.

The relativistic effective mass $M^{*}$ and Fermi momentum $k_F$ are important ingredients in the determination of the nuclear equation of state, but they have rarely been extracted from experimental data below saturation density where translationally invariant nuclear matter becomes unstable against clusterization into the existing atomic nuclei. Using a novel kind of superscaling analysis of the quasielastic cross-section electron scattering data involving a suitable selection criterion and ${}^{12}\mathrm{C}$ as a reference nucleus, the global scaling properties of the resulting set of data for 21 nuclei ranging from ${}^2\mathrm{H}$ to ${}^{238}\mathrm{U}$ are then analyzed. We find that a subset of a third of the about 20000 data approximately scales to an universal superscaling function with a more constrained uncertainty band than just the reference ${}^{12}\mathrm{C}$ case and provides $M^{*}$ as a function of $k_F$.

We present the results of three-dimensional femtoscopic analyses for charged and neutral kaons recorded by ALICE in Pb-Pb collisions at $\sqrt{s_{\mathit{NN}}}=2.76$ TeV. Femtoscopy is used to measure the space-time characteristics of particle production from the effects of quantum statistics and final-state interactions in two-particle correlations. Kaon femtoscopy is an important supplement to that of pions because it allows one to distinguish between different model scenarios working equally well for pions. In particular, we compare the measured three-dimensional kaon radii with a purely hydrodynamical calculation and a model where the hydrodynamic phase is followed by a hadronic rescattering stage. The former predicts an approximate transverse mass ($m_{\mathrm{T}}$) scaling of source radii obtained from pion and kaon correlations. This $m_{\mathrm{T}}$ scaling appears to be broken in our data, which indicates the importance of the hadronic rescattering phase at LHC energies. A $k_{\mathrm{T}}$ scaling of pion and kaon source radii is observed instead. The time of maximal emission of the system is estimated by using the three-dimensional femtoscopic analysis for kaons. The measured emission time is larger than that of pions. Our observation is well supported by the hydrokinetic model predictions.

Within an isospin- and momentum-dependent transport model for nuclear reactions at intermediate energies, we investigate the interplay of the nucleon-nucleon short-range correlations (SRCs) and nuclear symmetry energy $E_{\text{sym}}\left(\rho \right)$ on hard-photon spectra in collisions of several Ca isotopes on ${}^{112}\mathrm{Sn}$ and ${}^{124}\mathrm{Sn}$ targets at a beam energy of 45 MeV/nucleon. It is found that over the whole spectra of hard photons studied, effects of the SRCs overwhelm those owing to the $E_{\text{sym}}\left(\rho \right)$. The energetic photons come mostly from the high-momentum tails (HMTs) of single-nucleon momentum distributions in the target and projectile. Within the neutron-proton dominance model of SRCs based on the consideration that the tensor force acts mostly in the isosinglet and spin-triplet nucleon-nucleon interaction channel, there are equal numbers of neutrons and protons, thus a zero isospin asymmetry in the HMTs. Therefore, experimental measurements of the energetic photons from heavy-ion collisions at Fermi energies have the great potential to help us better understand the nature of SRCs without any appreciable influence by the uncertain $E_{\text{sym}}\left(\rho \right)$. These measurements will be complementary to but also have some advantages over the ongoing and planned experiments using hadronic messengers from reactions induced by high-energy electrons or protons. Because the underlying physics of SRCs and $E_{\text{sym}}\left(\rho \right)$ are closely correlated, a better understanding of the SRCs will, in turn, help constrain the nuclear symmetry energy more precisely in a broad density range.

Background: An accurate determination of the core-crust transition is necessary in the modeling of neutron stars for astrophysical purposes. The transition is intimately related to the isospin dependence of the nuclear force at low baryon densities.

Purpose: To study the symmetry energy and the core-crust transition in neutron stars using the finite-range Gogny nuclear interaction and to examine the deduced crustal thickness and crustal moment of inertia.

Methods: The second-, fourth-, and sixth-order coefficients of the Taylor expansion of the energy per particle in powers of the isospin asymmetry are analyzed for Gogny forces. These coefficients provide information about the departure of the symmetry energy from the widely used parabolic law. The neutron star core-crust transition is evaluated by looking at the onset of thermodynamical instability of the liquid core. The calculation is performed with the exact Gogny equation of state (EoS) (i.e., the Gogny EoS with the full isospin dependence) for the $\beta$-equilibrated matter of the core, and also with the Taylor expansion of the Gogny EoS in order to assess the influence of isospin expansions on locating the inner edge of neutron star crusts.

Results: The properties of the core-crust transition derived from the exact EoS differ from the predictions of the Taylor expansion even when the expansion is carried through sixth order in the isospin asymmetry. Gogny forces, using the exact EoS, predict the ranges $0.094{\text{fm}}^{-3}\lesssim {\rho }_t\lesssim 0.118{\text{fm}}^{-3}$ for the transition density and $0.339\text{MeV}{\text{fm}}^{-3}\lesssim P_t\lesssim 0.665\text{MeV}{\text{fm}}^{-3}$ for the transition pressure. The transition densities show an anticorrelation with the slope parameter $L$ of the symmetry energy. The transition pressures are not found to correlate with $L$. Neutron stars obtained with Gogny forces have maximum masses below $1.74M_{\odot }$ and relatively small moments of inertia. The crustal mass and moment of inertia are evaluated and comparisons are made with the constraints from observed glitches in pulsars.

Conclusions: The finite-range exchange contribution of the nuclear force, and its associated nontrivial isospin dependence, is key in determining the core-crust transition properties. Finite-order isospin expansions do not reproduce the core-crust transition results of the exact EoS. The predictions of the Gogny D1M force for the stellar crust are overall in broad agreement with those obtained using the Skyrme-Lyon EoS.

Background: Neutron capture cross sections are essential to understanding the astrophysical $s$ and $r$ processes, the modeling of nuclear reactor design and performance, and for a wide variety of nuclear forensics applications. Often, cross sections are needed for nuclei where experimental measurements are difficult. Enormous effort, over many decades, has gone into attempting to develop sophisticated statistical reaction models to predict these cross sections. Such work has met with some success but is often unable to reproduce measured cross sections to better than $40\%$, and has limited predictive power, with predictions from different models rapidly differing by an order of magnitude a few nucleons from the last measurement.

Purpose: To develop a new approach to predicting neutron capture cross sections over broad ranges of nuclei that accounts for their values where known and which has reliable predictive power with small uncertainties for many nuclei where they are unknown.

Methods: Experimental neutron capture cross sections were compared to empirical mass observables in regions of similar structure.

Results: We present an extremely simple method, based solely on empirical mass observables, that correlates neutron capture cross sections in the critical energy range from a few keV to a couple hundred keV. We show that regional cross sections are compactly correlated in medium and heavy mass nuclei with the two-neutron separation energy. These correlations are easily amenable to predict unknown cross sections, often converting the usual extrapolations to more reliable interpolations. It almost always reproduces existing data to within $25\%$ and estimated uncertainties are below about $40\%$ up to 10 nucleons beyond known data.

Conclusions: Neutron capture cross sections display a surprisingly strong connection to the two-neutron separation energy, a nuclear structure property. The simple, empirical correlations uncovered provide model-independent predictions of neutron capture cross sections, extending far from stability, including for nuclei of the highest sensitivity to $r$-process nucleosynthesis.

The interacting boson-fermion model (IBFM), with parameters determined from the microscopic Hartree-Fock-Bogoliubov (HFB) approximation, based on the parametrization D1M of the Gogny energy density functional, is employed to study the structural evolution in odd-mass $\gamma$-soft nuclei. The deformation energy surfaces of even-even nuclei, single-particle energies, and occupation probabilities of the corresponding odd-mass systems have been obtained within the constrained HFB approach. Those building blocks are then used as a microscopic input to build the IBFM Hamiltonian. The coupling constants of the boson-fermion interaction terms are taken as free parameters, fitted to reproduce experimental low-lying spectra. The diagonalization of the IBFM Hamiltonian provides the spectroscopic properties for the studied odd-mass nuclei. The procedure has been applied to compute low-energy excitation spectra and electromagnetic transition rates, in the case of the $\gamma$-soft odd-mass systems ${}^{129-137}\mathrm{Ba}$, ${}^{127-135}\mathrm{Xe}$, ${}^{129-137}\mathrm{La}$, and ${}^{127-135}\mathrm{Cs}$. The calculations provide a reasonable agreement with the available experimental data and agree well with previous results based on the relativistic mean-field approximation.

Within the framework of a simple macroscopic model, the ternary-fragmentation-driving potential energies of ${}^{252}\mathrm{Cf}$ are studied. In this work, all possible ternary-fragment combinations of ${}^{252}\mathrm{Cf}$ are generated by the use of atomic mass evaluation-2016 (AME2016) data and these combinations are minimized by using a two-dimensional minimization approach. This minimization process can be done in two ways: (i) with respect to proton numbers ($Z_1$, $Z_2$, $Z_3$) and (ii) with respect to neutron numbers ($N_1$, $N_2$, $N_3$) of the ternary fragments. In this paper, the driving potential energies for the ternary breakup of ${}^{252}\mathrm{Cf}$ are presented for both the spherical and deformed as well as the proton-minimized and neutron-minimized ternary fragments. From the proton-minimized spherical ternary fragments, we have obtained different possible ternary configurations with a minimum driving potential, in particular, the experimental expectation of Sn + Ni + Ca ternary fragmentation. However, the neutron-minimized ternary fragments exhibit a driving potential minimum in the true-ternary-fission (TTF) region as well. Further, the $Q$-value energy systematics of the neutron-minimized ternary fragments show larger values for the TTF fragments. From this, we have concluded that the TTF region fragments with the least driving potential and high $Q$ values have a strong possibility in the ternary fragmentation of ${}^{252}\mathrm{Cf}$. Further, the role of ground-state deformations (${\beta }_2$, ${\beta }_3$, ${\beta }_4$, and ${\beta }_6$) in the ternary breakup of ${}^{252}\mathrm{Cf}$ is also studied. The deformed ternary fragmentation, which involves $Z_3=12–19$ fragments, possesses the driving potential minimum due to the larger oblate deformations. We also found that the ground-state deformations, particularly ${\beta }_2$, strongly influence the driving potential energies and play a major role in determining the most probable fragment combinations in the ternary breakup of ${}^{252}\mathrm{Cf}$.

The experimental data taken from both Drell-Yan and deep-inelastic scattering experiments suggest a sign change in $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ flavor asymmetry in the proton at large values of momentum fraction $x$. In this work, we present a phenomenological study of $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ flavor asymmetry. First, we extract the $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ distribution using the more recent data from the BONuS experiment at Jefferson Lab on the ratio of neutron to proton structure functions, $F_2^n/F_2^p$, and show that it undergoes a sign change and becomes negative at large values of momentum fraction $x$, as expected. The stability and reliability of our obtained results are examined by including target mass corrections as well as higher twist terms which are particularly important in the large-$x$ region at low $Q^2$. Then, we calculate the $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ distribution using the Brodsky-Hoyer-Peterson-Sakai model and show that if one chooses a mass for the down quark smaller than the one for the up quark it leads to a better description for the Fermilab E866 data. To prove this claim, we determine the masses of down and up sea quarks by fitting to the available and up-to-date experimental data for the $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ distribution. In this respect, unlike the previous theoretical studies, we have shown that this distribution has a sign change at $x>0.3$ after evolution to the scale of available experimental data.

Excited states of the $N=32$ nucleus ${}^{54}\mathrm{Ti}$ have been studied, via both inverse-kinematics proton scattering and one-neutron knockout from ${}^{55}\mathrm{Ti}$ by a liquid hydrogen target, using the GRETINA $\gamma$-ray tracking array. Inelastic proton-scattering cross sections and deformation lengths have been determined. A low-lying octupole state has been tentatively identified in ${}^{54}\mathrm{Ti}$ for the first time. A comparison of $(p,p^{\prime })$ results on low-energy octupole states in the neutron-rich Ca and Ti isotopes with the results of random phase approximation calculations demonstrates that the observed systematic behavior of these states is unexpected.

In high energy heavy-ion collisions, the degrees of freedom at the very early stage can be effectively represented by strong classical gluonic fields within the color glass condensate framework. As the system expands, the strong gluonic fields eventually become weak such that an equivalent description using the gluonic particle degrees of freedom starts to become valid. In this paper, the spectrum of these gluonic particles is reexamined by solving the classical Yang-Mills equations semianalytically, with the solutions having the form of power series expansions in the proper time. A different formula for the gluon spectrum, which is consistent with energy density during the whole time evolution, is proposed. One finds that the chromoelectric fields have larger contributions to the gluon spectrum than the chromomagnetic fields do. Furthermore, the large momentum modes take less time to reach the weak-field regime while smaller momentum modes take more time. The resulting functional form of the gluon spectrum is exponential in nature and the spectrum is close to a thermal distribution, with effective temperatures around $0.6Q_s$ to $0.9Q_s$ late in the glasma evolution. The sensitiveness of the gluon spectrum to the infrared and the ultraviolet cutoffs is discussed.

Parity-violating and time-reversal-violating (PVTV) pion-nucleon couplings govern the magnitude of long-range contributions to nucleon and atomic electric-dipole moments. When these couplings arise from chiral-symmetry-breaking charge-parity-violating (CP-violating) operators, such as the QCD $\theta$ term or quark chromoelectric dipole moments, one may relate hadronic matrix elements entering the PVTV couplings to nucleon and pion mass shifts by exploiting the corresponding chiral transformation properties at leading order in the chiral expansion. We compute the higher order contributions to the lowest order relations arising from chiral loops and next-to-next-to leading order operators. We find that, for the QCD $\theta$ term, the higher order contributions are analytic in the quark masses, while for the quark chromoelectric dipole moments and chiral-symmetry-breaking four-quark operators, the matching relations also receive nonanalytic corrections. Numerical estimates suggest that, for the isoscalar PVTV pion-nucleon coupling, the higher order corrections may be as large as $\sim 20\%$, while for the isovector coupling, more substantial corrections are possible.