A recoil-distance Doppler shift experiment has been performed using the ${}^{102}\mathrm{Pd}({}^{19}\mathrm{F},p2n$) reaction at a beam energy of 73 MeV to measure the lifetime of excited states in ${}^{118}\mathrm{Xe}$. The differential decay-curve method using $\gamma \gamma$ coincidences and a gating procedure that allows to extract the lifetime without feeding assumptions has been employed. The lifetimes obtained for the yrast states up to spin-parity $8^{+}$ are compared with interacting boson model calculations and ${}^{118}\mathrm{Xe}$ can be classified as a transitional nucleus between the spherical and a deformed shape. Systematics of the $B\left(E2\right)$ values for the $2^{+}\to 0^{+}$ and $4^{+}\to 2^{+}$ transitions in the isotopic chains of tin, tellurium and xenon are presented. It is proposed that a “critical point” exists at which the $B(E2;4^{+}\to 2^{+})/B(E2;2^{+}\to 0^{+})$ ratio drops to unity for lower neutron numbers within the isotopic chain. The position of the “critical point” varies with proton number, i.e., it is presumed to be located at the same mass number $A=114$ in the Sn, Te, and Xe isotopes.

Using a semiclassical dynamical model that combines a classical trajectory model with stochastic breakup with a dynamical fragmentation theory treatment of two-body clusterization and decay of a projectile, results are presented for ${}^{20}\mathrm{Ne}$-induced incomplete fusion reactions for the production of superheavy elements. Targets include ${}^{247,248,250}\mathrm{Cm}$ and ${}^{251,252,254}\mathrm{Cf}$, and results include angular, excitation energy, and angular momentum distributions in addition to total integrated cross sections for heavy incomplete fusion products. The results show that at Coulomb energies, the studied Cf isotopes are generally the more favorable choice of target over the studied Cm isotopes for the production of ‘colder’ and more stable ${}^{263}\mathrm{Lr}$, ${}^{263,264,266}\mathrm{Rf}$, and ${}^{265}\mathrm{Db}$ isotopes through the incomplete fusion mechanism. Also presented are evaporation residue cross sections for the dominant primary incomplete fusion products of each of the six reactions: ${}^{263,264,266}\mathrm{Rf}$ and ${}^{267,268,270}\mathrm{Sg}$, as well as for the primary incomplete fusion products ${}^{269,270,272}\mathrm{Bh}$.

The standard relativistic mean field model, extended with $\sigma -\delta$ meson interaction, is applied to study neutron star (NS) properties. In the equation of state including such interaction, the phase transition occurs in the core region of NSs. The phase transition leads to multilayer neutron star structure and to the softening of the equation of state (EOS) in a moderate range of densities. Such an EOS, consequently, makes the neutron star more compact without reducing its maximum mass. The star properties obtained are in very good agreement with the most recent observational data from the LIGO/Virgo gravitational wave detectors and x-ray observations of NICER.

The study of nuclei in the yet-unexplored, very neutron-rich, mid- to heavy-mass region of the nuclear chart, comprising perhaps half of all nuclei predicted to exist, is leading to new and/or upgraded facilities, as well as to research into the underlying production processes. In the present study, the usefulness of the two-step scheme, an alternate method to produce very neutron-rich nuclei, by a combination of an isotope-separation online (ISOL) system as a first step, and in-beam fragmentation of re-accelerated radioactive isotopes (RIs) as a second step, was investigated with a ${}^{132}\mathrm{Sn}$ beam. Very neutron-rich RIs around the neutron-rich neutron number $N=82$ region were produced from the 278-MeV/nucleon ${}^{132}\mathrm{Sn}$ beam impinging on a 5.97-mm Be target, and their production cross sections were measured. Yields were then estimated for the two-step scheme with the ${}^{132}\mathrm{Sn}$ beam relative to the ones by a one-step scheme, in-flight fission of a ${}^{238}\mathrm{U}$ beam, for 1-MW proton and ${}^{238}\mathrm{U}$ beams at respective RI-beam facilities. This comparison suggests that the two-step scheme with the ${}^{132}\mathrm{Sn}$ beam provides yields $>40$-times higher than those with the one-step scheme for the very neutron-rich $N=82$ region. Moreover, by using various RI beams over the nuclear chart from ISOL, certain kinds of very neutron-rich RIs around the supernova $r$-process path can be produced with greater yields than by the one-step approach.

The contribution of a three-nucleon (3N) force, acting between the neutron and proton in the incoming deuteron with a target nucleon, to the deuteron-target potential in the entrance channel of the $A(d,p)B$ reaction has been calculated within the adiabatic distorted wave approximation (ADWA). Four different 3N interaction sets from local chiral effective field theory ($\chi \mathrm{EFT}$) at next-to-next-to-leading order were used. Strong sensitivity of the adiabatic deuteron-target potential to the choice of the 3N force format has been found, which originates from the enhanced sensitivity to the short-range physics of nucleon-nucleon and 3N interactions in the ADWA. Such a sensitivity is reduced when a Watanabe folding model is used to generate the $d\text{−}A$ potential instead of ADWA. The impact of the 3N force contribution on $(d,p)$ cross sections depends on assumptions made about the $p\text{−}A$ and $n\text{−}A$ optical potentials used to calculate the distorted $d\text{−}A$ potential in the entrance channel. It is different for local and nonlocal optical potentials and depends on whether the induced three-body force arising due to neglect of target excitations is included or not.

The effects of cluster correlations have been studied in the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reaction at 50 MeV/nucleon, using three antisymmetrized molecular dynamics (AMD) models, the AMD (AMD/D) without any additional cluster correlations, AMD/D-COALS with nucleon correlations based on a coalescence prescription for light cluster formations with $A\le 4$, and AMD-cluster with an extended cluster correlation in two-nucleon collision processes and a special treatment for intermediate fragment formation with $A\le 9$. The angular distributions and energy spectra of fragments have been simulated and compared with the available experimental data. It is found that the cluster correlations take a crucial role to describe the productions of light charged particles (LCPs) and intermediate mass fragments (IMFs), and the AMD-cluster studied here provides a consistent overall reproduction of the experimental data. It is also shown that the significant effects of the secondary decay processes are involved for the fragment production besides the dynamical productions in the AMD stage. Detailed LCP and IMF production mechanisms involved in the intermediate energy heavy ion collisions are discussed.

The ground state band of the even ${}^{118–134}\mathrm{Ba}$ and ${}^{142–150}\mathrm{Ba}$ isotopes, which extend over two neutron major shells, and the quasi-$\gamma$ band, in the neutron-deficient Ba region, have been investigated in the framework of the IBA-2 model. All available spectroscopic data concerning these isotopes have been compared to the calculated values. It has been found that the two bands have different symmetry in the proton and neutron degrees of freedom. Their structure evolution, as a function of the neutron number, and the decay properties of the quasi-$\gamma$ band have been studied in detail.

The excitation energy of deformed intruder states (specifically the 2p2h bandhead) as a function of proton number $Z$ along $N=20$ is of interest both in terms of better understanding the evolution of nuclear structure between spherical ${}^{40}\mathrm{Ca}$ and the Island of Inversion nuclei, and for benchmarking theoretical descriptions in this region. At the center of the $N=20$ Island of Inversion, the $n\mathrm{p}n\mathrm{h}$ (where $n=2,4,6$) neutron excitations across a diminished $N=20$ gap result in deformed and collective ground states, as observed in ${}^{32}\mathrm{Mg}$. In heavier isotones, $n\mathrm{p}n\mathrm{h}$ excitations do not dominate in the ground states but are present in the relatively low-lying level schemes. With the aim of identifying the expected $2\mathrm{p}2\mathrm{h}\otimes {\mathrm{s}}_{1/2^{+}}$ state in ${}^{35}\mathrm{P}$, the only $N=20$ isotone for which the neutron 2p2h excitation bandhead has not yet been identified, the ${}^{36}\mathrm{S}(d,{}^3\mathrm{He}){}^{35}\mathrm{P}$ reaction has been revisited in inverse kinematics with the HELical Orbit Spectrometer (HELIOS) at the Argonne Tandem Linac Accelerator System (ATLAS). While a candidate state has not been located, an upper limit for the transfer reaction cross section to populate such a configuration within a 2.5 to 3.6 MeV energy range provides a stringent constraint on the wave function compositions in both ${}^{36}\mathrm{S}$ and ${}^{35}\mathrm{P}$.

Background: Deep-inelastic scattering (DIS) on the polarized deuteron with detection of a proton in the nuclear breakup region (spectator tagging) represents a unique method for extracting the neutron spin structure functions and studying nuclear modifications. The tagged proton momentum controls the nuclear configuration during the DIS process and enables a differential analysis of nuclear effects. Such measurements could be performed with the future electron-ion collider (EIC) and forward proton detectors if deuteron beam polarization could be achieved.

Purpose: Develop a theoretical framework for polarized deuteron DIS with spectator tagging. Formulate practical procedures for neutron spin structure extraction.

Methods: A covariant spin density matrix formalism is used to describe general deuteron polarization in collider experiments (vector/tensor, pure/mixed). Light-front (LF) quantum mechanics is employed to factorize nuclear and nucleonic structure in the DIS process. A four-dimensional representation of LF spin structure is used to construct the polarized deuteron LF wave function and efficiently evaluate the spin sums. Free neutron structure is extracted using the impulse approximation and analyticity in the tagged proton momentum (pole extrapolation).

Results: General expressions of the polarized tagged DIS observables in collider experiments are presented. The polarized deuteron LF spectral function and nucleon momentum distributions are characterized in analytic and numerical form. Practical procedures for neutron spin structure extraction from the tagged deuteron spin asymmetries are proposed.

Conclusions: Spectator tagging provides new tools for precise neutron spin structure measurements. $D$-wave depolarization and nuclear binding effects can be eliminated through the tagged proton momentum dependence. The methods can be extended to tensor-polarized observables, spin-orbit effects, and diffractive processes.

The proton, antiproton, and mixed proton-antiproton factorial cumulants originating from the global conservation of baryon number are calculated analytically up to the sixth order. Our results can be directly tested in experiments.

Short-range correlations (SRCs) have been identified as being responsible for the high-momentum tail of the nucleon momentum distribution, $n\left(k\right)$. Hard, short-range interactions of nucleon pairs generate the high-momentum tail and imprint a universal character on $n\left(k\right)$ for all nuclei at large momentum. Triple coincidence experiments have shown a strong dominance of $np$ pairs, but these measurements involve large final-state interactions. This paper presents the results from Jefferson Lab experiment E08014 which measured inclusive electron scattering cross section from Ca isotopes. By comparing the inclusive cross section from ${}^{48}\mathrm{Ca}$ to ${}^{40}\mathrm{Ca}$ in a kinematic region dominated by SRCs we provide a new way to study the isospin structure of SRCs.

The yrast and nonyrast level structure of the odd-odd ${}^{78}\mathrm{As}$ nucleus has been investigated using the standard $\gamma$ ray spectroscopic techniques. The excited states of ${}^{78}\mathrm{As}$ were populated through ${}^{76}\mathrm{Ge}(\alpha ,pn)$ fusion evaporation reaction at the incident beam energies of 30, 35, and 40 MeV. The deexciting gamma rays were detected with the Indian National Gamma Array spectrometer composed of Clover and low-energy photon spectrometer detectors. In addition to the extension of the previously known yrast positive-parity band up to $E_x$ $\approx$ 2.7 MeV with $J=11\hslash$, an excited dipole band-like structure based on the $7^{(-)}$, 1243-keV state has also newly been established. Several weak transitions feeding the low-lying nonyrast states have newly been identified and placed in the level scheme. A highly irregular sequence of levels has been observed at the low-excitation regime suggesting the dominance of single-particle excitations. The experimental results have been compared with the predicted results from the large-scale shell-model calculations. The calculated results indicate an enhanced contribution from the intruder $\pi (1g_{9/2})$ orbital to the wave function of the positive-parity yrast excited states with $J\ge 7\hslash$. This enhanced contribution is supposed to provide subsequent mild collectivity for the concerned states. The nature of collectivity has been extracted from the total Routhian surface calculations. Evidences for the possible persistence of the stapler like mechanism prevailing in the positive- and negative-parity level sequences are presented.

We demonstrate the capability of coupled-cluster theory to compute the Coulomb sum rule for the ${}^4\mathrm{He}$ and ${}^{16}\mathrm{O}$ nuclei using interactions from chiral effective field theory. We perform several checks, including a few-body benchmark for ${}^4\mathrm{He}$. We provide an analysis of the center-of-mass contaminations, which we are able to safely remove. We then compare with other theoretical results and experimental data available in the literature, obtaining a fair agreement. This is a first and necessary step towards initiating a program for computing neutrino-nucleus interactions from first principles in coupled-cluster theory and supporting the experimental long-baseline neutrino program with a state-of-the-art theory that can reach medium-mass nuclei.

Excited states in ${}^{66}\mathrm{Zn}$ were investigated through the in-beam $\gamma$-ray spectroscopic techniques using the ${}^{52}\mathrm{Cr}({}^{18}\mathrm{O}, 2p2n$) fusion-evaporation reaction at a beam energy of 72.5 MeV. The $\gamma$-rays emitted by the de-exciting nuclei were recorded in coincidence mode using the 14 Compton suppressed Ge clover detectors of the Indian National Gamma Array. With 14 new transitions being identified, the level scheme of ${}^{66}\mathrm{Zn}$ has been extended up to the excitation energy $\approx 12.3\mathrm{MeV}$ and spin $\approx 17\hslash$. A rotational band, associated with the two quasineutrons from the $1g_{9/2}$ orbital, has been found to exhibit a band crossing with the ground-state band at a spin of $6\hslash$. The evolution of the collectivity and shape transition in this nucleus have been discussed in the framework of the total Routhian surface calculations and in comparison with the neighboring ${}^{68,70}\mathrm{Ge}$ nuclei.

Lifetimes of low-spin excited states in ${}^{98}\mathrm{Zr}$ were measured using the recoil-distance Doppler-shift technique and the Doppler-shift attenuation method. The nucleus of interest was populated in a ${}^{96}\mathrm{Zr}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{98}\mathrm{Zr}$ two-neutron transfer reaction at the Cologne FN Tandem accelerator. Lifetimes of six low-spin excited states, of which four are unknown, were measured. The deduced $B\left(E2\right)$ values were compared with Monte Carlo shell model and interacting boson model with configuration mixing calculations. Both approaches reproduce well most of the data but leave challenging questions regarding the structure of some low-lying states.

Clustering in ${}^{18}\mathrm{O}$ is of great interest to the nuclear physics community, due to theoretical predictions of $\mathrm{core}+\alpha$ and nuclear molecular structures. An experiment was performed in order to measure branching ratios for states in ${}^{18}\mathrm{O}$, determining the tendency towards clustering based on the value of ${\mathrm{\Gamma }}_{\alpha }/{\mathrm{\Gamma }}_{\text{tot}}$ for each state, and the reduced widths compared to the Wigner limit. An experimental method that enables the measurement of branching ratios for almost all available decay modes, including $\gamma$ decay, $\alpha$ decay, and $n$ decay, was employed. The method is also sensitive to the population of excited states in daughter nuclei, allowing for more accurate determination of the ${\alpha }_0$ branch. The measurements represent, for several states, either the first branching ratio measurement or the first determination of ${\mathrm{\Gamma }}_{\alpha }/{\mathrm{\Gamma }}_{\text{tot}}$. Based on these measurements, no evidence of consistent cluster structure is seen across any of the bands previously proposed, casting doubt on their existence. Despite this, some states displaying cluster structure are observed.

Background: Nucleon-knockout reactions on proton targets ($p,pN$) have experienced a renewed interest due to the availability of inverse-kinematics experiments with exotic nuclei. Various theoretical descriptions have been used to describe these reactions, such as the distorted-wave impulse approximation, the Faddeev-type formalism, and the transfer-to-the-continuum method.

Purpose: Our goal is to benchmark the observables computed with the Faddeev and transfer-to-the-continuum formalisms in the intermediate energy regime relevant for the experimental ($p,pn$) and ($p,2p$) studies.

Method: We analyze the ${}^{11}\mathrm{Be}(p,pn){}^{10}\mathrm{Be}$ reaction for different beam energies, binding energies, and orbital quantum numbers with both formalisms to assess their agreement for different observables.

Results: We obtain a good agreement in all cases considered, within $\approx 10\%$, when the input potentials are taken consistently and realistically.

Conclusions: The results of this work prove the consistency and accuracy of both methods, setting an indication on the degree of systematic uncertainties applicable when using them to extract spectroscopic information from ($p,pN$) reactions.

Quantum tunneling in many-body systems is the subject of many experimental and theoretical studies in fields ranging from cold atoms to nuclear physics. However, theoretical description of quantum tunneling with strongly interacting particles, such as nucleons in atomic nuclei, remains a major challenge in quantum physics. An initial-value approach to tunneling accounting for the degrees of freedom of each interacting particle is highly desirable. Inspired by existing methods to describe instantons with periodic solutions in imaginary time, we investigate the possibility to use an initial value approach to describe tunneling at the mean-field level. Real-time and imaginary-time Hartree dynamics are compared to the exact solution in the case of two particles in a two-well potential. Whereas real-time evolutions exhibit a spurious self-trapping effect preventing tunneling in strongly interacting systems, the imaginary-time-dependent mean-field method predicts tunneling rates in excellent agreement with the exact solution. Being an initial-value method, it could be more suitable than approaches requiring periodic solutions to describe realistic systems such as heavy-ion fusion.

Photoproduction cross sections are reported for the reaction $\gamma p\to p\eta$ using energy-tagged photons and the CLAS spectrometer at Jefferson Laboratory. The $\eta$ mesons are detected in their dominant charged decay mode, $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$, and results on differential cross sections are presented for incident photon energies between 1.2 and 4.7 GeV. These new $\eta$ photoproduction data are consistent with earlier CLAS results but extend the energy range beyond the nucleon resonance region into the Regge regime. The normalized angular distributions are also compared with the experimental results from several other experiments, and with predictions of $\eta$-MAID 2018 and the latest solution of the Bonn-Gatchina coupled-channel analysis. Differential cross sections $d\sigma /dt$ are presented for incident photon energies $E_{\gamma }>2.9\mathrm{GeV}$ ($W>2.5\mathrm{GeV}$), and compared with predictions which are based on Regge trajectories exchange in the $t$-channel (Regge models). The data confirm the expected dominance of $\rho$, $\omega$ vector-meson exchange in an analysis by the Joint Physics Analysis Center.