Background: In neutrino oscillation experiments, the hadrons created in neutrino-nucleus collisions are becoming important observables. The description of final-state interactions (FSI) of hadrons with nuclei in the large phase space probed in these experiments poses a great challenge. In the analysis of neutrino experiments, which operate under semi-inclusive conditions, cascade models are commonly used for this task. The description of FSI under exclusive conditions on the other hand can be treated successfully by using relativistic optical potentials (ROPs).

Purpose: We formulate conditions under which the ROP approach and cascade model can be directly compared. Through this comparison the treatment of FSI in cascade models is studied and benchmarked.

Method: We study single proton knockout with data from the T2K experiment's near-detector muon neutrino flux. We feed the neut cascade model with events distributed according to the cross section of a relativistic distorted-wave impulse approximation (RDWIA) calculation that uses the real part of an optical potential (rROP). We impose cuts on the missing energy of the resulting events to define a set of events which undergo only elastic FSI; these can be compared to RDWIA calculations with the full optical potential.

Results: The neut cascade and ROP give similar cross sections for proton kinetic energies $T_p>150\mathrm{MeV}$ for carbon, oxygen, and calcium nuclei. A necessary condition is that a realistic nuclear density is used to introduce events in the cascade. For $T_p<100\mathrm{MeV}$ the ROP and neut cross sections diverge strongly in shape, and differences in magnitude are larger than 50%. Data of transverse kinematic imbalance allow us to discriminate between different approaches to FSI, in particular the large $\delta {\alpha }_T$ region is sensitive to the presence of nonelastic FSI. Due to experimental errors and a large nonquasielastic contribution, the comparison to T2K data does not give an unambiguous view of FSI. We discuss electron scattering data and provide results for kinematics covered in the $e4\nu$ analysis. We argue that with a simple cut in missing energy FSI can be studied with minimal confounding factors.

Conclusions: The agreement of the ROP and neut cascade under T2K conditions lends confidence to these models as a tool in neutrino oscillation analyses for sufficiently large nucleon kinetic energies. Our results urge caution when applying a cascade model for small nucleon energies. The assessment of model assumptions relevant to this region is strongly encouraged. The approach presented in this paper provides novel constraints on cascade models from proton-nucleus scattering and can be easily applied to other neutrino event generators.

Starting from a quantum theory of dissipation for nuclear collective motion introduced by Kerman and Koonin [Phys. Scr. 10, 118 (1974)], the time-dependent generator coordinate method (TDGCM) is extended to allow for dissipation effects in the description of induced fission dynamics. The extension is based on a generalization of the GCM generating functions that includes excited states, and the resulting equation of motion in the collective coordinates and excitation energy. With the assumption of a narrow Hamiltonian kernel, an expansion in a power series in collective momenta leads to a Schrödinger-like equation that explicitly includes a dissipation term, proportional to the momentum of the statistical wave function. An illustrative calculation is performed for induced fission of ${}^{228}\mathrm{Th}$. The three-dimensional model space includes the axially symmetric quadrupole and octupole shape variables, and the nuclear temperature. When compared with data for photoinduced fission of ${}^{228}\mathrm{Th}$, the calculated fission yields demonstrate the important role of the additional term in the Hamiltonian that explicitly takes into account the dissipation of energy of collective motion into intrinsic degrees of freedom.

Heavy-ion collisions at ultrarelativistic energies provide extreme conditions of energy density and temperature to produce a deconfined state of quarks and gluons. Xenon (Xe), being a deformed nucleus, further gives access to the effect of initial geometry on final state particle production. This study focuses on the effect of nuclear deformation and hadron cascade-time on the particle production and elliptic flow using a multiphase transport (AMPT) model in $\mathrm{Xe}+\mathrm{Xe}$ collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. We explore the effect of hadronic cascade time on identified particle production through the study of $p_{\mathrm{T}}$-differential particle ratios. The effect of hadronic cascade time on the generation of elliptic flow is studied by varying the cascade time between 5 and $25\mathrm{fm}/c$. This study shows the final state interactions among particles generate additional anisotropic flow with increasing hadron cascade time, especially at very low and high $p_{\mathrm{T}}$.

The thermonuclear rate of the ${}^{29}\mathrm{Si}(p,\gamma ){}^{30}\mathrm{P}$ reaction impacts the ${}^{29}\mathrm{Si}$ abundance in classical novae. A reliable reaction rate is essential for testing the nova paternity of presolar stardust grains. At present, the fact that no classical nova grains have been unambiguously identified in primitive meteorites among thousands of grains studied is puzzling, considering that classical novae are expected to be prolific producers of dust grains. We investigated the ${}^{29}\mathrm{Si}+p$ reaction at center-of-mass energies of $200\text{–}420\mathrm{keV}$, and present improved values for resonance energies, level excitation energies, resonance strengths, and branching ratios. One new resonance was found at a center-of-mass energy of $303\mathrm{keV}$. For an expected resonance at $215\mathrm{keV}$, an experimental upper limit could be determined for the strength. We evaluated the level structure near the proton threshold, and present new reaction rates based on all the available experimental information. Our new reaction rates have much reduced uncertainties compared with previous results at temperatures of $T\ge 140$ MK, which are most important for classical nova nucleosynthesis. Future experiments to improve the reaction rates at lower temperatures are discussed.

A momentum-dependent formulation based on a stationary spin-0 and isospin-1 dibaryon field is proposed to improve convergence of chiral effective field theory in the ${}^1{S}_0$ channel of $NN$ scattering. Although the two-parameter leading-order interaction appears to be unnatural, it nevertheless has the necessary features of an effective field theory. A rapid order-by-order convergence is found in ${}^1{S}_0$. As an application beyond the two-body level, the triton binding energy is studied and compared to standard chiral effective field theory with partly perturbative pions. The consistency of the chiral Lagrangian for the new formulation is examined by working out the pionic radiative corrections, and consequences of nontrivial chiral-connection terms are discussed.

Background: Improved ${}^{95}\mathrm{Mo}$ neutron resonance parameters and reaction rates are important for nuclear astrophysics, testing nuclear models, and nuclear criticality safety. However, despite many previous neutron-capture and total cross-section measurements on this nuclide, there still is much room for improvement as well as several discrepancies. For example, there are very few firm resonance spin and parity assignments; average resonance parameters are available only for each parity, the currently recommended astrophysical reaction rate results in disagreements between stellar models and meteoric isotopic anomalies, and there are substantial disagreements in the neutron-capture cross section at low energies important for nuclear criticality safety.

Purpose: To obtain an improved set of neutron resonance parameters and astrophysical reaction rates for ${}^{95}\mathrm{Mo}$.

Method: High-resolution neutron-capture and transmission data were measured at the Oak Ridge Electron Linear Accelerator (ORELA) using highly isotopically enriched ${}^{95}\mathrm{Mo}$ samples. The neutron-capture apparatus, data reduction, and analysis were improved so that information contained in the $\gamma$-ray cascade following neutron capture were used to assign resonance $J^{\pi }$ values. Following this, simultaneous analysis of the new neutron-capture and transmission data was used to obtain resonance energies, gamma widths, and neutron widths and their uncertainties to a maximum energy of 10 keV. Accurate neutron-capture cross sections also were obtained for the unresolved resonance region to a maximum energy of 500 keV and, together with the new resonance parameters, used to calculate the astrophysical reaction rates in the temperature range from 5 to 30 keV.

Results: A vastly improved set of ${}^{95}\mathrm{Mo}$ neutron resonance parameters and an astrophysical reaction rate accurate to about 3% were obtained. Firm $J^{\pi }$ assignments were determined for 261 of the 314 observed resonances. This is a very large improvement over the previously published 32 firm $J^{\pi }$ assignments for 108 resonances. Also, the number of resonances having both firm $J^{\pi }$ assignments and ${\mathrm{\Gamma }}_{\gamma }$ values was increased by almost a factor of 24—from 11 to 261. Neutron- and total-radiation-width distributions and average resonance spacings, average total radiation widths, and neutron strength functions were obtained for the six different $s$- and $p$-wave possibilities. Parameters for the lowest $s$-wave resonance, which is most important for criticality benchmarks, were obtained with high accuracy.

Conclusions: Simple modification of the neutron-capture apparatus and expansion and improvement of data analysis techniques led to a large increase in firm $J^{\pi }$ assignments for ${}^{95}\mathrm{Mo}$ neutron resonances. The resulting astrophysical reaction rate is 20%–30% larger than the currently recommended rate at $s$-process temperatures, which should lead to better agreement between stellar models and meteoric isotopic anomalies. The neutron-capture cross section at low energies is substantially larger than recommended in the latest evaluation, which is problematical for criticality benchmarks. The average resonance spacing as a function of spin and parity is significantly different from current models. The total-radiation-width distributions are significantly broader than predicted by theory and show significant departures from the expected Gaussian shapes.

Excited states in odd-odd ${}^{70}\mathrm{Ga}$ were studied using the ${}^{62}\mathrm{Ni}({}^{14}\mathrm{C},\alpha pn)$ fusion-evaporation reaction performed at the John D. Fox Superconducting Accelerator Facility at Florida State University with a beam energy of 50 MeV. The depopulating $\gamma$ decays were measured in coincidence using a Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. An investigation of these coincidences resulted in the addition of 16 new transitions in the ${}^{70}\mathrm{Ga}$ level scheme, including some which belong to the onset of a new positive-parity band structure likely based on the $\pi g_{9/2}\otimes \nu g_{9/2}$ configuration. Spins and parities were assigned based on directional correlation of oriented nuclei ratios and linear polarization measurements. The excitation energies predicted by shell-model calculations using the JUN45 effective interaction compare favorably with the experimental ones for the positive-parity states, but are generally about 400–500 keV too low for the negative-parity states. Total Routhian surface calculations for the lowest positive-parity configuration with signature $\alpha =0$ predict significant triaxiality $(\gamma \approx -{20}^{\circ })$ with competing noncollective excitations developing at a spin $(J=8)$ that corresponds to the onset of the positive-parity band observed experimentally. The calculations for the lowest negative-parity states with $\alpha =0$ yielded surfaces that were qualitatively similar.

A well-known structure with concentrated Gamow-Teller (GT) transitions is the Gamow-Teller resonance, which has been observed at higher-energy regions (usually $>6$ MeV) of nuclear excitation. It has been found that the GT strength can also concentrate in the lowest $J^{\pi }=1^{+}$ GT state named the “low-energy super-GT (LeSGT) state” when the initial even-even nucleus has the structure of “LS-closed-shell core nucleus $+$ 2 neutrons (or 2 protons)” and the final nucleus “LS-closed-shell core nucleus $+$ 1 proton and 1 neutron.” Such concentrations are realized with the core nuclei ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$, corresponding to the shell closures of $s$, $p$, and $sd$ shells, respectively. It is natural to speculate that the LeSGT state may also be observed in the $A=82$ systems if the $N=Z=40$ shell gap is significant and ${}^{80}\mathrm{Zr}$ represents a good core nucleus corresponding to the $pf$ shell closure. Possible conditions that allow the formation of the LeSGT state in the ${}^{82}\mathrm{Zr}\to {}^{82}\mathrm{Nb}$ charge-exchange reaction (or ${}^{82}\mathrm{Mo}\to {}^{82}\mathrm{Nb}\beta$ decay) are discussed by evaluating the results of projected shell model calculations, which are based on deformed model space. Our calculations show that with increasing deformation, the LeSGT feature found in the spherical limit (zero deformation) evolves gradually into a broad distribution in the higher-energy region. This lets us conclude that no LeSGT state is expected in ${}^{82}\mathrm{Nb}$ because the shape of the ${}^{80}\mathrm{Zr}$ core nucleus is ellipsoidal.

The relativistic Brueckner-Hartree-Fock equations are solved self-consistently for symmetric nuclear matter in the full Dirac space within the continuous choice for the single-particle potential. Inspired from the nucleon-nucleon scattering in the free space, the energy denominator of the scattering equation in the nuclear medium is rewritten and a complex Thompson equation for the effective interaction $G$ matrix is derived. By decomposing the matrix elements of the single-particle potential operator in the full Dirac space, both the real and the imaginary parts of the single-particle potential are determined uniquely. The single-particle energy and Dirac mass behave continuously through the Fermi surface as expected. By comparing the equation of state obtained within the continuous choice with that obtained within the gap choice and in-between choice, the convergence of the hole-line expansion is discussed.

The MUon Scattering Experiment, MUSE, at the Paul Scherrer Institute, Switzerland, investigates the proton charge radius puzzle, lepton universality, and two-photon exchange, via simultaneous measurements of elastic muon-proton and electron-proton scattering. The experiment uses the PiM1 secondary beam channel, which was designed for high precision pion scattering measurements. We review the properties of the beam line established for pions. We discuss the production processes that generate the electron and muon beams, and the simulations of these processes. Simulations of the $\pi /\mu /e$ beams through the channel using TURTLE and G4beamline are compared. The G4beamline simulation is then compared to several experimental measurements of the channel, including the momentum dispersion at the intermediate focal plane and target, the shape of the beam spot at the target, and timing measurements that allow the beam momenta to be determined. We conclude that the PiM1 channel can be used for high precision $\pi$, $\mu$, and $e$ scattering.

The weak $r$ process in neutrino-driven winds following a core-collapse supernova is thought to contribute to the cosmic abundances of the first $r$-process peak elements between Se and Ag. Sensitivity studies have found that the early nucleosynthesis in the weak $r$ process is primarily driven by $(\alpha ,xn)$ reactions due to the high temperatures, and that current nuclear physics uncertainties in the $(\alpha ,xn)$ rates result in significant uncertainties of the calculated abundances. The weak $r$-process path proceeds several nuclei away from stability where $(\alpha ,xn)$ reaction cross sections have not yet been measured. In this paper we report the ${}^{100}\mathrm{Mo}(\alpha ,xn)$ cross section (between 8.9 and 13.2 MeV in the center of mass, corresponding to 3.5–6.8 GK) in inverse kinematics using the Multi-Sampling Ionization Chamber (MUSIC) detector at the Argonne Tandem Linac Accelerator System (ATLAS) facility. With this first measurement of the ${}^{100}\mathrm{Mo}(\alpha ,xn)$ cross section, we have demonstrated the ability of MUSIC to measure $(\alpha ,xn)$ cross sections for $A$ up to 100, therefore paving the way for further measurements with radioactive beams at ATLAS or the Facility for Rare Isotope Beams.

Using the microscopic-macroscopic approach based on the modified two-center shell model, the ground-state shell corrections are analyzed as a function of spin-orbit strength for even-$Z$ superheavy nuclei in the $\alpha$-decay chains containing ${}^{295–300,302,304}120$ nuclei. The influence of the spin-orbit strength on the positions of shell closures and the description of the low-lying one-quasiparticle spectra for ${}^{251}\mathrm{Cf}, {}^{243}\mathrm{Cm}, {}^{243}\mathrm{Bk}$, and ${}^{251}\mathrm{Es}$ nuclei are studied in detail. The importance of studying the nuclear structure of actinides for predicting the next double magic nucleus beyond ${}^{208}\mathrm{Pb}$ is demonstrated.

Background: A multitude of broad interfering resonances characterize the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ cross section at low energies. The complexity of the reaction mechanism, as well as conflicting experimental measurements, have so far prevented a reliable prediction of the cross section over the energy ranges pertinent for a boron-proton fusion reactor environment.

Purpose: To improve the evaluated cross section of the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ reaction, this study targets the proton energy region from 0.8 to 2.0 MeV, where kinematic overlap of the scattered protons and reaction $\alpha$ particles have made past measurements very challenging.

Method: New detailed studies of the reaction have been performed at the Edwards Accelerator Laboratory at Ohio University and the Nuclear Science Laboratory at the University of Notre Dame using time-of-flight and degrader foil techniques, respectively.

Results: Proton and $\alpha$-particle signals were clearly resolved using both techniques, and 16 point differential cross sections were measured over an angular range of ${\theta }_{\text{lab}}={45}^{\circ }$ and $157.5^{\circ }$. A comprehensive $R$-matrix analysis of the experimental data, including data from previous low-energy studies of the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}, {}^{10}\mathrm{B}(p,p){}^{10}\mathrm{B}$, and ${}^{10}\mathrm{B}(p,\gamma ){}^{11}\mathrm{C}$ reactions, was achieved over the region of measurement. Using a representative set of previous data, the fit was extended to very low energies.

Conclusions: On the basis of this data and $R$-matrix analysis, a more reliable and consistent description of the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ cross section has been established. The uncertainty over the energy range of this study has been reduced from $\approx 20\%$ to $\approx 10\%$, and the level structure over this region has been clarified considerably.

In the context of the potential laser-induced enhancement to the rates of ${\mathrm{DHe}}^3$ and DT fusion, we discuss the frequently-used Wentzel-Kramers-Brillouin (WKB) method and the imaginary-time method (ITM). For static external electric fields, we find that these methods predict significant enhancement to the fusion cross section for electric-field strengths $>{10}^{14}$ V/m, especially at low values ($\approx$ keV) for the enter-of-mass (CoM) energy. When considering dynamic electric fields, this enhancement can be amplified by considering increased photon frequencies. However, we also provide a review of the region of laser-parameter phase space where these semiclassical methods are applicable. We conclude that this allowable region decreases for higher photon frequencies in conjunction with lower values for the electric-field strength, motivating the need for future experiments to test the predictions of these methods and their ranges of validity.

The high-energy $\gamma$ rays have been measured in proton and $\alpha$-induced reactions on medium mass target nuclei ${}^{115}\mathrm{In}$ and ${}^{112}\mathrm{Sn}$, respectively. Theoretical analyses of the spectra have been performed within the Hauser-Feshbach statistical model and the Akkermans-Gruppelaar exciton model formalisms. It is observed that the proton-induced reaction has significant contribution from the direct-semidirect capture in the region $E_{\gamma } \approx \mathrm{10–20}$ MeV. The ${}^4\mathrm{He}$-ion-induced reaction could be described reasonably well by the results of the statistical model calculations. A reduced level density parameter, as compared to that used for the proton-induced reaction, was required to explain the high-energy $\gamma$-ray spectrum in the ${}^4\mathrm{He}$-ion-induced reaction.

We report a measurement of the half-life of the ${}^{136}\mathrm{Xe}$ two-neutrino double-$\beta$ decay performed with a novel direct-background-subtraction technique. The analysis relies on the data collected with the NEXT-White detector operated with ${}^{136}\mathrm{Xe}$-enriched and ${}^{136}\mathrm{Xe}$-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of $2.{34}_{-0.46}^{+0.80}{\text{(stat)}}_{-0.17}^{+0.30}\text{(sys)}\times {10}^{21}\text{yr}$ is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double-$\beta$-decay searches.

Dispersion corrections to elastic electron scattering from a ${}^{12}\mathrm{C}$ nucleus are calculated within the second-order Born approximation. Three strong transient nuclear excitations are considered, at 4.439 MeV $\left(2^{+}\right)$, 17.7 MeV $\left(1^{-}\right),$ and 23.5 MeV $\left(1^{-}\right)$. The Friar-Rosen-type Coulomb term is supplemented with the transverse part of the photon propagator. It is found that the dispersive cross-section changes in the first diffraction minimum reach nearly 10%, rising more slowly with collision energy beyond 400 MeV. Magnetic scattering can be strong for the individual excited states and lowers the dispersion effect considerably at energies below 400 MeV. However, it contributes at most 10% at the higher energies investigated.

Structures in the ${}^{106}\mathrm{Pd}$ nucleus have been studied in the $\mathrm{EC}/{\beta }^{+}$ decay of ${}^{106}\mathrm{Ag}$ at the INFN Legnaro National Laboratories using the Spes Low-energy Internal Conversion Electron Spectrometer (SLICES). The K-conversion coefficients and the electric monopole transition strengths, between low-lying $2^{+}$ and $0^{+}$ states, have been studied. These experimental data combined with the results from conversion electron measurement on ${}^{104}\mathrm{Pd}$ previously performed by the Florence spectroscopy group were compared with the theoretical values calculated in the framework of the interacting proton-neutron boson model. Good agreement between experimental and theoretical values is found when interpreting the $0_3^{+}$ level as an intruder state.

Heavy quark dynamics in an anisotropic QCD medium have been analyzed within the Fokker-Planck approach. Heavy quark drag force and the momentum diffusion tensor have been decomposed by employing a general tensor basis for an anisotropic medium. Depending upon the relative orientation of the direction of the momentum anisotropy of the medium and heavy quark motion, two drag and four diffusion coefficients have been estimated in the anisotropic QCD medium. The relative significance of different components of drag and momentum diffusion coefficients has been explored. The dependence of the angle between the anisotropic vector and heavy quark motion to the drag and diffusion coefficients has also been studied. Furthermore, the energy loss of heavy quarks due to the elastic collisional process in an anisotropic medium has been studied. It is seen that the anisotropic contributions to heavy quark transport coefficients and its collisional energy loss have a strong dependence on the direction and strength of momentum anisotropy in the QCD medium.