Recent advances in both theoretical and computational methods have enabled large-scale, precision calculations of the properties of atomic nuclei. With the growing complexity of modern nuclear theory, however, also comes the need for novel methods to perform systematic studies and quantify the uncertainties of models when confronted with experimental data. This study presents an application of such an approach, the reduced basis method, to substantially lower computational costs by constructing a significantly smaller Hamiltonian subspace informed by previous solutions. Our method shows comparable efficiency and accuracy to other dimensionality reduction techniques on an artificial three-body bound system while providing a richer representation of physical information in its projection and training subspace. This methodological advancement can be applied in other contexts and has the potential to greatly improve our ability to systematically explore theoretical models and thus enhance our understanding of the fundamental properties of nuclear systems.

We propose an algorithm for simulating stochastic relativistic fluid dynamics based on Metropolis updates. Each step of the algorithm begins with an update based on ideal hydrodynamics. This is followed by proposing random (spatial) momentum transfers between fluid cells, keeping the total energy fixed. These proposals are then accepted or rejected using the change in entropy as a statistical weight. The algorithm reproduces relativistic viscous hydrodynamics in the “density frame,” which is a formulation of viscous hydrodynamics we review and clarify here. This formulation is first order in time and requires no auxiliary dynamical fields such as ${\mathrm{\Pi }}^{\mu \nu }$. The only parameters are the shear and bulk viscosities and the equation of state. By adopting the $3+1$ split of general relativity, we extend the Metropolis algorithm to general space-time coordinates, such as Bjorken coordinates, which are commonly used to simulate heavy-ion collisions.

We conduct a numerical study of relativistic viscous fluid dynamics in the density frame for one-dimensional fluid flows. The density frame is a formulation of relativistic viscous hydrodynamics that is first order in time, requires no auxiliary fields, and has no nonhydrodynamic modes. We compare our results to QCD kinetic theory simulations and find excellent agreement within the regime of applicability of hydrodynamics. Additionally, the density frame results remain well behaved and robust near the boundary of applicability. We also compare our findings to the second-order-in-time hydrodynamic theory developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK) and a well-known Müller-Israel-Stewart-type hydrodynamics code, music, which is commonly used to simulate heavy-ion collisions.

Right-handed weak currents (RHCs) in the left-right symmetric model for neutrinoless double beta decays (DBDs) of both the $0^{+}\to 0^{+}$ and $0^{+}\to 2^{+}$ transitions are discussed from both theoretical and experimental viewpoints. $\langle \lambda \rangle$ and $\langle \eta \rangle$ terms are related by $\langle \lambda \rangle /\langle \eta \rangle \approx tan\beta$, which is constrained in the regions of 1–60 for SUSY grand unified theories (GUTs) and of 1–165 for non-SUSY GUTs. The enhancement mechanisms of the $\langle \eta \rangle$ term over the $\langle \lambda \rangle$ term in the $0^{+}$ transition is shown, and the $\mathrm{\Delta }$ isobar contribution to the nuclear matrix element (NME) for the transition to the $2^{+}$ state is found to be of the order of $20\%$ of the NME with the quenched weak coupling. The new and interesting RHC regions of $\langle \lambda \rangle \approx 5\times {10}^{-8}$ and $\langle \eta \rangle \approx 1.5\times {10}^{-10}$ are shown to be exclusively explored by measuring both the $\beta \beta$ and $\gamma$ rays associated with the ground and excited DBDs by means of the ton-scale DBD detectors for the inverted hierarchy $\nu$ masses. The actual RHCs to be studied depend on the RHC NMEs.

The potential presence of wobbling motion in octupole deformed nuclei is investigated within the framework of the octupole core-quasiparticle coupling (OCQPC) model for the $\pi (2g_{9/2},1j_{15/2})$ configuration. Key experimentally measurable quantities, including energy spectra, electromagnetic transition probabilities, $g$-factors, and spectroscopic quadrupole moments, are calculated. A detailed analysis is conducted on the probability distributions of the core and particle angular momenta, along with the associated angular momentum components. Distinct signatures of wobbling motion emerge in both positive and negative parity doublet bands. For instance, the interband $B{\left(E2\right)}_{\text{out}}$ displays collective enhancement, whereas the interband $B{\left(M1\right)}_{\text{out}}$ shows relative suppression. As the total spin $I$ increases, the rotational mode transitions from principal axis rotation about the short axis to rotation about the medium axis, shifting the wobbling mode from transverse to longitudinal. The positive and negative parity wobbling doublet bands are connected by electric dipole transitions, with their probabilities increasing with spin, suggesting enhanced octupole correlations.

Measurements of fission $\gamma$ rays emitted as a function of time since fission from the ${}^{235}\mathrm{U}(n,f)$ and ${}^{252}\mathrm{Cf}\left(\mathrm{sf}\right)$ reactions were carried out with the detectors array DANCE. A fission event was identified by registering a prompt fission neutron with the NEUANCE array placed inside DANCE and surrounding the target. All $\gamma$ rays, fission or background, following the fission events were recorded. Some of the background events were removed during the data reduction by applying multiplicity and total $\gamma$-ray energy cuts. A method for estimating the accidental $\gamma$-ray background was applied to clean the data from the remaining background. Energy spectra of the fission $\gamma$ rays were collected as a function of the time since fission occurred. The experimental results are compared with predictions of the CGMF code folded with GEANT4 simulations of the DANCE with NEUANCE detector response.

The relationship between medium modifications of nucleon electromagnetic form factors and nucleon structure functions is examined using a model [Kim and Miller, Phys. Rev. C 106, 055202 (2022)] motivated by light-front holographic QCD. The previous work emphasized studying bound-nucleon structure functions, the current work is concerned with a detailed look at bound-nucleon form factors. We find that the sizes of the medium modifications to nucleon form factors and structure functions are similar, both are around 5–15%. In order to make this comparison, an analytic-form derivation of the linear nuclear EMC effect is presented. In our model, the modifications are closely connected to the influence of short-ranged correlations due to the presence of large virtuality in our results. Contrary to a recent calculation [Xing, Wang, and Thomas, Phys. Lett. B 846, 138195 (2023)], our model suggests that short-ranged correlations do not cause large form factor modifications.

The role of radiative corrections in low-energy nuclear physics is beginning to receive more scrutiny. We examine the impact of these corrections for the deuteron charge form factor and the radiative capture process $np\to d\gamma$ through the velocity renormalization group. In both cases, we find percent-level shifts in the relevant observables after evolving the subtraction velocity to the typical velocity of nucleons in the bound state. This suggests that electromagnetic corrections constitute a non-negligible source of uncertainty in existing few-body calculations.

The particle-number-conserving (PNC) method in the framework of the deformed shell model is employed to study the properties of the newly discovered short-lived neutron-deficient nucleus ${}^{224}\mathrm{Np}$ and its $\alpha$ decay. The calculated energy of the $\alpha$ particle lies within 300 keV of the experimental data. This is the first application of the PNC method to the region of neutron-deficient nuclei. This work provides the first attempt to combine the microscopic PNC theory with empirical formulas to study the nuclear $\alpha$ decay. The configurations of ground states are assigned as $\pi 5/2^{-}\left[523\right]\otimes \nu 5/2^{+}\left[633\right]$ for ${}^{224}\mathrm{Np}$, $\pi 1/2^{-}\left[530\right]\otimes \nu 3/2^{+}\left[642\right]$ for ${}^{220}\mathrm{Pa}$, $\pi 3/2^{+}\left[651\right]\otimes \nu 1/2^{-}\left[501\right]$ for ${}^{216}\mathrm{Ac}$, and $\pi 7/2^{-}\left[514\right]\otimes \nu 3/2^{-}\left[501\right]$ for ${}^{212}\mathrm{Fr}$. The proton subshell at $Z=92$ disappeared in ${}^{224}\mathrm{Np}$. Low-lying excited states are predicted for nuclei along the $\alpha$-decay chain by the PNC method. Based on the PNC predicted $\alpha$-decay energy and the assigned configurations, the $\alpha$-decay half-lives are calculated by the empirical formulas, in which the angular momentum taken away by the $\alpha$ particle is taken into account. The angular momentum has an important effect on the $\alpha$-decay half-life. The errors of the empirical formula calculation are of two orders of magnitude with the experimental data.

An accurate understanding of charged particle induced reactions is important for astrophysics and nuclear applications. Evaluations of light nuclei reaction cross sections are often performed using resonance matrix analysis and play a fundamental role in nuclear data libraries such as ENDF. Prompted by recent experimental measurements, an improved $R$-matrix analysis for the ${}^8\mathrm{Be}$ system is presented. It is compared to existing evaluations and discrepancies are discussed and often resolved. These comparisons are facilitated by a Bayesian uncertainty analysis that produces uncertainties for the $R$-matrix parameters and experimental cross sections. The $R$-matrix parameters reported in this work pave the way for an update to the current ENDF evaluation. The impact of this work on key reactions, such as ${}^6\mathrm{Li}(d,n){}^7\mathrm{Be}$, ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$, ${}^7\mathrm{Li}(p,\gamma ){}^8\mathrm{Be}$, and ${}^7\mathrm{Be}(n,p){}^7\mathrm{Li}$, which are used in nuclear applications and astrophysics, is discussed.

We propose a new method to study the evolution of the neutron periphery between different isotopes by considering antiproton-nucleus interactions close to the production threshold of $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ and ${\mathrm{\Sigma }}^{-}\overline{\mathrm{\Lambda }}$ pairs. At low energies, $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ pairs are produced in $\overline{p}+p$ collisions, while ${\mathrm{\Sigma }}^{-}\overline{\mathrm{\Lambda }}$ pairs can only be produced in $\overline{p}+n$ interactions. Within a simple geometrical picture we show that the double ratio for the production of ${\mathrm{\Sigma }}^{-}\overline{\mathrm{\Lambda }}$ and $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ pairs for two different isotopes are related to the variation of the neutron skin thickness between the two nuclei. Performing high statistics calculations with the Gießen Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model for several isotope pairs covering a wide range of elements, we verify a strong correlation between the double ratio from the full transport simulations and the schematic model. This correlation enables us to quantify the potential of the proposed method for precise studies of neutron skin variations in isotope chains.

The nuclei belonging to the actinide region are radioactive and may proceed to the exit channel via various disintegration modes. One of the interesting candidates is the ${}^{252}\mathrm{Cf}$ nucleus, which may disintegrate via binary, ternary, and or quaternary channels. The present work explores these decay modes using a quantum mechanical fragmentation theory (QMFT)-based approach. First of all, the most common decay mode, i.e., binary decay, is explored using the fragmentation structure. The most probable decaying fragments are identified in reference to the minima of the fragmentation potential. The competing analysis of these fragments triggered that the α decay is the most prominent disintegration mode among its competing channels. Interestingly, the α particle is also experimentally detected in ternary ($A_1^{\prime },\alpha ,A_2^{\prime }$) and quaternary ($A_1^{″},\alpha ,\alpha ,A_2^{″}$) processes. Hence, it will be of interest to do a competing analysis of these decay modes ($\alpha +$one/two/three fragments) using the collective clusterization approach. The particles heavier than α are detected in different decay modes of ${}^{252}\mathrm{Cf}$ nucleus, which motivated us to study the heavy particle-accompanied fission. The emergence of heavy fragment modes are worked out in view of the fragmentation structure, and the most probable heavy fragments are identified in view of three- ($A_1^{\prime }\ge A_2^{\prime }\ge A_3^{\prime }$) and four-body ($A_1^{″}\ge A_2^{″}\ge A_3^{″}\ge A_4^{″}$) emission mode. Interestingly, few cases are identified where ternary and quaternary fission seems equally probable. After the fragmentation analysis, the barrier characteristics of probable combinations are compared, respectively. The results are compared with the available experimental data and few predictions are made for future validations. In addition to this, the relative yield of ternary and quaternary fission is analyzed by taking different surface separation ($s$).

The Solenoidal Tracker at RHIC (STAR) experiment at the Relativistic Heavy Ion Collider reports new measurements of jet quenching based on the semi-inclusive distribution of charged-particle jets recoiling from direct photon $\left({\gamma }_{\mathrm{dir}}\right)$ and neutral pion $\left({\pi }^0\right)$ triggers in $\mathit{pp}$ and central $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ for triggers in the range $9<E_T^{\mathrm{trig}}<20\mathrm{GeV}$. The datasets have integrated luminosities of $3.9{\mathrm{nb}}^{-1}$ for $\mathrm{Au}+\mathrm{Au}$ and $23{\mathrm{pb}}^{-1}$ for $\mathit{pp}$ collisions. Jets are reconstructed using the anti-$k_T$ algorithm with resolution parameters $R=0.2$ and 0.5. The large uncorrelated jet background in central $\mathrm{Au}+\mathrm{Au}$ collisions is corrected using a mixed-event approach, which enables precise charged-particle jet measurements at low transverse momentum $p_{T,\mathrm{jet}}^{\mathrm{ch}}$ and large $R$. Recoil-jet distributions are reported in the range $p_{T,\mathrm{jet}}^{\mathrm{ch}}<25 \mathrm{GeV}/c$. Comparison of the distributions measured in $\mathit{pp}$ and $\mathrm{Au}+\mathrm{Au}$ collisions reveals strong medium-induced jet yield suppression for $R=0.2$ with markedly less suppression for $R=0.5$. Comparison is also made to theoretical models incorporating jet quenching. These data provide new insight into the mechanisms underlying jet quenching and the angular dependence of medium-induced jet-energy transport and provide new constraints on modeling such effects.

High-resolution $\gamma$-ray spectroscopy and fast-timing methods were employed to study the excited structure of ${}^{128}\mathrm{Sn}$, populated via the $\beta$-decay chain of ${}^{128}\mathrm{Cd}\to {}^{128}\mathrm{In}\to {}^{128}\mathrm{Sn}$. The experiment was performed by online mass separation at the ISOLDE facility at CERN, profiting from intense and pure Cd beams obtained by a temperature-controlled quartz transfer line combined with resonant laser ionization. An extended ${}^{128}\mathrm{Sn}$ level scheme populated in the ${\beta }^{-}$ decay of the low-spin ${}^{128}\mathrm{In}$ isomer was constructed, adding a total of 81 new $\gamma$-ray transitions and 30 new levels. Lifetimes of excited states were measured using time-delayed $\beta \gamma \left(t\right)$ and $\gamma \gamma \left(t\right)$ coincidences. The lifetime of the $\left(4^{+}\right)$ state was measured for the first time, making it possible to deduce the $B(E2;$ $4^{+}\to 2^{+})$ transition strength. The previously measured $\left(5^{-}\right)$ state was reassessed with improved statistics. Additionally, an upper limit for the lifetime of the state at 2378 keV was established. The derived reduced transition probabilities support a tentative spin-parity assignment of $\left(4^{-}\right)$ for this level. The experimental level scheme and transition probabilities are compared with available shell-model calculations.

A systematic study of the isoscalar giant monopole resonance (ISGMR) in a wide range of nuclei from various isotopic chains is performed within the microscopic self-consistent Skyrme Hartree-Fock plus Bardeen-Cooper-Schrieffer ($\mathrm{HF}+\mathrm{BCS}$) method and coherent density fluctuation model (CDFM). The calculations for the nuclear incompressibility are based on the Brueckner and Barcelona-Catania-Paris-Madrid (BCPM) energy density functionals for nuclear matter using the capability of the CDFM to make a transition to the corresponding incompressibility in finite nuclei. The results obtained by applying different definitions of the ISGMR energy, as well as the two energy-density functionals, are analyzed and compared with the available experimental data. The peculiarities of the proton and neutron density distributions and their corresponding linear size characteristics are considered. In general, a connection with the measured neutron skin thicknesses is proposed as a possible way to obtain realistic estimations of the energy of ISGMR.

In this work, we propose an effective finite-range Gogny-type interaction that can be directly used in the quantum-molecular-dynamics-like models. Two methods for determining the parameters of the effective interaction are discussed. The first method establishes an approach to connect the conventional Gogny interaction used in nuclear structure field to that in heavy-ion collisions field. The second method allows for the description of the symmetry energy varying from supersoft to stiff, as well as the momentum-dependent symmetry potential, exhibiting behaviors ranging from monotonic to nonmonotonic variations. This effective interaction opens up opportunities for a deeper understanding of finite-range interactions and nonmonotonic momentum-dependent symmetry potentials in future studies.

We investigate nuclear transparency induced by pion electroproduction on nuclei, $A(e,e^{\prime }{\pi }^{+})$, with our interest in the role of the two-step process in the Glauber multiple scattering theory. Based on the framework in which the quantum diffusion model is incorporated into the Glauber theory, the experimental data in the range of photon virtuality $0.5<Q^2<10{\mathrm{GeV}}^2/c^2$ are analyzed, including the recent JLab data at the 6 GeV electron beam together with the proposal for the 12 GeV upgrade. Application of the quantum diffusion model during the formation length of the quark/antiquark $\left(q\overline{q}\right)$ structure of a pion reproduces the increase in the nuclear transparency up to high $Q^2$, showing evidence of color transparency. In contrast, through the coherent length of the ${\gamma }^{*}$ fluctuation into ${\rho }^0$, the two-step process with the $\rho N$ scattering cross section chosen to be ${\sigma }_{\rho N}={\sigma }_{\pi N}$ contributes to a reduction of the nuclear transparency in the whole range of $Q^2$. Combined with the one-step process (direct photon coupling) usually adopted in the original formulation of the Glauber theory, this reaction mechanism provides another source of the $Q^2$ dependence of the transparency at low virtualities through the shadowing in the initial state interaction. By the further absorption due to the shadowing, a better agreement is obtained with the pion transparency measured in the $A(e,e^{\prime }{\pi }^{+})$ reaction for ${}^{12}\mathrm{C}$, ${}^{27}\mathrm{Al}$, ${}^{63}\mathrm{Cu}$, and ${}^{197}\mathrm{Au}$ nuclei. A discussion of the $Q^2$ dependence of the parameter $\alpha$ for the transparency $T_A=A^{\alpha -1}$ is given.