In relativistic heavy-ion collisions, jet quenching in quark-gluon plasma (QGP) has been extensively studied, revealing important insights into the properties of the color deconfined nuclear matter. Over the past decade, there has been a surge of interest in the exploration of QGP droplets in small collision systems, such as $p+p$ or $p+A$ collisions, driven by the observation of collective flow phenomena. However, the absence of jet quenching, a key QGP signature, in these systems poses a puzzle. Understanding how jet quenching evolves with system size is crucial for uncovering the underlying physics. In this study, we employ the linear Boltzmann transport (LBT) model to investigate jet modification in ${}^{96}\mathrm{Ru}+{}^{96}\mathrm{Ru}, {}^{96}\mathrm{Zr}+{}^{96}\mathrm{Zr}$, and ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200$ GeV. Our findings highlight the system size sensitivity exhibited by jet nuclear modification factor ($R_{AA}$) and jet shape ($\rho$), contrasting to the relatively weak responses of jet mass ($M$), girth ($g$) and momentum dispersion ($p_{\mathrm{T}}D$) to system size variations. These results offer invaluable insights into the system size dependence of the QGP properties and await experimental validation at the Relativistic Heavy-Ion Collider.

The E895 and STAR experiments demonstrate that the slopes of directed flow with respect to rapidity ($d{v}_1{/dy|}_{y=0}$) of mesons are negative in the low transverse momentum ($p_T$) region, $p_T<0.8\mathrm{GeV}/c$, in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=3.0–3.9\mathrm{GeV}$. Using the transport model JAM, we investigate the directed flow of ${\pi }^{\pm }, K^{\pm }$, and $K^0$ as functions of rapidity, $p_T$, and collision energy in $\mathrm{Au}+\mathrm{Au}$ collisions at the same energies as those in the E895 and STAR experiments. We find that the JAM model can qualitatively reproduce the antiflow of $K_S^0$ observed in the E895 experiment. The $v_1$ slopes of pions and kaons are analyzed as functions of the $p_T$ window, revealing a strong $p_T$ dependence of the $v_1$ slopes. Negative $v_1$ slopes are observed in the low $p_T$ region, $p_T<0.8\mathrm{GeV}/c$, while positive slopes are shown in the higher $p_T$ region. We find that the shadowing effect from spectators is crucial in generating the antiflow of mesons at low $p_T$ in the high baryon density region.

We propose a simplified approach to incorporate the long-range proton-proton ($pp$) Coulomb force in three-nucleon (3N) scattering calculations, based on the exact formulation presented by Witała, Skibiński, Golak, and Glöckle [Eur. Phys. J. A 41, 369 (2009) and Eur. Phys. J. A 41, 385 (2009)]. It permits us to get elastic proton-deuteron ($pd$) scattering and breakup observables relatively simply by performing standard Faddeev calculations as known for the neutron-deuteron ($nd$) system. The basic ingredient in that approach is a three-dimensional screened $pp$ Coulomb $t$-matrix obtained by numerical solution of the three-dimensional Lippmann-Schwinger (LS) equation. Based on this $t$-matrix, pure Coulomb transition terms contributing to elastic scattering and breakup are calculated without any need for partial-wave decomposition. For elastic scattering such a term removes the Rutherford amplitude for point deuteron proton-deuteron ($pd$) scattering. For breakup it provides contributions which are important in some regions of the breakup phase space. We demonstrate numerically that the $pd$ elastic observables can be determined directly from the resulting 3N amplitudes without any renormalization, simply by increasing the screening radius in order to reach the existing screening limit. However, for $pd$ breakup the renormalization of the contributing on-shell amplitudes is required. We apply our approach in a wide energy range of the incoming proton for $pd$ elastic scattering as well as for the $pd$ breakup reaction.

Collective nuclear excitations, like giant resonances, are sensitive to nuclear deformation, as evidenced by alterations in their excitation energies and transition strength distributions. A common theoretical framework to study these collective modes, the random-phase approximation (RPA), has to deal with large dimensions spanned by all possible particle-hole configurations satisfying certain symmetries. It is the aim of this work to establish a new theoretical framework to study the impact of deformation on spin-isospin excitations, that is able to provide fast and reliable solutions of the RPA equations. The nuclear ground state is determined with the axially deformed relativistic Hartree-Bogoliubov (RHB) model based on relativistic point-coupling energy density functionals (EDFs). To study the excitations in the charge-exchange channel, an axially deformed proton-neutron relativistic quasiparticle RPA (pnRQRPA) is developed in the linear response approach. After benchmarking the axially deformed pnRQRPA in the spherical limit, a study of spin-isospin excitations including Fermi, Gamow-Teller (GT), and spin-dipole (SD) is performed for selected $pf$-shell nuclei. For GT transitions, it is demonstrated that deformation leads to a considerable fragmentation of the strength function. A mechanism inducing the fragmentation is studied by decomposing the total strength to different projections of total angular momentum $K$ and constraining the nuclear shape to either spherical, prolate, or oblate. A similar fragmentation is also observed for SD transitions, although somewhat moderated by the complex structure of these transitions, while, as expected, the Fermi strength is almost shape independent. The axially deformed pnRQRPA introduced in this work open perspectives for the future studies of deformation effects on astrophysically relevant weak interaction processes, in particular beta decay and electron capture.

The $E2$ transition matrix elements of isobaric multiplets are expected to follow a linear trend as a function of isospin projection. However, measurements of the $2^{+}\to 0^{+}$ transitions in the $A=38$ triplet of Ca, K, and Ar show a deviation from this trend with an enhanced transition strength in ${}^{38}\mathrm{Ca}$ with respect to its mirror ${}^{38}\mathrm{Ar}$. We have studied analogue $11/2^{-}\to 7/2^{-} E2$ transitions in ${}^{39}\mathrm{Ca}$ and its mirror partner ${}^{39}\mathrm{K}$ to determine if this enhancement persists in neighboring Ca isotopes. Recoil-distance lifetime measurements of ${}^{39}\mathrm{Ca}$ and ${}^{39}\mathrm{K}$ were performed utilizing a ${}^{42}\mathrm{Sc}$ secondary beam, the TRIPLEX plunger, the GRETINA array, and the S800 spectrograph. Our data provide a lifetime measurement of the ($11/2^{-}$) state in ${}^{39}\mathrm{Ca}$ as well as an improved lifetime result for the ($9/2^{-}$) state, while the ${}^{39}\mathrm{K}$ data are used to validate the present analysis. A comparison of the present data to shell-model calculations suggests an enhanced transition strength in ${}^{39}\mathrm{Ca}$, pointing to both proton and neutron contributions to core excitations across the $Z=N=20$ shell gaps in close proximity to ${}^{40}\mathrm{Ca}$.

The structure of the negative parity bands, based on the $\nu h_{11/2}$ orbital, in ${}^{129}\mathrm{Ba}$ is revisited to search for the wobbling mode in this nucleus. Existing angular distribution/correlation and linear polarization results are indicative of a large $E2$ admixture in the 365 keV interconnecting $\mathrm{\Delta }I=1$ $\gamma$ transition between yrast bands. This provides an indication of the existence of a wobbling mode in this nucleus. Theoretical calculations performed in this work using the quasiparticle plus triaxial rotor model have effectively replicated the available experimental results.

Collective flow has been found to be similar between small colliding systems ($p+p$ and $\mathrm{p}+\mathrm{A}$ collisions) and large colliding systems (peripheral $\mathrm{A}+\mathrm{A}$ collisions) at the CERN Large Hadron Collider. In order to study the differences of collective flow between small and large colliding systems, we employ a point-cloud network to identify $p+$ Pb collisions and peripheral Pb $+$ Pb collisions at $\sqrt{s_{\text{NN}}}=5.02$ TeV generated from a multiphase transport model. After removing the discrepancies in the pseudorapidity distribution and the $p_{\mathrm{T}}$ spectra, we capture the discrepancy in collective flow. Although the verification accuracy of our PCN is limited due to similar event-by-event distributions of elliptic and triangular flow, we demonstrate that collective flow between $p+$ Pb collisions and peripheral Pb $+$ Pb collisions becomes more distinct with increasing final hadron multiplicity and parton scattering cross section. This study not only highlights the potential of PCN techniques in advancing the understanding of collective flow in varying colliding systems, but more importantly lays the groundwork for the future PCN-related research.

Nuclear quantum many-body methods rely on integral transform techniques to infer properties of electroweak response functions from ground-state expectation values. Retrieving the energy dependence of these responses is highly nontrivial, especially for quantum Monte Carlo methods, as it requires inverting the Laplace transform, a notoriously ill-posed problem. In this work, we propose an artificial neural network architecture suitable for accurate response function reconstruction with precise estimation of the uncertainty of the inversion. We demonstrate the capabilities of this new architecture benchmarking it against maximum entropy and previously developed neural network methods designed for a similar task, paying particular attention to its robustness against increasing noise in the input Euclidean responses.

The $\beta$-decay properties of nuclei near the second nuclear “island of inversion” around neutron rich nuclei with neutron number 40 are important tests of nuclear structure models and interactions. In particular, the $\beta$-delayed neutron emission branch ($P_{\mathrm{n}}$), is useful for investigating $\beta$-strength and neutron-$\gamma$ competition above the neutron separation energies of the daughter nuclei. We report new constraints for $P_{\mathrm{n}}$ values for three nuclei in the region: ${}^{62}\mathrm{Cr}$ ($P_{\mathrm{n}}<1\%$), ${}^{64}\mathrm{Mn}$ ($P_{\mathrm{n}}=1.5\left(6\right)\%$), and ${}^{65}\mathrm{Fe}$ ($P_{\mathrm{n}}<1\%$), measured with the Neutron Emission Ratio Observer (NERO) neutron long counter system and the Beta Counting Station (BCS) at the National Superconducting Cyclotron Laboratory (NSCL). Our results resolve the large discrepancy between previous direct and indirect measurements for ${}^{64}\mathrm{Mn}$ and confirm the predictions of global theoretical models when a statistical treatment of the $\gamma$ and neutron decays of the daughter states is included. We also obtain improved half-lives for ${}^{62}\mathrm{Cr}$ [206(5) ms] and the short-lived isomer in the ${}^{62}\mathrm{Fe}$ daughter [112(7) ms] from $\beta$-delayed $\gamma$ emission data obtained in the same experiment with the Summing NaI (SuN) total absorption spectrometer. Finally, we use $\gamma$ emission data to obtain a new upper limit for the ${}^{62}\mathrm{Cr}\beta$-decay population of the long-lived isomeric state in ${}^{62}\mathrm{Mn}$.

Single-energy partial-wave analysis has often been applied as a way to fit data with minimal model dependence. However, remaining unconstrained, partial waves at neighboring energies will vary discontinuously because the overall amplitude phase cannot be determined through single-channel measurements. This problem can be mitigated through the use of a constraining penalty function based on an associated energy-dependent fit. However, the weight given to this constraint results in a biased fit to the data. In this paper, for the first time, we explore a constraining function which does not influence the fit to data. The constraint comes from the overall phase found in multichannel fits which, in the present study, are the Bonn-Gatchina and Jülich-Bonn multichannel analyses. The data are well reproduced and weighting of the penalty function does not influence the result. The method is applied to $K\mathrm{\Lambda }$ photoproduction data and all observables can be maximally well reproduced. While the employed multichannel analyses display very different multipole amplitudes, we show that the major difference between two sets of multipoles can be related to the different overall phases.

We study complete fusion (CF) reactions in collisions of ${}^6\mathrm{Li}$ projectiles with ${}^{28}\mathrm{Si}, {}^{64}\mathrm{Ni}$, and ${}^{159}\mathrm{Tb}$ targets, from sub-barrier energies up to energies well above the Coulomb barrier. For this purpose, we use a recently developed theoretical method, based on continuum discretized coupled channel wave functions, which successfully predicted CF data for heavier systems. To perform the numerical calculations, we developed a computer code where the continuum discretized wave functions are evaluated by the pseudostates method. We investigate the sensitivity of the results to the largest energy used in the continuum discretization, including closed channels. We find that very good convergence is reached by including continuum states with energies up to 15 MeV. We show that the theoretical CF cross sections of the present study reproduce the available data for the ${}^{28}\mathrm{Si}, {}^{64}\mathrm{Ni}$, and ${}^{159}\mathrm{Tb}$ targets fairly well. A detailed discussion of the static and dynamical effects of the low breakup threshold of the projectile on the CF cross section is presented, considering collisions with targets in different mass regions.

The most recent data on differential cross sections and photon beam asymmetries $\mathrm{\Sigma }$ from the LEPS2/BGOegg Collaboration for the $\gamma p\to f_0\left(980\right)p$ reaction are analyzed within a tree-level effective Lagrangian approach. The $t$-channel $\rho$ and $\omega$ exchanges, the $u$- and $s$-channel $N$ exchanges, the interaction current, and the possible $s$-channel $N^{*}$ exchanges are taken into account in constructing the reaction amplitudes to reproduce the data. The results show that the contributions from either the $N\left(2040\right)3/2^{+}$ or the $N\left(2100\right)1/2^{+}$ resonance exchange in the $s$ channel are necessarily required to describe the LEPS2/BGOegg data and they dominate the differential cross sections of $\gamma p\to f_0\left(980\right)p$. Further analysis shows that the contributions from the $t$-channel $\rho$ and $\omega$ exchanges and the interaction current are rather small to both differential cross sections and photo beam asymmetries, and the contributions from $u$-channel $N$ exchange are considerable in the case of including $N\left(2040\right)3/2^{+}$ in the model while negligible in the case of including $N\left(2100\right)1/2^{+}$ in the model. Predictions of target asymmetries $T$ for $\gamma p\to f_0\left(980\right)p$ are given, which can be examined by future experiments.

The ${}^{15}\mathrm{N}$($\alpha ,\gamma$)${}^{19}\mathrm{F}$ reaction produces ${}^{19}\mathrm{F}$ in asymptotic giant branch (AGB) stars, where the low energy tails of two resonances at $E_{\mathrm{c}.\mathrm{m}.}=1323\pm 2$ and $1487\pm 1.7\mathrm{keV}$ are estimated to contribute about 30% of the total reaction rate in these environments. However, recent measurements have shown discrepancies in the energies, the strengths, and the corresponding alpha widths of these two resonances, resulting in an increase in the systematic uncertainty of the extrapolated cross section to helium burning energies. With this motivation, we have undertaken new measurements of the ${}^{15}\mathrm{N}$($\alpha ,\gamma$)${}^{19}\mathrm{F}$ at the University of Notre Dame Nuclear Science Laboratory. The setup consisted of an alpha particle beam impinged on a solid $\mathrm{Ti}{}^{15}\mathrm{N}$ target with gamma-ray spectroscopy accomplished using a high purity germanium detector. Using the Doppler corrected gamma-ray energies, we confirmed the lower resonance energy to be $1321.6\pm 0.6\mathrm{keV}$ and found a value for the higher one of $1479.4\pm 0.6\mathrm{keV}$ that is more consistent with those found from previous elastic scattering studies. We found that the resonance strengths for both were consistent with most values found in the literature, but a larger alpha width has been recommended for the $E_{\mathrm{c}.\mathrm{m}.}=1487\mathrm{keV}$ resonance. The larger alpha width suggests a reaction rate increase of about $15\%$ at temperatures $T<0.1$ GK relevant to low mass AGB stars. The impact of the increased reaction rate requires further investigations.

The Gamow-Teller and Fermi matrix elements, $\langle \mathbf{GT}\rangle$ and $\langle \mathbf{F}\rangle$, respectively, for tritium $\beta$ decay are calculated to next-to-leading order (NLO) in pionless effective field theory in the absence of Coulomb interactions and isospin violation giving the leading order predictions ${\langle \mathbf{GT}\rangle }_0=0.9807$ and ${\langle \mathbf{F}\rangle }_0=1$. Using an experimentally determined value for the tritium $\beta$ decay GT matrix element, the two-body axial current low energy constant is fixed at NLO yielding $L_{1,A}=6.01\pm 2.08{\mathrm{fm}}^3$ at the renormalization scale of the physical pion mass, which agrees with predictions based on naive dimensional analysis. The impact of $L_{1,A}$ on proton-proton fusion is also discussed. Finally, the consequences of Wigner-SU(4) spin-isospin symmetry are considered for the Gamow-Teller matrix element.

The large-scale shell-model calculations have been performed for the neutron-rich nuclei in the south region of ${}^{208}\mathrm{Pb}$ in the nuclear chart. The $\beta$-decay properties, such as the $logft$, average shape factor values, half-lives, and partial decay rates are calculated for these neutron-rich nuclei using recent effective interaction for the ${}^{208}\mathrm{Pb}$ region. These calculations have been performed without truncation in a particular model space for nuclei $N\le 126$; additionally, particle-hole excitations are included in the case of core-breaking nuclei $(Z\le 82,N>126)$. An extensive comparison with the experimental data has been made, and spin parities of several states have been proposed.

We analyze the ${}^{12}\mathrm{C}({}^7\mathrm{Li},t){}^{16}\mathrm{O}$ transfer reaction in a semimicroscopic approach. We use fully antisymmetric $\alpha +{}^{12}\mathrm{C}$ wave functions defined in the resonating group method (RGM) to study the ${}^{16}\mathrm{O}$ spectroscopy and overlap integrals. We include several $\alpha +{}^{12}\mathrm{C}(0^{+},1^{+},2^{+},3^{+},4^{+})$ configurations. In the semimicroscopic calculations, we use the overlap integrals provided by the RGM formalism. The ${}^7\mathrm{Li}+{}^{12}\mathrm{C}$ scattering wave functions are defined in the continuum-discretized coupled channel (CDCC) model to include ${}^7\mathrm{Li}$ breakup effects. The CDCC approach is tested by analyzing elastic scattering data, which are satisfactorily described at small angles. Our semimicroscopic results are in fair agreement with the experimental ${}^{12}\mathrm{C}({}^7\mathrm{Li},t){}^{16}\mathrm{O}$ data. We also determine the mirror ${}^{12}\mathrm{C}({}^7\mathrm{Be},{}^3\mathrm{He}){}^{16}\mathrm{O}$ cross section, which is experimentally known. The transfer cross sections are obtained without any parameter fitting since the spectroscopic factors are an output of the RGM, and are not fitted to the data.

Calculations for the burn fraction in a laser-created plasma are presented, taking fuel depletion into account. The enhancement from a strong-field laser is analyzed and calculated in the Floquet-Volkoff framework, which was verified to provide an adequate theoretical prediction for laser-enhanced fusion cross sections in a previous work [Phys. Rev. C 109, 044605 (2024)]. Three different fuels were considered for the fusion process, namely deuterium-tritium (DT) fusion, deuterium-helium fusion, and proton-boron fusion. Their laser-enhanced burn fractions are compared in idealistic and realistic settings, where both thermal and nonthermal distributions are considered. It is found that DT fusion gains the least relative enhancement to the burn fraction in all scenarios considered, and that the remaining fuels do not gain an absolute enhancement large enough to be appreciable in comparison with the former.

The present work on low-energy reaction dynamics recognizes the importance of precompound emission as a paramount deexcitation process for emitting energetic particles, even at energies as low as $\approx 4–5$ MeV/nucleon, where the compound nucleus process has been identified as the sole contributor. This recognition is achieved by performing a comprehensive analysis of cross-section data for a large number of ($\alpha ,n$) reactions within the framework of the theoretical model-based codes cascade, pace4, and talys at varying energies above the Coulomb barrier. The analysis of the data provides a precise estimation of the precompound contribution with respect to its compound nucleus counterpart. Consistency in the rising trends of the precompound curves with the excitation energy and the atomic mass number of target nuclei indicates their origins from a common density domain within the excited nuclei. This commonality establishes a significant interconnection between nuclear structure and reaction dynamics for the participating surface nucleons in precompound process, except those that are emitted from the closed-shell nucleus in the $\alpha +{}_{37}{}^{85}\mathrm{Rb}\Rightarrow {}_{39}{}^{89}\mathrm{Y}(N=50)$ reaction. The present investigation explores additional understanding of the target deformation in determining the total precompound contribution.