Experiments were performed at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron Facility to study the decays of neutron-deficient dubnium isotopes. These isotopes were produced in the ${}^{206}\mathrm{Pb}({}^{51}\mathrm{V}, xn){}^{255,256}\mathrm{Db}$ reaction, and excitation functions were measured. This article reports on the observed properties of the ${}^{256}\mathrm{Db}$ decay chain. The produced ${}^{256}\mathrm{Db}$ nuclei were separated from unreacted-beam material and reaction byproducts with the Berkeley Gas-filled Separator (BGS) before being implanted into a double-sided silicon strip detector at the BGS focal plane. Decay properties of ${}^{256}\mathrm{Db}$ and its daughters were then extracted from the analysis of correlations between implanted Db nuclei with $\alpha$ decay chains and spontaneous fission (SF) events. In total, 86 decay chains and 38 SF events were observed, giving increased statistics as compared to previous studies. Improved decay data are presented for ${}^{256}\mathrm{Db}$ and its daughter isotopes ${}^{252}\mathrm{Lr}, {}^{252}\mathrm{No}, {}^{248}\mathrm{Md}, {}^{248}\mathrm{Fm}, {}^{244}\mathrm{Es}$, and ${}^{244}\mathrm{Cf}$.

Angular distributions of the elastic and inelastic deuteron-nucleus scattering off ${}^{24}\mathrm{Mg},$ ${}^{28}\mathrm{Si},$ ${}^{58}\mathrm{Ni},$ ${}^{90}\mathrm{Zr},$ ${}^{116}\mathrm{Sn},$ and ${}^{208}\mathrm{Pb}$ have been measured at a beam energy of 98 MeV/nucleon, with the goal of constraining the deuteron optical potential in this kinematical regime and to extract the reduced transition probabilities for the ground-state transitions to low-lying excited states of these nuclei. Two potential models were used in the analysis of the measured $(d,d)$ and $(d,d^{\prime })$ data within the optical model and the distorted-wave Born approximation: the phenomenological optical model potential associated with the collective model of nuclear scattering, and the semimicroscopic double-folding model of the deuteron-nucleus potential based on a realistic density-dependent M3Y interaction. The deuteron optical potential and inelastic $(d,d^{\prime })$ scattering form factors were calculated using these two potential models, allowing for a direct comparison between the potential models as well as the validation of the deduced $E\lambda$ transition rates.

The negative parity structure in the ${}^{139}\mathrm{Pm}$ nucleus has been investigated through the ${}^{116}\mathrm{Cd}$ $({}^{31}\mathrm{P},$ $\alpha 4\mathrm{n})$ reaction at $E_{\mathrm{lab}}=148\mathrm{MeV}$ using the Indian National Gamma Array. The experimental $B{\left(E2\right)}_{\mathrm{out}}/B{\left(E2\right)}_{\mathrm{in}}$ and $B{\left(M1\right)}_{\mathrm{out}}/B{\left(E2\right)}_{\mathrm{in}}$ ratios along with the quasiparticle triaxial rotor model using the frozen alignment approximation calculations for the low-lying quadrupole bands QB1, QB2, QB3 and QB4 lead to the conclusion that the transverse wobbling structures for the first and second phonon may exist in ${}^{139}\mathrm{Pm}$. In addition, measured $B\left(M1\right)$ and $B\left(E2\right)$ rates for the dipole bands DB1 and DB2 agree with the shears mechanism with principal axis cranking model calculations. Thus, the existence of the magnetic rotational bands DB1 and DB2 after the first and second quasiparticle crossing support the origin of the quadrupole bands QB1, QB2, QB3, and QB4 from the wobbling excitation.

Within the ultrarelativistic quantum molecular dynamics (UrQMD) model, by reversely tracing nucleons emitted within different rapidity ($y_z$) and transverse momentum ($p_t$) windows in the final state, the time evolution of elliptic flow ($v_2$) of these nucleons produced in $\text{Au}+\text{Au}$ collisions with beam energies ($E_{\text{lab}}$) of 0.4, and 0.8 GeV/nucleon is studied. It is found that at $E_{\text{lab}}=0.4$ GeV/nucleon, the rapidity and transverse momentum of nucleons in the final state are correlated with the initial momentum. At $E_{\text{lab}}=0.8$ GeV/nucleon, the correlation becomes rather weak. In addition, by studying the medium density and the maximum density defined for each traced nucleon, it is found that the density interval at which the nuclear equation of state is probed by the elliptic flow is about 60–80 % of the maximum average density created in the central region of heavy-ion collision.

Background: The involvement of noncompound nuclear reactions in light and medium-heavy compound nuclei is not fully understood. In this regime, breakup fusion is regarded as the predominant reaction mode among all noncompound nuclear processes and has not been much explored explicitly.

Purpose: A systematic study of the compound nucleus fusion probability of various compound nuclei populated through different target-projectile systems is undertaken to investigate its dependence on various entrance channel parameters. The study provides better insight to determine the onset of noncompound nucleus fusion, due to which compound nucleus fusion probability reduces.

Method: In the present investigations, excitation functions of evaporation residues of 40 reactions leading to the formation of the compound nucleus in the mass region $\approx$ 64–195 have been taken into account from the literature. The compound nucleus fusion probability of these systems was calculated as the ratio of the compound nucleus fusion to the total fusion cross sections.

Results: Reduction in compound nucleus fusion probability was observed with an increase in parameters such as the projectile energy, the charge of the target, the total asymmetry, and the critical angular momentum of the different systems. Moreover, the $\alpha -Q$ value of the projectiles was found to affect and trigger the noncompound nuclear fusion processes more than other entrance channel parameters. It was also observed from the present analysis that the values of maximum angular momenta are slightly larger than the values of critical angular momenta as extracted from the measured cross sections for the studied systems.

Conclusions: The present study reveals the presence of noncompound nuclear fusion reactions in light- and medium-mass compound nuclei. This is mainly because of the loss in the flux of the compound nuclear fusion reaction and the subsequent gain in the flux of the noncompound nuclear fusion reaction. The observations further show that these processes are significantly influenced by the $\alpha -Q$ value of the projectiles. These results indicate that noncompound nuclear fusion processes occur in peripheral collisions.

The ${}^{25,26}\mathrm{Mg}(\alpha ,n){}^{28,29}\mathrm{Si}$ reactions have been shown to be influential to ${}^{26}\mathrm{Al}$ production in massive stars. The previously measured data sets for these reactions have discrepant results, and further study is warranted. The first measurements are reported of the total reaction cross sections of these reactions using direct recoil detection. The results are in good agreement with previous data sets based upon differential cross section studies. Astrophysical reaction rates based on the experimental data are reported and are within a factor of 1.5 of previous statistical model estimates.

In this paper, we employ the density dependent relativistic hadron (DDRH) field theoretical model in a Bayesian analysis to investigate the equation of state (EOS) of dense matter featuring antikaon condensation for $K^{-}$ and ${\overline{K}}^0$ inside neutron stars. The vector coupling parameters within the kaonic sector are determined through the isospin counting rule and quark model. Our study integrates various constraints, including chiral effective field theory ($\chi \mathrm{EFT}$) calculations, nuclear saturation properties, and astrophysical observations from pulsars PSR $\mathrm{J}0030+0451$ and PSR $\mathrm{J}0740+66$ and from the GW170817 event. We present posterior distributions of model parameters derived from these constraints, enabling us to explore the distributions of nuclear matter properties and neutron star (NS) characteristics such as radii, tidal deformabilities, central energy densities, and speed of sound. The antikaon potential at the 68(90)% confidence intervals is determined to be $-129.{36}_{-3.837(-5.696)}^{+12.53(+32.617)}\mathrm{MeV}$. This aligns with several studies providing estimates within the range of $-120$ to $-150\mathrm{MeV}$. We find that the maximum neutron star mass is constrained to around $2M_{\odot }$ due to the significant softening of the EOS caused by antikaon condensation. This softening results in a considerable decrease in the speed of sound. Although antikaon condensation for $K^{-}$ is not feasible inside canonical neutron stars, it becomes feasible for higher NS masses. The condensation of both $K^{-}$ and ${\overline{K}}^0$ is probably present in the interior of neutron stars with mass greater than $2M_{\odot }$. We also discuss the interconnections among input variables, isoscalar and isovector aspects of the EOS, and specific NS properties in the context of antikaon condensation.

In this work, we study the effect of strong magnetic fields on the equation of state (EoS) of warm, homogeneous, neutron star (NS) matter in beta equilibrium. NS matter is described within a relativistic mean field (RMF) approximation, including both models with nonlinear meson terms or with density-dependent nucleon-meson couplings. We first study the effect of magnetic fields and finite temperature on the EoS separately, finding that the effect of the latter to be significantly stronger than the one of the former. We then study the combined effect of magnetic fields and temperature on the internal composition. We show how both factors cause an increase in the proton fraction at low density and that, as long as the temperatures considered are not higher than 10 MeV, the effect of the magnetic field on the proton fraction is not small enough to be neglected.

Experiments conducted at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron Facility aimed to produce and study the decay of the previously unobserved isotope ${}^{255}\mathrm{Db}$. This isotope was produced in the ${}^{206}\mathrm{Pb}({}^{51}\mathrm{V}, 2n){}^{255}\mathrm{Db}$ reaction, separated from unreacted beam material and reaction by-products with the Berkeley Gas-filled Separator, and then implanted into a double-sided silicon-strip detector at the BGS focal plane. Decay properties of ${}^{255}\mathrm{Db}$ were determined from the analysis of evaporation residue (EVR) fission and EVR-$\alpha \text{−}\alpha$ correlations. The properties of this new isotope of dubnium differ dramatically from those of its neighboring Db isotopes. ${}^{255}\mathrm{Db}$ was found to decay primarily by spontaneous fission (SF) with a small $\alpha$-decay branch, where the average half-life of the observed decays was $t_{1/2}=2.6_{-0.3}^{+0.4}$ ms. Theoretical calculations were performed using the Wentzel-Kramers-Brillouin approximation, with parameters calculated within a self-consistent microscopic approach, to see if these unique properties could be reproduced. A SF half-life estimate is obtained that closely matches the measured value, while simultaneously pointing out the sensitivities that need to be further constrained in future work.

I study the spatial structure of the Borromean nucleus ${}^{19}\mathrm{B}$ based on a deformed-core plus multineutron model within the Hartree-Fock-Bogoliubov method. To consistently understand the experimental data of the matter radius and the core-dineutron distance, I suggest the deformed-core ($\beta \ge 0.6$) plus six-neutron ($6n$) structure. The fractions of the $s$- and $p$-wave components in the dineutron are both predicted to be about 20% at $\beta =0.6$. At larger deformation, the $s$-wave component remains at about 20%, while the $p$-wave component increases significantly, in contrast to the spherical-core plus $2n$ model calculations, where the $s$ and $d$ waves are most of the components.

Applications of new techniques in machine learning are speeding up progress in research in various fields. In this work, we construct and evaluate a deep neural network (DNN) to be used within a Bayesian statistical framework as a faster and more reliable alternative to the Gaussian process (GP) emulator of an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model simulator of heavy-ion reactions at intermediate beam energies. We found strong evidence of the DNN being able to emulate the IBUU simulator's prediction on the strengths of protons' directed and elliptical flow very efficiently even with small training datasets and with accuracy about ten times higher than the GP. Limitations of our present work and future improvements are also discussed.

We consider the possibility that low energy nuclear reactions (LENRs) arise due to the conversion of a proton to a neutron through weak interactions. The resulting neutron forms a short-lived virtual state, which then gets captured by another nucleus through photon emission. This whole process happens under the framework of second-order perturbation theory. We find that the rate of this process is negligibly small in most cases. However, in the presence of a resonance the rate can be substantial and observable. As an example, we consider the transition ${}^{58}\mathrm{Ni}$ to ${}^{59}\mathrm{Ni}$ of the nickel nucleus, which shows a relatively narrow resonance at 7 keV. The rate in this case is found to be approximately ${10}^{-20}$ per second, which is experimentally observable. We argue that the mechanism is applicable to a wide range of nuclei and also for other processes which may not involve a weak interaction transition.

This study investigates quark-gluon plasma in heavy-ion collisions through two avenues: high-$p_{\perp }$ frameworks and hydrodynamic modeling. Using the ${\mathrm{T}}_{\text{R}}\mathrm{ENTo}$ model, we find that the $p=0$ value aligns well with high-$p_{\perp }$ data, in agreement with Bayesian analysis of the low-$p_{\perp }$ regime. While adjusting $p$ values may improve a fit to a particular high-$p_{\perp }$ observable, it does not permit an earlier onset of transverse expansion.

We investigate the possibility and impacts of a first-order phase transition from hadronic matter to quark matter in neutron stars (NSs) using two specific models: the parity doublet model for the hadronic phase and the Nambu–Jona-Lasinio–type model for the quark phase. By combining these models, we construct hybrid equations of state that capture the transition between the two phases. We explore the parameter space of both models to identify the conditions under which a first-order phase transition can occur and study its effects on NS properties. We identify the suitable parameter space and constrain the onset density of the first-order phase transition.

Historically, studied in the context of heavy-ion collisions, the extent to which free nucleon-nucleon cross sections are modified in-medium remains undetermined by these data sets. Therefore, we investigate the impact of $NN$ in-medium modifications on neutrino-nucleus cross section predictions using the GiBUU transport model. We find that including an in-medium lowering of the $NN$ cross section and density dependence on $\mathrm{\Delta }$ excitation improves agreement with MicroBooNE neutrino-argon scattering data. This is observed for both proton and neutral pion spectra in charged-current muon neutrino and neutral-current single pion production data sets. The impact of collision broadening of the $\mathrm{\Delta }$ resonance is also investigated. The absence of $\mathrm{\Delta }$ broadening is slightly favored, but the larger uncertainties on the pion production data prevent definitive conclusions.

The reduced basis method is used to construct a “universal” basis of Dirac orbitals that may be applicable throughout the nuclear chart to calibrate covariant energy density functionals. Relative to the successful development of a reduced basis emulator for the nonrelativistic Schrödinger equation, the Dirac equation adds an extra layer of complexity due to the existence of negative energy states, which complicates building an efficient reduced basis. However, once this problem is mitigated, the resulting reduced basis is able to accurately and efficiently reproduce the high-fidelity model at a fraction of the computational cost. We are confident that the resulting reduced basis will serve as a foundational element in developing rapid and accurate emulators. In turn, these emulators will play a critical role in the Bayesian optimization of covariant energy density functionals.

Based on the beyond-mean-field Skyrme-Hartree-Fock model, we investigate the shape coexistence in Ne isotopes and the effect of $\mathrm{\Lambda }$ hyperon on the energy level structure in the nuclei. The up-to-date Skyrme-type $N\mathrm{\Lambda }$ interaction SLL4 and the $NN$ interaction SGII are employed. Low-lying energy spectra of ${}^{20,22,24,26,28,30,32,34}\mathrm{Ne}$, including the low-lying states with $J\le 6$, are predicted, discussed in detail, and found in good agreement with experimental results. The electric quadrupole transition rates are also examined. The coexistences of a ground state rotational band and a $\beta$ vibrational band are revealed in ${}^{20,22,24}\mathrm{Ne}$. Unlike the previously discovered shrinkage effect of ${\mathrm{\Lambda }}_s$ on the ground state nuclei, it is found that the ${\mathrm{\Lambda }}_s$ may alter the excitation mode of the second band by affecting the distribution of the collective wave function, thereby causing the $\beta$ vibrational band transitions to a vibrational band with equidistant energy levels.

The use of quantality is discussed in the case of nuclei and other many-body systems such as atomic electrons. This dimensionless quantity is known to indicate when a many-body system behaves like a crystal or a quantum liquid. Its role is further analyzed by showing its relation to the scattering length. The emergence of a fundamental length scale, the limit radius, is also shown. It corresponds to the hard-core of the nucleon-nucleon interaction in the case of nucleons, and to a value close to the Bohr radius in the case of atomic electrons. The occurrence of a cluster phase in nuclei is analyzed using the quantality through its relation to the localization parameter, allowing for the identification of both the number of nucleons and the density as control parameters for the occurrence of this phase. The relation of the quantality to the magnitude of the interaction also exhibits a third dimensionless parameter, monitoring the magnitude of the spin-orbit effect in finite systems, through the realization of the pseudospin symmetry. The impact of quantality on the spin-orbit effect is compared in various many-body systems. The role of quantality in the relative effect of the binding energy and the shell one is also analyzed in nuclei. Finally, additional dimensionless quantities are proposed from the generalization of the quantality. Nuclei are found to be exceptional systems because all their dimensionless quantities are close to the order of unity, at variance with other many-body systems.

Deuteron-induced reactions on ${}^6\mathrm{Li}$ are important for nuclear structure studies and nuclear applications. A new experimental effort was dedicated to improve incomplete partial cross sections and the angular distribution information for $d+{}^6\mathrm{Li}$ reactions and to address the inconsistencies between various $R$-matrix evaluations of the ${}^8\mathrm{Be}$ system. The new measurements were performed over a deuteron energy range of 1.8 to 10 MeV with an angular distribution coverage of ${20}^{\circ }$–${170}^{\circ }$ for outgoing particles. The experiment simultaneously measured neutrons, charged particles, and $\gamma$ rays from the various exit channels of the $d+{}^6\mathrm{Li}$ reaction. The cross sections for open reaction channels measured simultaneously are presented. In addition, results for the ${}^6\mathrm{Li}(d,n){}^7\mathrm{Be}$ total cross section using the activation method are also presented.