We investigate the possibilities of producing neutron-rich nuclides in projectile fission of heavy beams in the energy range of 20 MeV/nucleon expected from low-energy facilities. We report our efforts to theoretically describe the reaction mechanism of projectile fission following a multinucleon transfer collision at this energy range. Our calculations are mainly based on a two-step approach: The dynamical stage of the collision is described with either the phenomenological deep-inelastic transfer model (DIT) or with the microscopic constrained molecular dynamics model (CoMD). The de-excitation or fission of the hot heavy projectile fragments is performed with the statistical multifragmentation model (SMM). We compared our model calculations with our previous experimental projectile-fission data of ${}^{238}\mathrm{U}$ (20 MeV/nucleon) + ${}^{208}\mathrm{Pb}$ and ${}^{197}\mathrm{Au}$ (20 MeV/nucleon) + ${}^{197}\mathrm{Au}$ and found an overall reasonable agreement. Our study suggests that projectile fission following peripheral heavy-ion collisions at this energy range offers an effective route to access very neutron-rich rare isotopes toward and beyond the astrophysical r-process path.

Relativistic generalization of hydrodynamic theory has attracted much attention from a theoretical point of view. However, it has many important practical applications in high energy as well as astrophysical contexts. Despite various attempts to formulate relativistic hydrodynamics, no definitive consensus has been achieved. In this work, we propose to test the predictions of four types of first-order hydrodynamic theories for nonperfect fluids in the light of numerically exact molecular dynamics simulations of a fully relativistic particle system in the low density regime. In this regard, we study the propagation of density, velocity, and heat fluctuations in a wide range of temperatures using extensive simulations and compare them to the corresponding analytic expressions we obtain for each of the proposed theories. As expected, in the low temperature classical regime all theories give the same results, consistent with the numerics. In the high temperature extremely relativistic regime, not all considered theories are distinguishable from one another. However, in the intermediate regime, a meaningful distinction exists in the predictions of various theories considered here. We find that the predictions of the recent formulation due to Tsumura, Kunihiro, and Ohnishi are more consistent with our numerical results than the traditional theories: the Meixner, modified Eckart, and modified Marle-Stewart theories.

We present a class of analytic solutions of nonrelativistic fireball hydrodynamics for a fairly general class of equation of state. The presented solution describes the expansion of a triaxial ellipsoid that rotates around one of its principal axes. We calculate the hadronic final state observables such as single-particle spectra, directed, elliptic, and third flows, as well as two-particle Bose-Einstein (also named HBT) correlations and corresponding radius parameters, utilizing simple analytic formulas. The final tilt angle of the fireball, an important observable quantity, is shown to be not independent of its exact definition: one gets different tilt angles from the geometrical anisotropies, from the single-particle spectra, and from HBT measurements. Taken together, the tilt angle in the momentum space and in the relative momentum or HBT variable may be sufficient for the determination of the magnitude of the rotation of the fireball. We argue that observing this rotation and its dependence on collision energy could characterize the softest point of the equation of state. Thus determining the rotation may be a powerful tool for the experimental search for the critical point in the phase diagram of strongly interacting matter.

In this article we extend previous work on efficiency corrections for cumulant measurements [Bzdak and Koch, Phys. Rev. C 86, 044904 (2012); Phys. Rev. C 91, 027901 (2015)]. We will discuss the limitations of the methods presented in these papers. Specifically we will consider multiplicity dependent efficiencies as well as nonbinomial efficiency distributions. We will discuss the most simple and straightforward methods to implement those corrections.

Energy-dependent and single-energy fits to the existing nucleon-nucleon database have been updated to incorporate recent measurements. The fits cover a region from threshold to 3 GeV, in the laboratory kinetic energy, for proton-proton scattering, with an upper limit of 1.3 GeV for neutron-proton scattering. Experiments carried out at the COSY-WASA and COSY-ANKE facilities have had a significant impact on the partial-wave solutions. Results are discussed in terms of both partial-wave and direct reconstruction amplitudes.

The ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ and ${}^{23}\mathrm{Na}(\alpha ,n){}^{26}\mathrm{Al}$ reactions are important for our understanding of the ${}^{26}\mathrm{Al}$ abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysically important reactions using an active target system. The reactions were investigated in inverse kinematics using ${}^4\mathrm{He}$ as the active target gas in the detector. We measured the excitation functions in the energy range of about 2 to 6 MeV in the center of mass. We have found that the cross sections of the ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ and the ${}^{23}\mathrm{Na}(\alpha ,n){}^{26}\mathrm{Al}$ reactions are in good agreement with previous experiments and with statistical-model calculations. The astrophysical reaction rate of the ${}^{23}\mathrm{Na}(\alpha ,n){}^{26}\mathrm{Al}$ reaction has been reevaluated and it was found to be larger than the recommended rate.

We present a measurement of the inclusive production of $\mathrm{{\rm Y}}$ mesons in U+U collisions at $\sqrt{s_{NN}}=193$ GeV at midrapidity $\left(\left|y\right|<1\right)$. Previous studies in central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV show a suppression of $\mathrm{{\rm Y}}\left(\text{1S+2S+3S}\right)$ production relative to expectations from the $\mathrm{{\rm Y}}$ yield in p+p collisions scaled by the number of binary nucleon-nucleon collisions $\left(N_{\mathrm{coll}}\right)$, with an indication that the $\mathrm{{\rm Y}}\left(\text{1S}\right)$ state is also suppressed. The present measurement extends the number of participant nucleons in the collision ($N_{\mathrm{part}}$) by 20% compared to Au+Au collisions, and allows us to study a system with higher energy density. We observe a suppression in both the $\mathrm{{\rm Y}}\left(1\mathrm{S}+2\mathrm{S}+3\mathrm{S}\right)$ and $\mathrm{{\rm Y}}\left(1\mathrm{S}\right)$ yields in central U+U data, which consolidates and extends the previously observed suppression trend in Au+Au collisions.

Background: The rate of the ${}^{18}\mathrm{F}(p,\gamma ){}^{19}\mathrm{Ne}$ reaction affects the final abundance of the radioisotope ${}^{18}\mathrm{F}$ ejected from novae. This nucleus is important as its abundance is thought to significantly influence the first-stage 511-keV and continuum $\gamma$-ray emission in the aftermath of novae. No successful measurement of this reaction existed prior to this work, and the rate used in stellar models had been calculated based on incomplete information from contributing resonances.

Purpose: Of the two resonances thought to provide a significant contribution to the astrophysical reaction rate, located at $E_{\mathrm{c}.\mathrm{m}.}=330$ and 665 keV, the former has a radiative width estimated from the assumed analog state in the mirror nucleus, ${}^{19}\mathrm{F}$, while the latter resonance does not have an analog state assignment, resulting in an arbitrary radiative width being assumed. As such, a direct measurement was needed to establish what role this resonance plays in the destruction of ${}^{18}\mathrm{F}$ at nova temperatures. This paper extends and takes the place of a previous Letter which reported the strength of the $E_{\mathrm{c}.\mathrm{m}.}=665$ keV resonance.

Method: The DRAGON recoil separator was used to directly measure the strength of the important 665-keV resonance in this reaction, in inverse kinematics, by observing ${}^{19}\mathrm{Ne}$ reaction products. A radioactive ${}^{18}\mathrm{F}$ beam was provided by the ISAC facility at TRIUMF. $R$-matrix calculations were subsequently used to evaluate the significance of the results at astrophysical energies.

Results: We report the direct measurement of the ${}^{18}\mathrm{F}(p,\gamma ){}^{19}\mathrm{Ne}$ reaction with the reevaluation of several detector efficiencies and the use of an updated ${}^{19}\mathrm{Ne}$ level scheme in the reaction rate analysis. The strength of the 665-keV resonance ($E_x=7.076$ MeV) is found to be an order of magnitude weaker than currently assumed in nova models. An improved analysis of the previously reported data is presented here, resulting in a slightly different value for the resonance strength. These small changes, however, do not alter the primary conclusions.

Conclusions: Reaction rate calculations definitively show that the 665-keV resonance plays no significant role in the destruction of ${}^{18}\mathrm{F}$ at nova temperatures.

A parametrization of the nucleon-nucleon elastic scattering amplitude is needed for future experiments with nucleon and nuclear beams in the beam momentum range of 2–50 $\mathrm{GeV}/c/\text{nucleon}$. There are many parametrizations of the amplitude at $P_{\mathrm{lab}}>$ 25–50 $\mathrm{GeV}/c$, and at $P_{\mathrm{lab}}\le 5$ $\mathrm{GeV}/c$. Our paper is aimed at covering the range between 5–50 $\mathrm{GeV}/c$. The amplitude is used in Glauber calculations of various cross sections and Monte Carlo simulations of nucleon-nucleon scatterings. Usually, the differential nucleon-nucleon elastic scattering cross sections are described by an exponential expression. Corresponding experimental data on $pp$ interactions at $\left|t\right|>$ 0.005 $(\mathrm{GeV}/c){}^2$ and $\left|t\right|\le 0.125$ $(\mathrm{GeV}/c){}^2$ have been fit. We propose formulas to approximate the beam momentum dependence of these parameters in the momentum range considered. The same was done for $np$ interactions at $\left|t\right|\le 0.5$ ($\mathrm{GeV}/c$)${}^2$. Expressions for the momentum dependence of the total and elastic cross sections, and the ratio of real to imaginary parts of the amplitude at zero momentum transfer are also given for $pp$ and $np$ collisions. These results are sufficient for a first approximation of the Glauber calculations. For more exact calculations we fit the data at $\left|t\right|>0.005$ $(\mathrm{GeV}/c){}^2$ without restrictions on the maximum value of $\left|t\right|$ using an expression based on two coherent exponentials. The parameters of the fits are found for the beam momentum range 2–50 $\mathrm{GeV}/c$.

New levels and $\gamma$-ray transitions were identified in ${}^{150,152}\mathrm{Sm}$ utilizing the $(p,t)$ reaction and particle-$\gamma$ coincidence data. A large, peak-like structure observed between 2.3–3.0 MeV in excitation energy in the triton energy spectra was also investigated. The orbital angular-momentum transfer was probed by comparing the experimental angular distributions of the outgoing tritons to calculated distorted wave Born approximation curves. The angular distributions of the outgoing tritons populating the peak-like structure are remarkably similar in the two reactions and are significantly different from the angular distributions associated with the nearby continuum region. Relative partial cross sections for the observed levels, angle averaged between 34 and 58 degrees, were measured. In ${}^{150}\mathrm{Sm}$, 39(4)% of the strength of the peak-like structure could be accounted for by the observed discrete states. This compares with a value of 93(15)% for ${}^{152}\mathrm{Sm}$.

The nuclear charge radius is a fundamental property of an atomic nucleus. In this article we study the predictive power of empirical relations for experimental nuclear charge radii of neighboring nuclei and predict the unknown charge radii of 1085 nuclei based on the experimental CR2013 database within an uncertainty of 0.03 fm.

$\gamma$ rays following the EC/${\beta }^{+}$ and $\alpha$ decay of the $N$ = 126, ${}^{213}\mathrm{Fr}$ nucleus have been observed at the CERN isotope separator on-line (ISOLDE) facility with the help of $\gamma$-ray and conversion-electron spectroscopy. These $\gamma$ rays establish several hitherto unknown excited states in ${}^{213}\mathrm{Rn}$. Also, five new $\alpha$-decay branches from the ${}^{213}\mathrm{Fr}$ ground state have been discovered. Shell model calculations have been performed to understand the newly observed states in ${}^{213}\mathrm{Rn}$.

Quasi-elastic scattering and transfer angular distributions for ${}^{10,11}\mathrm{B}+{}^{232}\mathrm{Th}$ reactions have been measured simultaneously in a wide range of bombarding energies around the Coulomb barrier. The quasi-elastic angular distribution data are analyzed using the optical model code ecis with phenomenological Woods-Saxon potentials. The obtained potential parameters suggest the presence of usual threshold anomaly, confirming tightly bound characteristics for both the projectiles. The reaction cross sections are obtained from the fitting of quasi-elastic angular distribution data. The reduced cross sections at sub-barrier energies compared with ${}^{6,7}\mathrm{Li}+{}^{232}\mathrm{Th}$ systems show a systematic dependence on projectile breakup energy. The angular distribution of the transfer products show similar behavior for both the systems.

The one-dimensional non-boost-invariant evolution of the quark-gluon plasma, presumably produced during the early stages of heavy-ion collisions, is analyzed within the frameworks of viscous and anisotropic hydrodynamics. We neglect transverse dynamics and assume homogeneous conditions in the transverse plane but, differently from Bjorken expansion, we relax longitudinal boost invariance in order to study the rapidity dependence of various hydrodynamical observables. We compare the results obtained using several formulations of second-order viscous hydrodynamics with a recent approach to anisotropic hydrodynamics, which treats the large initial pressure anisotropy in a nonperturbative fashion. The results obtained with second-order viscous hydrodynamics depend on the particular choice of the second-order terms included, which suggests that the latter should be included in the most complete way. The results of anisotropic hydrodynamics and viscous hydrodynamics agree for the central hot part of the system, however, they differ at the edges where the approach of anisotropic hydrodynamics helps to control the undesirable growth of viscous corrections observed in standard frameworks.

With the chiral quark model, we have calculated the axial charges of the pentaquark states with $(I,I_3)=\left(\frac{1}{2},\frac{1}{2}\right)$ and $J^P={\frac{1}{2}}^{\pm }, {\frac{3}{2}}^{\pm }$, and ${\frac{5}{2}}^{\pm }$. The $P_c$ states with the same $J^P$ quantum numbers but different color-spin-flavor configurations have very different axial charges, which encode important information on their underlying structures. For some of the $J^P={\frac{3}{2}}^{\pm }$ or ${\frac{5}{2}}^{\pm }$ pentaquark states, their axial charges are much smaller than that of the proton.

The mechanism of fusion hindrance, an effect preventing the synthesis of superheavy elements in the reactions of cold and hot fusion, is investigated using the Boltzmann-Uehling-Uhlenbeck equation, where Coulomb interaction is introduced. A strong sensitivity is observed both to the modulus of incompressibility of symmetric nuclear matter, controlling the competition of surface tension and Coulomb repulsion, and to the stiffness of the density-dependence of symmetry energy, influencing the formation of the neck prior to scission. The experimental fusion probabilities were for the first time used to derive constraints on the nuclear equation of state. A strict constraint on the modulus of incompressibility of nuclear matter $K_0=240–260$ MeV is obtained while the stiff density-dependences of the symmetry energy ($\gamma >1$) are rejected.

An antisymmetrized molecular dynamics model (AMD-FM), modified to take into account the Fermi motion explicitly in its nucleon-nucleon collision process, is presented. Calculated high-energy proton spectra are compared with those of ${}^{40}\mathrm{Ar}+{}^{51}\mathrm{V}$ at 44 MeV/nucleon from Coniglione et al. [Phys. Lett. B 471, 339 (2000)] and those of ${}^{36}\mathrm{Ar}+{}^{181}\mathrm{Ta}$ at 94 MeV/nucleon from Germain et al. [Nucl. Phys. A 620, 81 (1997)]. Both of the experimental data are reasonably well reproduced by the newly added Fermi boost in the nucleon-nucleon collision process without additional processes, such as a three-body collision or a short-range correlation. The production mechanism of high-energy protons in intermediate-energy heavy-ion collisions is discussed.

Excited states in the neutron-deficient $N=84$ nuclide ${}^{155}\mathrm{Lu}$ have been populated by using the ${}^{102}\mathrm{Pd}({}^{58}\mathrm{Ni},\alpha \mathrm{p})$ reaction. The ${}^{155}\mathrm{Lu}$ nuclei were separated by using the gas-filled recoil ion transport unit (RITU) separator and implanted into the Si detectors of the gamma recoil electron alpha tagging (GREAT) spectrometer. Prompt $\gamma$-ray emissions measured at the target position using the JUROGAM Ge detector array were assigned to ${}^{155}\mathrm{Lu}$ through correlations with $\alpha$ decays measured in GREAT. Structures feeding the $(11/2^{-})$ and $(25/2^{-})\alpha$-decaying states have been revised and extended. Shell-model calculations have been performed and are found to reproduce the excitation energies of several of the low-lying states observed to within an average of 71 keV. In particular, the seniority inversion of the $25/2^{-}$ and $27/2^{-}$ states is reproduced.

The dipole excitations for calcium and zirconium isotopes are studied within the fully self-consistent Hartree-Fock mean field incorporated with the renormalized random-phase approximation (RRPA) using the Skyrme interaction SLy5. The RRPA takes into account the effect of ground-state correlations beyond RPA owing to the Pauli principle between the particle-hole pairs that form the RPA excitations as well as the correlations due to the particle-particle and hole-hole transitions, whose effects are treated here in an effective way. By comparing the RPA results with the RRPA ones, which are obtained for isoscalar (IS) and isovector (IV) dipole excitations in ${}^{48,52,58}\mathrm{Ca}$ and ${}^{90,96,110}\mathrm{Zr}$, it is shown that ground-state correlations beyond the RPA reduce the IS transition strengths. They also shift up the energy of the lowest IV dipole state and slightly push down the peak energy of the IV giant dipole resonance. As the result, the energy-weighted sums of strengths of both IS and IV modes decrease, causing the violation of the corresponding energy-weighted sum rules (EWSR). It is shown that this sum rule violation can be eliminated by taking into account the contribution of the particle-particle and hole-hole excitations together with the particle-hole ones in a simple and perturbative way. Consequently, the ratio of the energy-weighted sum of strengths of the pygmy dipole resonance to that of the giant dipole resonance increases.