Mapping out the equation of state of nuclear matter is a long-standing problem in nuclear physics. Recent emphasis is on the density dependence of the symmetry energy, with experiments needing dedicated symmetry-energy observables. Towards the latter goal, we employ the Boltzmann-Uehling-Uhlenbeck (pBUU) transport model to simulate pion production in a heavy ion collision. We find that the net pion yield tests the momentum dependence of the nuclear mean field. In exploring the sensitivity of pion observables to the symmetry energy at higher than normal densities, we find that our calculations of pion ratios contradict, at some level, predictions from both the isospin-dependent BUU (IBUU) and improved isospin-dependent quantum molecular dynamics models. We propose to employ the pion ratio in the high-energy tail of spectra in future experiments to distinguish between different variants of high-density symmetry energy.

The upcoming Facility for Rare Isotope Beams (FRIB) at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University has reemphasized the importance of accurate modeling of low energy nucleus-nucleus scattering. Such calculations have been simplified by using the eikonal approximation. As a high energy approximation, however, its accuracy suffers for the medium energy beams that are of current experimental interest. A prescription developed by Wallace [Phys. Rev. Lett. 27, 622 (1971) and Ann. Phys. (NY) 78, 190 (1973)] that obtains the scattering propagator as an expansion around the eikonal propagator (Glauber approach) has the potential to extend the range of validity of the approximation to lower energies. Here we examine the properties of this expansion, and calculate the first-, second-, and third-order corrections for the scattering of a spinless particle off of a ${}^{40}\mathrm{Ca}$ nucleus, and for nuclear breakup reactions involving ${}^{11}\mathrm{Be}$. We find that, including these corrections extends the lower bound of the range of validity down to energies as low as about 45 MeV. At that energy the corrections provide as much as a 15% correction to certain processes.

Although asymptotic freedom is an essential feature of QCD, it is absent in effective chiral quark models like the Nambu–Jona-Lasinio and linear sigma models. In this work we advocate that asymptotic freedom plays a key role in the recently observed discrepancies between results of lattice QCD simulations and quark models regarding the behavior of the pseudocritical temperature $T_{pc}$ for chiral-symmetry restoration in the presence of a magnetic field $B$. We show that the lattice predictions that $T_{pc}$ decreases with $B$ can be reproduced within the Nambu–Jona-Lasinio model if the coupling constant $G$ of the model decreases with $B$ and the temperature. Without aiming at numerical precision, we support our claim by considering a simple ansatz for $G$ that mimics the asymptotic-freedom behavior of the QCD coupling constant $1/{\alpha }_s\sim ln(eB/{\Lambda }_{\text{QCD}}^2)$ for large values of $B$.

Systematic investigations of the electric dipole $\left(E1\right)$ modes of excitation are performed using the canonical-basis time-dependent Hartree-Fock-Bogoliubov (Cb-TDHFB) theory. The Cb-TDHFB is able to describe dynamical pairing correlations in excited states of nuclear systems. We apply the method to the real-time calculation of linear response in even-even nuclei with Skyrme functionals. Effects of shell structure, neutron skin, deformation, and neutron chemical potential (separation energy) are studied in a systematic way. This reveals a number of characteristic features of the low-energy $E1$ modes. We also find a universal behavior in the low-energy $E1$ modes for heavy neutron-rich isotopes, which suggests the emergence of decoupled $E1$ peaks beyond $N=82$.

In this work we calculate the interaction cross sections of neon isotopes (${}^{17–32}$Ne) on ${}^{12}\mathrm{C}$ at 240 and 950 MeV/nucleon within the framework of the Coulomb-modified correlation expansion for the Glauber model $S$ matrix. The calculations involve (i) up to the two-body density term in the correlation expansion, (ii) the relativistic mean-field (RMF) densities for the colliding nuclei, and (iii) the single Gaussian approximation for the nucleon-nucleon (NN) amplitude. To test the halo structure, the extended neutron density distribution for ${}^{31}\mathrm{Ne}$ is also used. Our results, using RMF densities, are in close agreement with the available experimental data at 240 MeV/nucleon except for ${}^{31}\mathrm{Ne}$, for which the extended neutron density distribution is found to play an important role in explaining the data, thereby supporting a halo structure in ${}^{31}\mathrm{Ne}$. The corresponding results at 950 MeV/nucleon are, however, not as satisfactory as those obtained at 240 MeV/nucleon. The results also demonstrate the importance of the two-body density term in the present calculations.

The neutron capture reaction is investigated. The three major reaction mechanisms, namely, compound-nucleus capture (CNC), pre-equilibrium capture (PEC), and direct capture (DIC), are considered on the basis of the Hauser–Feshbach model, the exciton model, and potential model, respectively. The three mechanisms are treated simultaneously and consistently, i.e, they are obtained on the basis of the same nuclear ingredients, such as the optical potential and nuclear-level densities. In this framework, the three components are calculated on the same footing and represent partial fluxes of the same total reaction cross section. The total neutron-capture cross sections and astrophysical reaction rates are calculated within the updated modern reaction code talys for about 8000 nuclei with $8\le Z\le 110$ lying between the proton and neutron drip lines. The nuclear-structure ingredients involved in the calculation are determined from experimental data whenever available and, if not, from global microscopic nuclear models. For the targets with mass number $A>26$, a fair agreement between the computed total-capture cross sections and experimental data is found but, for the lightest nuclei, only the predicted DIC cross sections reproduce the experimental results satisfactorily. Significant and even dominant contribution to the total reaction rate comes from the DIC component for neutron-rich nuclei, especially in the $Z=50–70$ region. The impact of the newly determined reaction rates on the r process abundances resulting from the ejection of matter in neutrino-driven winds or the decompression of neutron star matter is investigated.

In real-time thermal field theory, the standard expression of shear viscosity for nucleonic constituents is derived from the two-point function of nucleonic viscous stress tensors at finite temperature and density. The finite thermal width or Landau damping is traditionally included in the nucleon propagators. This thermal width is calculated from the in-medium self-energy of nucleons for different possible pion-baryon loops. The dynamical part of nucleon-pion-baryon interactions are accounted for by the effective Lagrangian densities of standard hadronic model. The shear viscosity to entropy density ratio of the nucleonic component decreases with the temperature and increases with the nucleon chemical potential. However, adding the contribution of the pionic component, the total viscosity to entropy density ratio also reduces with the nucleon chemical potential when the mixing effect between pion and nucleon components in the mixed gas is considered. Within the hadronic domain, the viscosity to entropy density ratio of the nuclear matter gradually reduces as temperature and nucleon chemical potential increase and therefore the nuclear matter is approaching the (nearly) perfect-fluid state.

The eikonal reaction theory (ERT) proposed lately is a method of calculating one-neutron removal reactions at intermediate incident energies in which Coulomb breakup is treated accurately with the continuum discretized coupled-channels method. ERT is extended to two-neutron removal reactions. ERT reproduces measured one- and two-neutron removal cross sections for ${}^6\mathrm{He}$ scattering on ${}^{12}\mathrm{C}$ and ${}^{208}\mathrm{Pb}$ targets at 240 MeV/nucleon and also on a ${}^{28}\mathrm{Si}$ target at 52 MeV/nucleon. For the heavier target in which Coulomb breakup is important, ERT yields much better agreement with the measured cross sections than the Glauber model.

The formation of Mach cones is studied in a full $(3+1)$-dimensional setup of ultrarelativistic heavy-ion collisions, considering a transverse and longitudinal expanding medium at Relativistic Heavy-Ion Collider energies. For smooth initial conditions and central collisions the jet-medium interaction is investigated using high-energy jets and various values of the ratio of shear viscosity over entropy density, $\eta /s$. For small viscosities, the formation of Mach cones is proven, whereas for larger viscosities the characteristic structures smear out and vanish eventually. The formation of a double-peak structure both in a single- and in a multiple-jet event is discussed.

In the article by Adhikari, Cohen, Ayyagari, and Strother [Phys. Rev. C 83, 065201 (2011)] the description of dense nuclear matter by means of Skyrmions in hyperspherical unit cells is severely criticized. I point out that this criticism is based on invalid assumptions and therefore unwarranted.

Measurements were made of the differential cross section of the resonant reactions ${}^4\mathrm{He}({}^{14}\mathrm{N},\alpha )$ and, ${}^4\mathrm{He}({}^{14}\mathrm{N},d){}^{16}\mathrm{O}$ with the intention of investigating the compound nucleus ${}^{18}\mathrm{F}$. These measurements were performed in inverse kinematics at a center-of-mass scattering angle of ${\theta }_{\mathrm{c}.\mathrm{m}.}={180}^{\circ }$ by using a thick ${}^4\mathrm{He}$ gas target and a ${}^{14}\mathrm{N}$ beam. Data were recorded which covered ${}^{18}\mathrm{F}$ excitation energies from 5.5–16 MeV. An $R$-matrix analysis was performed on the data up to 9 MeV, and the energies, spins, parities, and partial widths were extracted. Nine new states have been identified in ${}^{18}\mathrm{F}$ based on this analysis between 8.326 and 8.915 MeV.

We propose a new parametrization of the distribution of the initial eccentricity in a nucleus-nucleus collision at a fixed centrality, which we name the elliptic power distribution. It is a two-parameter distribution, where one of the parameters corresponds to the intrinsic eccentricity, while the other parameter controls the magnitude of eccentricity fluctuations. Unlike the previously used Bessel-Gaussian distribution, which becomes worse for more peripheral collisions, the new elliptic power distribution fits several Monte Carlo models of the initial state for all centralities.

If the observed quasi-periodic oscillations in magnetar flares are partially confined to the crust, then the oscillation frequencies are unique probes of the nuclear physics of the neutron star crust. We study crustal oscillations in magnetars including corrections for a finite Alfvén velocity. Our crust model uses a new nuclear mass formula that predicts nuclear masses with an accuracy very close to that of the finite range droplet model. This mass model for equilibrium nuclei also includes shell corrections and an updated neutron-drip line. We perturb our crust model to predict axial crust modes and assign them to observed giant flare quasi-periodic oscillation frequencies from the soft $\gamma$-ray repeater SGR 1806-20. We find magnetar crusts that match observations for various magnetic field strengths, entrainment of the free neutron gas in the inner crust, and crust-core transition densities. We find that observations can be reconciled with smaller values of the symmetry energy slope parameter, $L$, if there is a significant amount of entrainment of the neutrons by the superfluid or if the crust-core transition density is large. We also find neutron star masses and radii which are in agreement with expectations from what is known about low-density matter from nuclear experiment. Matching observations with a field-free model we obtain the approximate values of $M=1.35M_{\odot }$ and $R=11.9\mathrm{km}$. Matching observations using a model with the surface dipole field of SGR 1806-20 $\left(B=2.4\times {10}^{15}\mathrm{G}\right)$ we obtain the approximate values of $M=1.25M_{\odot }$ and $R=12.4\mathrm{km}$.

The masses of ${}^{222,224,226\text{–}233}\mathrm{Fr}$ and ${}^{233,234}\mathrm{Ra}$ have been determined with the Penning-trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN, including the previously unknown mass and half-life of ${}^{233}\mathrm{Fr}$. We study the evolution of the odd-even staggering of binding energies along the francium and radium isotopic chains and of its lowest-order estimator, ${\Delta }^3\left(N\right)$. An enhancement of the staggering of ${\Delta }^3\left(N\right)$ is observed towards neutron number $N=146$, which points to contributions beyond pairing correlations. These contributions are investigated in the Hartree-Fock and Hartree-Fock-Bogoliubov approaches, emphasizing the connections to the single-particle level density and nuclear deformation.

We study in this work the preference of the arrangements of fragments leading to ternary fission. Earlier experimental investigations on this subject have established the fact that the emission of a third particle happens in a direction perpendicular to the direction of the fission axis. Recently, within the missing mass approach, it has been reported that for fragments of comparable masses, the so-called collinear cluster tripartition (CCT), collinear emission of the fragments occurs. The ternary potential energy surface (PES) of three-body fragmentation of ${}^{252}\mathrm{Cf}$ is studied. The PESs are calculated for the fragment arrangements starting from a collinear configuration to a triangular configuration by varying the angle between the end fragments with respect to the fragment positioned in the middle. Furthermore, the role of the positioning of the three fragments is analyzed. Our results indicate that there is a clear preference for an arrangement in which the lightest fragment is positioned in the middle. Furthermore, for all possible third fragments, collinear geometry is found to be favored over orthogonal geometry.

Excitation functions for shell-stabilized evaporation residues produced in ${}^{48}\mathrm{Ca}$-induced reactions with ${}^{154}\mathrm{Gd},{}^{159}\mathrm{Tb},{}^{162}\mathrm{Dy}$, and ${}^{165}\mathrm{Ho}$ targets have been measured in experiments performed at the Cyclotron Institute at Texas A&M University. The examined energy range predominantly covers the $3n$ and $4n$ evaporation channels with higher cross sections measured for the $4n$ products. The ${\sigma }_{4n}$ are nearly invariant within experimental uncertainty in reactions with ${}^{159}\mathrm{Tb},{}^{162}\mathrm{Dy}$, and ${}^{165}\mathrm{Ho}$ with the maxima at 12.6 ± 1.9, 12.6 ± 1.7, and 9.4 ± 1.3 mb, respectively. For the reaction with ${}^{154}\mathrm{Gd}$, the maximum is slightly lower at 4.0 ± 0.6 mb. A simple model to describe the measured production cross sections was employed. Capture was estimated by using the “diffused barrier formula” from the “fusion by diffusion” model proposed by Świątecki et al. [Phys. Rev. C 71, 014602 (2005)]. The fusion probability was estimated by using a phenomenological expression presented by Siwek-Wilczyńska et al. [Int. J. Mod. Phys. E 17, 12 (2008)]. The survival probability was calculated according to the formula of Vandenbosch and Huizenga [Nuclear Fission (Academic, New York, 1973)], derived from transition-state theory. The best agreement is reached between calculation and experiment upon inclusion of collective effects in the calculation of the survival probability, shown previously to be important for production of weakly deformed nuclei. This, in turn, challenges the expectation that strong shell stabilization benefits the production cross section. The present data are compared with earlier studies on production of neutron-deficient nuclei in Ca-induced reactions with lanthanide targets.

We use a nonlinear response formalism to describe the Event-plane correlations measured by the ATLAS Collaboration. With one exception $\left(〈cos(2{\Psi }_2-6{\Psi }_3+4{\Psi }_4)〉\right)$, the Event-plane correlations are qualitatively reproduced by considering the linear and quadratic response to the lowest cumulants. For the lowest harmonics such as $〈cos(2{\Psi }_2+3{\Psi }_3-5{\Psi }_5)〉$, the correlations are quantitatively reproduced, even when the naive Glauber model prediction has the wrong sign relative to experiment. The quantitative agreement for the higher plane correlations (especially those involving ${\Psi }_6$) is not as good. The centrality dependence of the correlations is naturally explained as an average of the linear and quadratic response.

We calculate the in-medium masses of the bottomonium states $\left[{\rm Y}\right(1S),{\rm Y}(2S),{\rm Y}(3S)$, and ${\rm Y}\left(4S\right)]$ in isospin asymmetric strange hadronic matter at finite temperatures. The medium modifications of the masses arise due to the interaction of these heavy quarkonium states with the gluon condensates of QCD. The gluon condensates in the hot hadronic matter are computed from the medium modification of a scalar dilaton field within a chiral SU(3) model, introduced in the hadronic model to incorporate the broken scale invariance of QCD. There is seen to be a drop in the masses of the bottomonium states and mass shifts are observed to be quite considerable at high densities for the excited states. The effects of density, isospin asymmetry, strangeness, as well as temperature of the medium on the masses of the ${\rm Y}$ states are investigated. The effects of the isospin asymmetry as well as strangeness fraction of the medium are seen to be appreciable at high densities and small temperatures. The density effects are the most dominant medium effects which should have observable consequences in the compressed baryonic matter (CBM) in the heavy ion collision experiments in the future facility at FAIR, GSI. The study of the ${\rm Y}$ states will, however, require access to energies higher than the energy regime planned at CBM experiment. The density effects on the bottomonium masses should also show up in the dilepton spectra at the Super Proton Synchrotron (SPS) energies, especially for the excited states for which the mass drop is observed to quite appreciable.

Background: Gamow-Teller (GT) transition strengths are key inputs for estimating weak reaction rates of importance for a wide variety of astrophysical applications. $\left(n,p\right)$-type charge-exchange reactions, such as the $(t,{}^3\mathrm{He})$ reaction used in this work, are commonly used for extracting the GT strength distribution in the ${\beta }^{+}$ (electron-capture) direction. Such studies are important for testing theoretical models used to estimate weak rates for a large number of nuclei for simulations of astrophysical phenomena.

Purpose: The ${}^{56}\mathrm{Fe}(t,{}^3\mathrm{He})$ reaction at 115 $A$MeV was measured in order to extract GT strengths for transitions to ${}^{56}\mathrm{Mn}$. The extracted strength distributions were compared with shell-model calculations in the $pf$-shell model space using the KB3G and GXPF1a interactions, and with calculations in the quasi-particle random-phase approximation (QRPA).

Method: Differential cross sections and excitation-energy spectra for the ${}^{56}\mathrm{Fe}(t,{}^3\mathrm{He})$ reaction were determined by measuring the trajectories of ${}^3\mathrm{He}$ ejectiles through the S800 magnetic spectrograph and deducing their momenta. Contributions corresponding to GT transitions were isolated by using a multipole decomposition analysis. A well-established proportionality between GT strength and differential cross section at zero-linear-momentum transfer was utilized to convert extracted cross sections to GT strengths.

Results and Conclusions: GT transition strengths from ${}^{56}\mathrm{Fe}$ to ${}^{56}\mathrm{Mn}$ were extracted up to an excitation energy of 10 MeV. Shell-model calculations with the GXPF1a interaction reproduced the observed GT strength distribution slightly better than calculations with the KB3G interaction. The calculated strength distribution in the QRPA did not reproduce the observed strength distribution. The new experimental data have an improved precision at low excitation energies compared to previous results obtained from an ${}^{56}\mathrm{Fe}\left(n,p\right)$ experiment. Electron-capture rates based on the experimental and theoretical Gamow-Teller strengths were compared and deviations were included in an assessment of the validity of electron-capture rates based on theoretical models for nuclei in the $pf$ shell.

We study an exact and extended solution of the fluid dynamical model of heavy ion reactions and estimate the rate of slowing down of the rotation due to the longitudinal and transverse expansion of the system. The initial state parameters of the model are set on the basis of a realistic $(3+1)$-dimensional fluid dynamical calculation at TeV energies, where the rotation is enhanced by the buildup of the Kelvin-Helmholtz instability in the flow.