In this paper details of the experimental procedure and data analysis of the collision of ${}^{11}\mathrm{Be}{+}^{64}$Zn around the Coulomb barrier are described and discussed in the framework of different theoretical approaches. In a previous work [A. Di Pietro et al., Phys. Rev. Lett. 105, 022701 (2010).], the elastic scattering angular distribution of the collisions ${}^{9,10}\mathrm{Be}{+}^{64}$Zn as well as the angular distribution for the quasielastic scattering and transfer/breakup cross sections for the ${}^{11}\mathrm{Be}{+}^{64}$Zn reaction were briefly reported. The suppression of the quasielastic angular distribution in the Coulomb-nuclear interference angular region observed in the collision of the ${}^{11}$Be halo nucleus with respect to the other two beryllium isotopes was interpreted as being caused by a long-range absorption owing to the long decay length of the ${}^{11}$Be wave function. In this paper, new continuum-discretized coupled-channel calculations of the ${}^{11}\mathrm{Be}{+}^{64}$Zn reaction are reported in the attempt to interpret the effect of coupling with the breakup channels on the measured cross sections. The calculations show that the observed suppression of the Coulomb-nuclear interference peak is caused by a combined effect of Coulomb and nuclear couplings to the breakup channels.

We present simultaneously measured barrier distributions for the ${}^{20}$Ne $+$ ${}^{208}$Pb system derived from large-angle quasielastic scattering and fusion, in the latter case by means of the detection of fission fragments. Both distributions turned out to be smooth, in spectacular disagreement with the results of standard coupled-channels calculations. Namely, they do not posses the strong structure expected from coupled-channels calculations, even if apparently they take into account explicitly all relevant strong couplings. This points to the importance of weak channels, i.e., transfer reactions and scattering connected with noncollective excitations.

We develop the relativistic theory of hydrodynamic fluctuations for application to high-energy heavy-ion collisions. In particular, we investigate their effect on the expanding boost-invariant (Bjorken) solution of the hydrodynamic equations. We discover that correlations over a long rapidity range are induced by the propagation of the sound modes. Due to the expansion, the dispersion law for these modes is nonlinear and attenuated even in the limit of zero viscosity. As a result, there is a nondissipative wake behind the sound front which is generated by any instantaneous pointlike fluctuation. We evaluate the two-particle correlators using the initial conditions and hydrodynamic parameters relevant for heavy-ion collisions at RHIC and LHC. In principle these correlators can be used to obtain information about the viscosities because the magnitudes of the fluctuations are directly proportional to them.

A very important open question related to the pygmy dipole resonance refers to its quite elusive collective nature. In this paper, within a harmonic oscillator shell model, generalizing an approach introduced by Brink, we first identify the dipole normal modes in neutron-rich nuclei and derive the energy-weighted sum rule exhausted by the pygmy dipole resonance. Then, by solving numerically the self-consistent Landau-Vlasov kinetic equations for neutrons and protons with specific initial conditions, we explore the structure of the different dipole vibrations in the ${}^{132}\text{Sn}$ system and investigate their dependence on the symmetry energy. We evidence the existence of a distinctive collective isoscalar-like mode with an energy well below the giant dipole resonance (GDR), which is very weakly dependent on the isovector part of the nuclear effective interaction. At variance with this, its corresponding strength is rather sensitive to the behavior of the symmetry energy below saturation, which rules the number of excess neutrons in the nuclear surface.

There are some discrepancies in the low-energy data on the photoabsorption cross section of ${}^4$He. We calculate the cross section with realistic nuclear forces and explicitly correlated Gaussian functions. Final-state interactions and two- and three-body decay channels are taken into account. The cross section is evaluated using two methods: With the complex scaling method the total absorption cross section is obtained up to the rest energy of a pion, and with the microscopic $R$-matrix method cross sections for both ${}^4$He($\gamma ,p$)${}^3$H and ${}^4$He($\gamma ,n$)${}^3$He are calculated below 40 MeV. Both methods give virtually the same result. The cross section rises sharply from the ${}^3\text{H}+p$ threshold, reaching a giant resonance peak at 26–27 MeV. Our calculation reproduces almost all the data above 30 MeV. We stress the importance of ${}^3\mathrm{H}+p$ and ${}^3\mathrm{He}+n$ cluster configurations on the cross section as well as the effect of the one-pion exchange potential on the photonuclear sum rule.

In this paper we predict atomic masses which are not experimentally accessible by using local mass relations which connect with the proton-neutron interactions with improved accuracy. Based on our predicted masses, we investigate one-proton and one-neutron drip lines for a few regions in the nuclide chart and $\alpha$-decay half-lives times for some isotopes with proton number $102⩽Z⩽106$. The impact of our predicted one-neutron separation energies on astrophysical $r$-process nucleosynthesis is discussed within the framework of a classical $r$-process model.

A recent experiment located the lowest 2${}^{+}$ state in ${}^{20}$Mg and discovered that the corresponding 2${}^{+}$, $T$ $=$ 2 state in ${}^{20}$F does not fit expectations of the isobaric multiplet mass equation without a $d$ term. We have calculated the energies of the ground and 2${}^{+}$ states in ${}^{20}$Mg and the 2${}^{+}$ in ${}^{20}$F in a potential model, using shell-model spectroscopic factors. We conclude that this important ${}^{20}$F state has likely never been observed, and suggest a reaction to find it.

To further our understanding of the influence of weakly coupled channels on the distribution of Coulomb barrier heights, we have measured transfer cross sections for ${}^{20}$Ne ions backscattered from ${}^{\mathrm{nat}}$Ni, ${}^{118}$Sn, and ${}^{208}$Pb targets at near-barrier energies. The $Q$ value spectrum in the case of ${}^{208}$Pb target has been determined too. The transfer channels appear to be especially important for ${}^{208}$Pb, whose double-closed-shell nature leads to a relatively low level density for noncollective inelastic excitations.

The basic aim of the present study is to investigate the role of deformations, orientations, angular momentum dependence along with possible presence of noncompound nucleus (nCN) component in the decay of preactinide nucleus ${}^{204}$Po${}^{*}$ formed in ${}^{16}$O and ${}^{28}$Si induced reactions over a wide range of projectile energies having comparable $E_{\mathrm{c}.\mathrm{m}.}/V_c$ values for two channels. Recently, an experiment was performed to extract fusion-fission and evaporation residue cross sections for ${}^{16}$O + ${}^{188}$O $\to$ ${}^{204}$Po${}^{*}$ and ${}^{28}$Si + ${}^{176}$Yb $\to$ ${}^{204}$Po${}^{*}$ reactions over a wide range of energies ($E_{\mathrm{lab}}=84$–155 MeV). Within the dynamical cluster decay model (DCM), we have calculated the evaporation residue and the fission cross sections in reference to the available data at various incident energies by simultaneously fitting the only parameter, neck-length ($\Delta R$) for evaporation residue and fission. The choice of different neck-length parameter ($\Delta R$) values for ER and fission indicate that the two decay processes do not occur simultaneously, i.e., they occur in different time scales and evolve subject to the nature of dynamics of compound nucleus formed. The effects of nuclear deformations and orientations are duely incorporated in the framework of DCM and role of ${\beta }_2$ deformations is investigated in reference to decay path of ${}^{204}$Po${}^{*}$ nucleus. The calculated evaporation residue cross sections and fission cross sections show excellent agreement with the reported data at all incident center of mass energies, except at one highest energy for the channel ${}^{28}$Si + ${}^{176}$Yb $\to$ ${}^{204}$Po${}^{*}$ for fission. The disagreement between DCM calculations and reported data at highest incident center of mass energy for the ${}^{28}$Si + ${}^{176}$Yb entrance channel may be associated with the presence of small amount of nCN effects which is in line with the predictions of the preequilibrium model. Also the in-built property of barrier lowering effect of DCM seems to be operating in context of these reactions. The fission fragment anisotropies are also calculated using DCM-based parameters for the nonsticking moment of inertia, and they find reasonable comparison with experimental data. Finally, the isotopic effect is worked out by studying the decay of ${}^{202}$Po${}^{*}$ and ${}^{204}$Po${}^{*}$ nuclei formed in ${}^{16}$O induced reactions at comparable $E_{\mathrm{c}.\mathrm{m}.}/V_c$ value.

Inclusive cross sections ${\sigma }^A=E{d}^3\sigma (X,P_t^2)/d^{3}p$ of antiproton and negative pion production on Be, Al, Cu, and Ta targets hit by 10-GeV protons were measured at the laboratory angles of 10.5${}^{\circ }$ and 59${}^{\circ }$. Antiproton cross sections were obtained in both kinematically allowed and kinematically forbidden regions for antiproton production on a free nucleon. The antiproton cross-section ratio as a function of the longitudinal variable $X$ exhibits three separate plateaus, which gives evidence for the existence of compact baryon configurations in nuclei—small-distance scaled objects of nuclear structure. The comparability of the measured cross-section ratios with those obtained in the inclusive electron scattering off nuclei suggests weak antiproton absorption in nuclei. Observed behavior of the cross-section ratios is interpreted in the framework of a model considering the hadron production as a fragmentation of quarks (antiquarks) into hadrons. It has been established that the antiproton formation length in nuclear matter can reach the magnitude of 4.5 fm.

Parameterizing the charm and anticharm quark momentum distributions by the Tsallis distribution, we study the nonequilibrium effect on the charmonium production rate in a quark-gluon plasma up to the next-to-leading order in perturbative QCD. We find that nonequilibrium charm and anticharm quarks suppress the charmonium production rate compared to that from equilibrated ones. We further show that the suppression factor calculated with the charm quark relaxation time, which has frequently been used in the literature, is close to our results.

Fusion excitation functions for the reactions of ${}^{124,132}$Sn with ${}^{40,48}$Ca were measured at energies near and below the Coulomb barrier. Weak sub-barrier fusion enhancement accounted for by coupling to the first 2${}^{+}$ and 3${}^{-}$ states in the target and projectile was observed for ${}^{124,132}\text{Sn}+{}^{48}\text{Ca}$. However, the ${}^{124,132}\text{Sn}+{}^{40}\text{Ca}$ fusion cross sections are very strongly enhanced below the barrier and this difference survives even after correcting for trivial size effects. Although the enhancement appears to be related to the existence of large positive $Q$ values for neutron transfer reactions, it is not proportional to the magnitudes of those $Q$ values, which are much larger for ${}^{132}\mathrm{Sn}+{}^{40}\mathrm{Ca}$ than for ${}^{124}\mathrm{Sn}+{}^{40}\mathrm{Ca}$.

A complete calculation of the pion-nucleon loops that contribute to the transition operator for $NN\to NN\pi$ up-to-and-including next-to-next-to-leading order (N${}^2$LO) in chiral effective field theory near threshold is presented. The evaluation is based on the so-called momentum counting scheme, which takes into account the relatively large momentum of the initial nucleons inherent in pion-production reactions. We show that the significant cancellations between the loops found at next-to-leading order (NLO) in the earlier studies are also operative at N${}^2$LO. In particular, the $1/m_N$ corrections (with $m_N$ being the nucleon mass) to loop diagrams cancel at N${}^2$LO, as do the contributions of the pion loops involving the low-energy constants $c_i$, $i=1,...,4$. In contrast to the NLO calculation however, the cancellation of loops at N${}^2$LO is incomplete, yielding a nonvanishing contribution to the transition amplitude. Together with the one-pion exchange tree-level operators, the loop contributions provide the long-range part of the production operator. Finally, we discuss the phenomenological implications of these findings. In particular, we find that the amplitudes generated by the N${}^2$LO pion loops yield contributions comparable in size with the most important phenomenological heavy-meson exchange amplitudes.

We discuss a variational calculation for nuclear shell-model calculations and propose a new procedure for the energy-variance extrapolation (EVE) method using a sequence of the approximated wave functions obtained by the variational calculation. The wave functions are described as linear combinations of the parity, angular-momentum projected Slater determinants, the energy of which is minimized by the conjugate gradient method obeying the variational principle. The EVE generally works well using the wave functions, but we found some difficult cases where the EVE gives a poor estimation. We discuss the origin of the poor estimation concerning shape coexistence. We found that the appropriate reordering of the Slater determinants allows us to overcome this difficulty and to reduce the uncertainty of the extrapolation.

We calculate reduced $B\left(E2\right)$ and $B\left(M1\right)$ electromagnetic transition strengths within and between $K$ bands in support of a recently proposed model for the structure of heavy nuclei. Previously, only spectra and a rough indication of the largest $B\left(E2\right)$ strengths were reported. The present more detailed calculations should aid the experimental identification of the predicted $0^{+}$, $1^{+}$, and $2^{+}$ bands and, in particular, act to confirm or refute the suggestion that the model $0^{+}$ and $2^{+}$ bands correspond to the well known and widespread beta and gamma bands. Furthermore they pinpoint transitions that can indicate the presence of a so-far elusive $1^{+}$ band by feeding relatively strongly into or out of it. Some of these transitions may already have been measured in ${}^{230}$Th, ${}^{232}$Th, and ${}^{238}$U.

Despite the supposed simplicity of double-closed shell nuclei, conventional coupled-channels calculations, that include all of the known collective states of the target and projectile, give a poor fit to the fusion cross section for the ${}^{16}$O + ${}^{208}$Pb system. The discrepancies are highlighted through the experimental barrier distribution and logarithmic derivative, that are both well defined by the precise experimental fusion data available. In order to broaden our search for possible causes for this anomaly, we revisit this system and include in our calculations a large number of noncollective states of the target, whose spin, parity, excitation energy, and deformation parameter are known from high-precision proton inelastic-scattering measurements. Although the new coupled-channels calculations modify the barrier distribution, the disagreement with experiment remains both for fusion and for quasi-elastic (QE) scattering. We find that the $Q$-value distributions for large-angle QE scattering become rapidly more important as the incident energy increases, reflecting the trend of the experimental data. The mass-number dependence of the noncollective excitations is discussed.

Neutron reactions that produce $\alpha$ particles have been investigated experimentally and analyzed by reaction model calculations for incident neutron energies from threshold to 150 MeV on elemental chromium and iron. The cross sections were measured at the Los Alamos Neutron Science Center by direct observation of $\alpha$ particles. Previous data on isotopes ${}^{59}$Co and ${}^{58,60}$Ni were also included in the analysis. The model calculations are made for both statistical decay and pre-equilibrium processes. This study particularly focuses on the pre-equilibrium cluster emission, which is described by the clustering exciton model of Iwamoto and Harada. We calculate the $\alpha$-particle formation factors numerically without any of the approximations that appeared in the original model. The model parameter $\Delta R$, the nuclear surface area where the pickup reaction may occur, is determined by fitting the calculated $\alpha$-particle energy spectra to experimental data. The calculated $\alpha$-particle-production cross sections agree well with the measured data, except for the Cr case. With a simple sensitivity study for the level density parameters, it is reported that relatively small changes in the level density parameters improve the reproduction of experimental data significantly. Our realistic model calculations for the pre-equilibrium process shed light on uncertainties in the nuclear level densities in statistical decay calculation.

The dynamical development of collective flow is studied in a (3+1)-dimensional fluid dynamical model, with globally symmetric, peripheral initial conditions, which take into account the shear flow caused by the forward motion on the projectile side and the backward motion on the target side. While at $\sqrt{s_{NN}}=2.76A$ TeV semiperipheral $\text{Pb}+\text{Pb}$ collisions the earlier predicted rotation effect is visible, at more peripheral collisions, with high resolution and low numerical viscosity, the initial development of a Kelvin-Helmholtz instability is observed, which alters the flow pattern considerably. This effect provides a precision tool for studying the low viscosity of quark-gluon plasma.

Using a (2+1)-dimensional viscous hydrodynamical model, we study the dependence of flow observables on the collision energy ranging from $\sqrt{s}=7.7A$ GeV at the Relativistic Heavy Ion Collider (RHIC) to $\sqrt{s}=2760A$ GeV at the Large Hadron Collider (LHC). With a realistic equation of state, Glauber model initial conditions, and a small specific shear viscosity $\eta /s=0.08$, the differential charged hadron elliptic flow $v_2^{\mathrm{ch}}(p_T,\sqrt{s})$ is found to exhibit a very broad maximum as a function of $\sqrt{s}$ around top RHIC energy, rendering it almost independent of collision energy for $39⩽\sqrt{s}⩽2760A$ GeV. Compared to ideal fluid dynamical simulations, this “saturation” of elliptic flow is shifted to higher collision energies by shear viscous effects. For color-glass-motivated Monte Carlo–Kharzeev-Levin-Nardi initial conditions, which require a larger shear viscosity $\eta /s=0.2$ to reproduce the measured elliptic flow, a similar saturation is not observed up to LHC energies, except for very low $p_T$. We emphasize that this saturation of the elliptic flow is not associated with the QCD phase transition, but arises from the interplay between radial and elliptic flow, which shifts with $\sqrt{s}$ depending on the fluid's viscosity and leads to a subtle cancellation between increasing contributions from light particles and decreasing contributions from heavy particles to $v_2$ in the $\sqrt{s}$ range, where $v_2^{\mathrm{ch}}(p_T,\sqrt{s})$ at fixed $p_T$ is maximal. By generalizing the definition of spatial eccentricity ${\epsilon }_x$ to isothermal hypersurfaces, we calculate ${\epsilon }_x$ on the kinetic freeze-out surface at different collision energies. Up to top RHIC energy, $\sqrt{s}=200A$ GeV, the fireball is still out-of-plane deformed at freeze-out, while at LHC energy the final spatial eccentricity is predicted to approach zero.

We attempt to understand the low-mass dielectron enhancement observed by the PHENIX Collaboration at the Relativistic Heavy Ion Collider by transport peak in the spectral function. On the basis of the second-order formalism of relativistic dissipative hydrodynamics, we parametrize the spectral function in low-frequency and long-wavelength regions by two transport coefficients, electric diffusion coefficient $D$ and relaxation time ${\tau }_{\mathrm{J}}$, and compare our theoretical dielectron spectra with the experimental data. We study the spectrum of dielectrons produced in relativistic heavy-ion collisions by using the profile of matter evolution under full ($3+1$)-dimensional hydrodynamics. We find that the experimental data require the diffusion coefficient to be $D\ge 2/T$, with $T$ being temperature. Our analysis shows that dielectrons emitted through the transport process mainly come from the high-temperature quark-gluon plasma phase.