Nucleus-nucleus potentials are determined in the framework of the double-folding model for a new microscopic nucleon-nucleon (NN) interaction relativistic mean field-3-Yukawa (R3Y) derived from the popular relativistic mean-field theory Lagrangian, and the results are compared for the use of Michigan-3-Yukawa (M3Y) effective NN interactions. The double-folding potentials so obtained are further taken up in the context of the preformed cluster model (PCM) of Gupta and collaborators and the barrier penetration model to study respectively the ground-state (g.s.) $\alpha$-decay and low-energy fusion reactions. In this paper, using PCM, we deduce empirically the $\alpha$ preformation probability ${P_0}^{\alpha (\text{emp})}$ from experimental data on a few g.s. $\alpha$ decays in the trans-lead region. For fusion reactions, two projectile-target systems ${}^{12}\mathrm{C}$$+$${}^{208}\mathrm{Pb}$ and ${}^{16}\mathrm{O}$$+$${}^{208}\mathrm{Pb}$ are selected for calculating the barrier energies as well positions, fusion cross sections (${\sigma }_{\text{fus}}$), and fusion barrier distribution [$D(E_{\text{c.m.}}$)]. The barrier energies and positions change for the R3Y NN interactions in comparison with those of the M3Y NN interactions. We find that in the $\alpha$-decay studies the values of ${P_0}^{\alpha (\text{emp})}$(R3Y) are similar to those of ${P_0}^{\alpha (\text{emp})}$(M3Y). Further, both NN interactions give similar ${\sigma }_{\text{fus}}$ values using the Wong formula specifically when the R3Y NN interaction calculated ${\sigma }_{\text{fus}}$ values are reduced by 1.5 times, and the results are in agreement with the experimental data for both the systems, especially for the higher energies. Results for $D(E_{\text{c.m.}}$) are also quite similar for both choices of NN interaction.

The reaction ${}^{17}\mathrm{O}$$(\alpha ,\gamma ){}^{21}$Ne has been measured by in-beam $\gamma$ spectroscopy for the first time in the energy range $E_{\alpha }=750$–1650 keV using highly enriched anodized ${\text{Ta}}_2({}^{17}\text{O}){}_5$ targets. Resonances were found at $E_{\alpha }=$ 1002, 1386, and 1619 keV. Their strengths and primary $\gamma$-ray branchings are given. The new results exclude the low reaction rate of Descouvemont and support the rate of Caughlan and Fowler. Implications for the neutron poisoning efficiency of ${}^{16}\mathrm{O}$ in the weak $s$-process are discussed.

Measurements and reaction model calculations are reported for single-neutron pickup reactions onto a fast ${}^{22}\mathrm{Mg}$ secondary beam at 84 MeV per nucleon. Measurements made on both carbon and beryllium targets, having very different structures, were used to investigate the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and $\gamma$-ray spectroscopy of the projectile-like reaction residue for final-state resolution, which permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the ${}^{12}\mathrm{C}({}^{22}\mathrm{Mg},{}^{23}\mathrm{Mg}+\gamma )X$ reaction largely proceeds as a direct two-body reaction, with the neutron transfer producing bound ${}^{11}\mathrm{C}$ target residues. The corresponding reaction on the ${}^9\mathrm{Be}$ target seems to largely leave the ${}^8\mathrm{Be}$ residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei and also their expected sensitivity to neutron high-$\ell$ (intruder) states, which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.

Decay modes of excited nuclei are investigated in ${}^{78,82}\mathrm{Kr}$$+$${}^{40}\mathrm{Ca}$ reactions at 5.5 MeV/nucleon. Charged products were measured by means of the $4\pi$ INDRA array. Kinetic-energy spectra and angular distributions of fragments with atomic number 3 $⩽Z⩽$ 28 indicate a high degree of relaxation and are compatible with a fissionlike phenomenon. Persistence of structure effects is evidenced from elemental cross sections (${\sigma }_Z$) as well as a strong odd-even staggering (o-e-s) of the light-fragment yields. The magnitude of the staggering does not significantly depend on the neutron content of the emitting system. Fragment-particle coincidences suggest that the light partners in very asymmetric fission are emitted either cold or at excitation energies below the particle emission thresholds. The evaporation residue cross section of the ${}^{78}\mathrm{Kr}$$+$${}^{40}\mathrm{Ca}$ reaction is slightly higher than the one measured in the ${}^{82}\mathrm{Kr}$$+$${}^{40}\mathrm{Ca}$ reaction. The fissionlike component is larger by $~$25% for the reaction having the lowest neutron-to-proton ratio. These experimental features are confronted to the predictions of theoretical models. The Hauser-Feshbach approach including the emission of fragments up to $Z$ $=$ 14 in their ground states as well as excited states does not account for the main features of ${\sigma }_Z$. For both reactions, the transition-state formalism reasonably reproduces the $Z$ distribution of the fragments with charge 12 $⩽Z⩽$ 28. However, this model strongly overestimates the light-fragment cross sections and does not explain the o-e-s of the yields for 6 $⩽Z⩽$ 10. The shape of the whole $Z$ distribution and the o-e-s of the light-fragment yields are satisfactorily reproduced within the dinuclear system framework which treats the competition among evaporation, fusion-fission, and quasifission processes. The model suggests that heavy fragments come mainly from quasifission while light fragments are predominantly populated by fusion. An underestimation of the cross sections for 16 $⩽Z⩽$ 22 could signal a mechanism in addition to the capture process.

The fusion hindrance in heavy-ion collisions is studied in the framework of the two-center liquid drop model. It appears that the neck and the radial degrees of freedom might both be hampered by an inner potential barrier on their path between the contact configuration to the compound nucleus. Heavy-ion reactions with and without the two kinds of fusion hindrance are classified through systematic calculations. It is found that the number of reactions without radial fusion hindrance is much smaller than that without neck fusion hindrance, and for both kinds of fusion hindrance the number of reactions without fusion hindrance at small mass-asymmetry parameter $\alpha$ is smaller than that at large $\alpha$. In the formation of a given compound nucleus, if a reaction with ${\alpha }_c$ is not hindered, then other reactions with $\alpha >{\alpha }_c$ are also not hindered, as is well known experimentally.

A variety of physical phenomena have at their foundation the quantum tunneling of particles through potential barriers. Many of these phenomena can be associated with the tunneling of single inert particles. The tunneling of composite systems is more complex than for single particles due to the coupling of the tunneling coordinate with the internal degrees of freedom of the tunneling system. Reported here are the results of a study for the tunneling of a two-component projectile incident on a potential energy system which differs for the two components. A specific linkage is made to sub-Coulomb nuclear reactions.

Recent fusion reaction data for the systems ${}^{36}\mathrm{S}+{}^{48}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, and ${}^{96}\mathrm{Zr}+{}^{48}\mathrm{Ca}$ are analyzed within the coupled-channel formalism. The heavy-ion entrance channel potential is calculated employing an improved double-folding prescription. The nonlocal kernel arising from the knock-on exchange component of the effective $N-N$ interaction is localized within the lowest order of the Perey-Saxon approach, including full recoil. The single-particle densities entering the folding integrals are prescribed according to the density matrix expansion method. The investigation is more elaborated because each case is tested with four different types of $N-N$ effective forces: The two standard parametrizations of the density-independent M3Y force (Reid and Paris) and two parametrizations of the density-dependent Gogny force (D1S and D1N). A consistent description of all three reactions is achieved by keeping fixed the nuclear structure input for ${}^{48}\mathrm{Ca}$. The inclusion of 2${}^{+}$ and 3${}^{-}$ phonon states in the coupled-channel calculation, within an energy excitation window identical for all three reactions explains better the hindrance in extreme sub-barrier fusion cross sections. The interactions providing the best fit to the data are not pointing to a possible maximum in the astrophysical $S$ factor, thereby confirming the conclusion reached by the Legnaro group for these cases.

Recently, a new measurement of the ${}^6\mathrm{Li}$ (150 A MeV)dissociation in the field of ${}^{208}\mathrm{Pb}$ has been reported [Hammache et al., Phys. Rev. C 82, 065803 (2010)] to study the radiative capture $\alpha +d\to {}^6\mathrm{Li}+\gamma$ process. However, the dominance of the nuclear breakup over the Coulomb one prevented the information about the $\alpha +d\to {}^6\mathrm{Li}+\gamma$ process from being obtained from the breakup data. The astrophysical $S_{24}(E)$ factor has been calculated within the $\alpha -d$ two-body potential model with potentials determined from the fits to the $\alpha -d$ elastic scattering phase shifts. However, the scattering phase shift, according to the theorem of the inverse scattering problem, does not provide a unique $\alpha -d$ bound-state potential, which is the most crucial input when calculating the $S_{24}(E)$ astrophysical factor at astrophysical energies. In this work, we emphasize the important role of the asymptotic normalization coefficient (ANC) for ${}^6\mathrm{Li}\to \alpha +d$, which controls the overall normalization of the peripheral $\alpha +d\to {}^6\mathrm{Li}+\gamma$ process and is determined by the adopted $\alpha -d$ bound-state potential. Since the potential determined from the elastic scattering data fit is not unique, the same is true for the ANC generated by the adopted potential. However, a unique ANC can be found directly from the elastic scattering phase shift, without invoking intermediate potential, by extrapolation the scattering phase shift to the bound-state pole [Blokhintsev et al., Phys. Rev. C 48, 2390 (1993)]. We demonstrate that the ANC previously determined from the $\alpha -d$ elastic scattering $s$-wave phase shift [Blokhintsev et al., Phys. Rev. C 48, 2390 (1993)], confirmed by ab initio calculations, gives $S_{24}(E)$, which at low energies is about $38\%$ less than the other one reported [Hammache et al., Phys. Rev. C 82, 065803 (2010)]. We recalculate also the reaction rates, which are lower than those obtained in that same study [Hammache et al., Phys. Rev. C 82, 065803 (2010)].

Neutron-unbound resonant states of ${}^{11}\mathrm{Be}$ were populated in neutron knockout reactions from ${}^{12}\mathrm{Be}$ and identified by ${}^{10}\mathrm{Be}$–$n$ coincidence measurements. A resonance in the decay-energy spectrum at 80(2) keV was attributed to a highly excited unbound state in ${}^{11}\mathrm{Be}$ at 3.949(2) MeV decaying to the $2^{+}$ excited state in ${}^{10}\mathrm{Be}$. A knockout cross section of 15(3) mb was inferred for this 3.949(2) MeV state, suggesting a spectroscopic factor near unity for this $0p3/2^{-}$ level, consistent with the detailed shell model calculations.

The ground-state energy of infinite symmetric nuclear matter is usually described by strongly interacting nucleons obeying the Pauli exclusion principle. We can imagine a unitary transformation which groups four nonidentical nucleons (i.e., with different spin and isospin) close in coordinate space. Those nucleons, being nonidentical, do not obey the Pauli principle, thus their relative momenta are negligibly small (just to fulfill the Heisenberg principle). Such a cluster can be identified with an $\alpha$ boson. But in dense nuclear matter, those $\alpha$ particles still obey the Pauli principle since are constituted of fermions. The ground state energy of nuclear matter $\alpha$ clusters is the same as for nucleons, thus it is degenerate. We could think of $\alpha$ particles as vortices which can now braid, for instance making ${}^8\mathrm{Be}$ which leave the ground state energy unchanged. Further braiding to heavier clusters (${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$$,\dots$) could give a different representation of the ground state at no energy cost. In contrast $d$-like clusters (i.e., $N=Z$ odd-odd nuclei, where $N$ and $Z$ are the neutron and proton number, respectively) cannot describe the ground state of nuclear matter and can be formed at high excitation energies (or temperatures) only. We show that even-even, $N=Z$, clusters could be classified as non-Abelian states of matter. As a consequence an $\alpha$ condensate in nuclear matter might be hindered by the Fermi motion, while it could be possible a condensate of ${}^8\mathrm{Be}$ or heavier clusters.

Microscopic calculations based on realistic nuclear Hamiltonians, while yielding accurate results for the energies of the ground and low-lying excited states of nuclei with $A⩽12$, fail to reproduce the empirical equilibrium properties of nuclear matter, that are known to be significantly affected by three-nucleon forces. We discuss a scheme suitable to construct a density-dependent two-nucleon potential, in which the effects of $n$-particle interactions can be included by integrating out the degrees of freedom of $(n-2)$ nucleons. Our approach, based on the formalism of correlated basis function and state-of-the-art models of the two- and three-nucleon potentials, leads to an effective interaction that can be easily employed in nuclear matter calculations, yielding results in good agreement with those obtained from the underlying three-body potential.

A recently developed three-dimensional approach (without partial-wave decomposition) is considered to investigate solutions of Faddeev-Yakubovsky integral equations in momentum space for three- and four-body bound states, with the inclusion of three-body forces. In the calculations of the binding energies, spin-dependent nucleon-nucleon ($\mathit{NN}$) potential models [soft-core potential S3, Malfliet-Tjon (MT) I-III, Yamaguchi-type potentials (YS), and $P_{5.5}$-model of Gibson-Lehman (P${}_{55}$GL)] are considered along with the scalar two-meson exchange three-body potential. The presently reported results agree well with the ones obtained by other techniques, demonstrating the advantage of an approach in which the formalism is much more simplified and easy to manage for direct computation.

We discuss the convergence of the expansion of the nuclear electroweak current in powers of $\left|\mathbf{k}\right|/M$, where $M$ is the nucleon mass and $\mathbf{k}$ denotes either the momentum transfer or the momentum of the struck nucleon. We have computed the electron and neutrino scattering cross sections off uniform nuclear matter at equilibrium density using correlated wave functions and the cluster expansion formalism. The results of our work suggest that the proposed approach provides accurate estimates of the measured electron scattering cross sections. On the other hand, the description of the current based on the widely used leading-order approximation does not appear to be adequate, even at momentum transfer as low as 300 MeV.

The continuum-discretized coupled-channels method (CDCC) for exclusive reactions and the eikonal reaction theory (ERT) as an extension of CDCC to inclusive reactions are applied to deuteron-induced reactions. The CDCC result reproduces experimental data on the reaction cross section for $d+{}^{58}$Ni scattering at 200 MeV/nucleon, and ERT provides data on the neutron-stripping cross section for inclusive ${}^7\mathrm{Li}$$(d,n)$ reaction at 40 MeV. For deuteron-induced reactions at 200 MeV/nucleon, target-dependence of the reaction, elastic-breakup, nucleon-stripping, nucleon-removal, and complete- and incomplete-fusion cross sections is clearly explained by simple formulas. Accuracy of the Glauber model is also investigated.

Experiments with the new recoil separator, Transactinide Separator and Chemistry Apparatus (TASCA), at the GSI were performed by using beams of ${}^{48}\mathrm{Ca}$ to irradiate targets of ${}^{206-208}\mathrm{Pb}$, which led to the production of ${}^{252-254}\mathrm{No}$ isotopes. These studies allowed for evaluation of the performance of TASCA when coupled to a new detector and electronics system. By following these studies, the isotopes of element 114 (${}^{288-291}$114) were produced in irradiations of ${}^{244}\mathrm{Pu}$ targets with ${}^{48}\mathrm{Ca}$ beams at compound nucleus excitation energies around 41.7 and 37.5 MeV, demonstrating TASCA's ability to perform experiments with picobarn-level cross sections. A total of 15 decay chains were observed and were assigned to the decay of ${}^{288-291}$114. A new α-decay branch in ${}^{281}\mathrm{Ds}$ was observed, leading to the new nucleus ${}^{277}\mathrm{Hs}$.

Using the newly developed hybrid model VISHNU, which connects viscous hydrodynamics with a hadron cascade model, we study the differential and integrated elliptic flow $v_2$ at different centrality bins for 200 A GeV Au$+$Au collisions and $2.76$ A TeV Pb$+$Pb collisions. We find that the average quark-gluon plasma (QGP)-specific shear viscosity $\eta /s$ slightly increases from Relativistic Heavy Ion Collider to Large Hadron Collider (LHC) energies. However, a further study assuming different temperature dependencies for $(\eta /s){}_{\mathrm{QGP}}$ shows that one cannot uniquely constrain the form of $(\eta /s){}_{\mathrm{QGP}}(T)$ by fitting the spectra and $v_2$ alone. Based on our current understanding, the question whether the QGP fluid is more viscous or more perfect in the temperature regime reached by LHC energies is still open.

The distribution of the two-phonon $\gamma$-vibrational collectivity in the rotating triaxial odd-$A$ nucleus ${}^{103}\mathrm{Nb}$, which is one of the three nuclides for which experimental data were reported recently, is calculated in the framework of the particle vibration coupling model based on the cranked shell model plus random phase approximation. This framework was previously utilized for analyses of the zero- and one-phonon bands in another mass region and is applied to the two-phonon band for the first time. In the present calculation, three sequences of two-phonon bands share collectivity almost equally at finite rotation whereas the $K=\Omega +4$ state is the purest at zero rotation.

The ${\Delta }_3(L)$ statistic of random matrix theory is defined as the average of a set of random numbers $\{\delta \}$, derived from a spectrum. The distribution $p(\delta )$ of these random numbers is used as the basis of a maximum likelihood method to gauge the fraction $x$ of levels missed in an experimental spectrum. The method is tested on an ensemble of depleted spectra from the Gaussian orthogonal ensemble (GOE) and accurately returned the correct fraction of missed levels. Neutron resonance data and acoustic spectra of an aluminum block were analyzed. All results were compared with an analysis based on an established expression for ${\Delta }_3(L)$ for a depleted GOE spectrum. The effects of intruder levels are examined and seen to be very similar to those of missed levels. Shell model spectra were seen to give the same $p(\delta )$ as the GOE.

A sensitive search of the 4-fold forbidden nonunique decay of ${}^{50}\mathrm{V}$ has been performed. A total mass measuring time product of 186 kg d has been accumulated. A reliable half-life value with the highest precision so far of $(2.29\pm 0.25)\times {10}^{17}$ years of the electron capture decay of ${}^{50}\mathrm{V}$ into the first excited state of ${}^{50}\mathrm{Ti}$ could be obtained. A photon emission line following the $\beta$ decay into the first excited state of ${}^{50}\mathrm{Cr}$ could not be observed, resulting in a lower limit on the half-life of the $\beta$-decay branch of $1.7\times {10}^{18}$ years. This is not in good agreement with a claimed observation of this decay branch published in 1989.

Excited states in the stable nucleus ${}^{193}\mathrm{Ir}$ have been investigated through an in-beam $\gamma$-ray spectroscopic technique following the ${}^{192}\mathrm{Os}$(${}^7\mathrm{Li}$, $\alpha 2n$) reaction at a beam energy of 44 MeV. A level scheme built on the $\pi h_{11/2}$ isomer has been extended to high-spin states using eleven newly observed $\gamma$ transitions. The $\pi h_{11/2}$ band is proposed to be formed by coupling an $h_{11/2}$ proton to a core with large triaxial deformation. Three-quasiparticle states are suggested in ${}^{193}\mathrm{Ir}$ on referring to the similar states in ${}^{187}\mathrm{Ir}$. The features of signature splitting in the $\pi h_{11/2}$ bands of ${}^{187-193}$Ir are discussed with the help of total Routhian surface calculations.