Negative-parity bands in the vicinity of ${}^{156}\mathrm{Gd}$ and ${}^{160}\mathrm{Yb}$ have been suggested as candidates for the rotation of tetrahedral nuclei. We report the observation of the odd and even-spin members of the lowest energy negative-parity bands in ${}^{160}\mathrm{Yb}$ and ${}^{154}\mathrm{Gd}$. The properties of these bands are similar to the proposed tetrahedral band of ${}^{156}\mathrm{Gd}$ and its even-spin partner. Band-mixing calculations are performed and absolute and relative quadrupole moments deduced for ${}^{160}\mathrm{Yb}$ and ${}^{154}\mathrm{Gd}$. The values are inconsistent with zero, as required for tetrahedral shape, and the bands are interpreted as octupole vibrational bands. The failure to observe the in-band $E2$ transitions of the bands at low spins can be understood using the measured $B(E1)$ and $B(E2)$ values.

Novel simple properties of the monopole component of effective nucleon-nucleon interactions are presented, leading to the so-called monopole-based universal interaction. Shell structures are shown to change as functions of $N$ and $Z$, consistent with experiments. Some key cases of this shell evolution are discussed, clarifying the effects of central and tensor forces. The validity of the present tensor force is examined in terms of the low-momentum interaction $V_{\mathrm{lowk}}$ and the $Q_{\mathrm{box}}$ formalism.

Hydrodynamic simulations are used to make predictions for the integrated elliptic flow coefficient $v_2$ in $\sqrt{s}=5.5\mathrm{TeV}$ lead-lead and $\sqrt{s}=14\mathrm{TeV}$ proton-proton collisions at the LHC. We predict a 10% increase in $v_2$ from RHIC to $\mathrm{Pb}+\mathrm{Pb}$ at LHC, and $v_2\sim 0$ in $p+p$ collisions unless $\eta /s<0.08$.

The third moments of conserved charges, the baryon and electric charge numbers, and energy, as well as their mixed moments, carry more information on the state around the QCD phase boundary than previously proposed fluctuation observables and higher order moments. In particular, their signs give plenty of information on the location of the state created in relativistic heavy ion collisions in the temperature and baryon chemical potential plane. We demonstrate this with an effective model.

The cross sections for single-neutron removal from the very neutron-rich nucleus ${}^{31}\mathrm{Ne}$ on Pb and C targets have been measured at $230\mathrm{MeV}/\mathrm{\text{nucleon}}$ using the RIBF facility at RIKEN. The deduced large Coulomb breakup cross section of 540(70) mb is indicative of a soft $E1$ excitation. Comparison with direct-breakup model calculations suggests that the valence neutron of ${}^{31}\mathrm{Ne}$ occupies a low-$\ell$ orbital (most probably $2p_{3/2}$) with a small separation energy ($S_n\lesssim 0.8\mathrm{MeV}$), instead of being predominantly in the $1f_{7/2}$ orbital as expected from the conventional shell ordering. These findings suggest that ${}^{31}\mathrm{Ne}$ is the heaviest halo system known.

The superallowed $\beta$-decay $Q_{\mathrm{EC}}$ values of ${}^{34}\mathrm{Cl}$ and ${}^{38}\mathrm{K}^m$ have been measured with an online Penning trap to be 5491.662(47) keV and 6044.223(41) keV, respectively. The new values are more precise than the previous high-precision reaction-based values but are consistent with them and establish that there are no significant systematic differences between the two types of measurements.

Experimental studies of one-nucleon knockout from magic nuclei suggest that their nucleon orbits are not fully occupied. This conflicts a commonly accepted view of the shell closure associated with such nuclei. The conflict can be reconciled if the overlap between initial and final nuclear states in a knockout reaction are calculated by a nonstandard method. The method employs an inhomogeneous equation based on correlation-dependent effective nucleon-nucleon interactions and allows the simplest wave functions, in which all nucleons occupy only the lowest nuclear orbits, to be used. The method also reproduces the recently established relation between reduction of spectroscopic strength, observed in knockout reactions on other nuclei, and nucleon binding energies. The implication of the inhomogeneous equation method for the physical meaning of spectroscopic factors is discussed.

The effects of fluctuating initial conditions are studied in the context of relativistic heavy ion collisions where a rapidly evolving system is formed. Two-particle correlation analysis is applied to events generated with the NEXSPHERIO hydrodynamic code, starting with fluctuating nonsmooth initial conditions (IC). The results show that the nonsmoothness in the IC survives the hydroevolution and can be seen as topological features of the angular correlation function of the particles emerging from the evolving system. A long range correlation is observed in the longitudinal direction and in the azimuthal direction a double peak structure is observed in the opposite direction to the trigger particle. This analysis provides clear evidence that these are signatures of the combined effect of tubular structures present in the IC and the proceeding collective dynamics of the hot and dense medium.

Results of measurement of residues formed in fusion of ${}^6\mathrm{Li}$ with ${}^{198}\mathrm{Pt}$ in the energy range of $0.68<E/V_b<1.3$ using a new sensitive off-beam technique are reported. The fusion excitation function and the derived average angular momenta do not indicate a change of slope at deep sub-barrier energies, contrary to recent observations. The present results for a system with weakly bound projectile confront the current understanding of the fusion hindrance at these low energies, underlying the role of internal reorganization on the dynamical path towards fusion.

A modern variation of the Rutherford experiment to probe the tunneling of exotic nuclear matter from the measurement of the residues formed in the bombardment of ${}^{197}\mathrm{Au}$ by extremely neutron-rich ${}^8\mathrm{He}$ nuclei is presented. Using a novel off-beam technique the most precise and accurate measurements of fusion and neutron transfer involving reaccelerated unstable beams are reported. The results show unusual behavior of the tunneling of ${}^8\mathrm{He}$ compared to that for lighter helium isotopes, highlighting the role of the intrinsic structure of composite many-body quantum systems and pairing correlations.

To determine which nuclei may exhibit shape isomerism, we use a well-benchmarked macroscopic-microscopic model to calculate potential-energy surfaces as functions of spheroidal (${ϵ}_2$), hexadecapole (${ϵ}_4$), and axial-asymmetry ($\gamma$) shape coordinates for 7206 nuclei from $A=31$ to $A=290$. We analyze these and identify the deformations and energies of all minima deeper than 0.2 MeV. These minima may correspond to characteristic experimentally observable shape-isomeric states. Shape isomers mainly occur in the $A=80$ region, the $A=100$ region, and in an extended region centered around ${}^{208}\mathrm{Pb}$. We compare our model to experimental results for Kr isotopes. Moreover, in a plot versus $N$ and $Z$ we show for each of the 7206 nuclei the calculated number of minima. The results reveal one fairly unexplored region of shape isomerism, which is experimentally accessible, namely the region northeast of ${}_{82}{}^{208}\mathrm{Pb}$.

New Jefferson Lab data are presented on the nuclear dependence of the inclusive cross section from ${}^2\mathrm{H}$, ${}^3\mathrm{He}$, ${}^4\mathrm{He}$, ${}^9\mathrm{Be}$ and ${}^{12}\mathrm{C}$ for $0.3<x<0.9$, $Q^2\approx 3–6{\mathrm{GeV}}^2$. These data represent the first measurement of the EMC effect for ${}^3\mathrm{He}$ at large $x$ and a significant improvement for ${}^4\mathrm{He}$. The data do not support previous $A$-dependent or density-dependent fits to the EMC effect and suggest that the nuclear dependence of the quark distributions may depend on the local nuclear environment.

We propose a novel extension of the standard coupled-channels framework for heavy-ion reactions in order to analyze fusion reactions at deep-sub-barrier incident energies. This extension simulates a smooth transition between the two-body and the adiabatic one-body states. To this end, we damp gradually the off-diagonal part of the coupling potential, for which the position of the onset of the damping varies for each eigenchannel. We show that this model accounts well for the steep falloff of the fusion cross sections for the ${}^{16}\mathrm{O}+{}^{208}\mathrm{Pb}$, ${}^{64}\mathrm{Ni}+{}^{64}\mathrm{Ni}$, and ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$ reactions.

An experimental study of the ${}^{16}\mathrm{O}(e,e^{\prime }{K}^{+}){}_{\Lambda }{}^{16}\mathrm{N}$ reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the $p(e,e^{\prime }{K}^{+})\Lambda ,{\Sigma }^0$ exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of $13.76\pm 0.16\mathrm{MeV}$ was obtained for ${}_{\Lambda }{}^{16}\mathrm{N}$ with better precision than previous measurements on the mirror hypernucleus ${}_{\Lambda }{}^{16}\mathrm{O}$. Precise energies have been determined for peaks arising from a $\Lambda$ in $s$ and $p$ orbits coupled to the $p_{1/2}$ and $p_{3/2}$ hole states of the ${}^{15}\mathrm{N}$ core nucleus.

We consider the proton and neutron quasiparticle orbits around the closed-shell ${}^{56}\mathrm{Ni}$ and ${}^{48}\mathrm{Ca}$ isotopes. It is found that large model spaces (beyond the capability of shell model applications) are necessary for predicting the quenching of spectroscopic factors. The particle-vibration coupling is identified as the principal mechanism. Additional correlations—due to configuration with several particle-hole excitations—are estimated using shell model calculations and generate an extra reduction which is $\lesssim 4\%$ for most quasiparticle states. The theoretical calculations nicely agree with ($e$, $e^{\prime }p$) and inverse kinematics knockout experiments. These results open a new path for a microscopic understanding of the shell model.

In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in ${}^{10}\mathrm{Be}$ using the Doppler shift attenuation method (DSAM) following the ${}^7\mathrm{Li}({}^7\mathrm{Li},\alpha ){}^{10}\mathrm{Be}$ reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The $J^{\pi }=2_1^{+}$ state at 3.37 MeV has $\tau =205\pm (5{)}_{\mathrm{stat}}\pm (7{)}_{\mathrm{sys}}\mathrm{fs}$ corresponding to a $B(E2\downarrow )$ of $9.2(3)e^2{\mathrm{fm}}^4$ in broad agreement with many calculations. The $J^{\pi }=2_2^{+}$ state at 5.96 MeV was found to have a $B(E2\downarrow )$ of $0.11(2)e^2{\mathrm{fm}}^4$ and provides a more discriminating test of nuclear models. New Green’s function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

We have measured the branching ratio of the three-body process in the nonmesonic weak decay of ${}_{\Lambda }{}^{12}\mathrm{C}$ to be $0.29\pm 0.13$. This result was obtained by reproducing the nucleon and the nucleon pair yields introducing a measured final state interaction. At the same time, we have determined the absolute decay widths, ${\Gamma }_n$ and ${\Gamma }_p$, along with ${\Gamma }_{2N}$, whose relative ratio has been a long-standing puzzle. Including the three-body process, we have successfully reproduced the nucleon energy distribution, the coincidence two-nucleon angular correlation, and the momentum sum distribution simultaneously.

We perform ab initio calculations for nuclei around ${}^{16}\mathrm{O}$, ${}^{40}\mathrm{Ca}$, and ${}^{56}\mathrm{Ni}$ using realistic nucleon-nucleon forces. In particular, ${}^{56}\mathrm{Ni}$ is computed as the heaviest nucleus in this kind of ab initio calculation. Ground-state and single-particle energies including three-body-cluster effects are obtained within the framework of the unitary-model-operator approach. It is shown that the CD-Bonn nucleon-nucleon potential gives quite good results close to the experimental values for all nuclei in the present work.

A hadron resonance gas model including all known particles and resonances with masses $m<2\mathrm{GeV}$ and an exponentially rising density of Hagedorn states for $m>2\mathrm{GeV}$ is used to obtain an upper bound on the shear viscosity to entropy density ratio, $\eta /s\approx 1/(4\pi )$, of hadronic matter near $T_c$. We found a large trace anomaly and small speed of sound near $T_c$, which agree well with recent lattice calculations. We comment on the bulk viscosity to entropy density ratio close to $T_c$.

Experiments at the Relativistic Heavy Ion Collider (RHIC) suggest that the state of matter produced in the experiments has a low shear-viscosity to entropy-density ratio $\eta /s$. We ask here the following question: what is this ratio in the usual finite nuclei at low temperature? We use the experimental and theoretical results for the widths of giant vibrational states in nuclei in order to calculate the above ratio. We find that the values of $\eta /s$ are not very different from the ones found in the RHIC experiments.