The standard $\gamma$-ray energy calibration source ${}^{152}\mathrm{Eu}$ is well known based on the 13.5 y decay of its ground state. However, in addition to this decay ${}^{152}\mathrm{Eu}$ also has two relatively long-lived isomeric states: a 9 h $J^{\pi }=0^{-}$ state at $E^{*}=46$ keV and a 96 min $J^{\pi }=8^{-}$ state at $E^{*}=148$ keV. Here we report a new measurement of the half-lives of both of these isomeric states. Excited states in ${}^{152}\mathrm{Eu}$ were populated following the ${}^{154}\mathrm{Sm}\left(p,3n\right)$ reaction using a 25 MeV proton beam from the K-150 cyclotron at the Cyclotron Institute of Texas A&M University. Post irradiation, $\gamma$ rays from the de-excitation of the long lived isomeric states were measured using the six BGO shielded high-purity germanium (HPGe) clover detectors that are part of the STARLiTeR array. The half-life of the $J^{\pi }=8^{-}$ isomer ${}^{152m_2}\mathrm{Eu}$ was obtained by measuring the decrease in intensity of the 90 keV $\gamma$ ray from the cascade to the ground state. The half-life of this state was measured to be 95.8(4) min which is in agreement with and significantly more precise than the previously measured value of 96(1) min. In a manner similar to the ground state the second long-lived isomer ${}^{151m_1}\mathrm{Eu}$, the $J^{\pi }=0^{-}$ state at 46 keV, $\beta$ decays to excited states in ${}^{152}\mathrm{Gd}$ and ${}^{152}\mathrm{Sm}$. The half-life of this state was measured to be 9.39(7) h using five $\gamma$-ray transitions.

We investigate the energy of vanishing flow (EVF) as a function of colliding geometry for various reactions and confront our theoretical calculations with available experimental data. Our findings using an isospin-dependent quantum molecular dynamics (IQMD) model reveal that measured energies of vanishing flow can be reproduced nicely by IQMD model calculations. We also analyze, in detail, the role of hard and soft equations of state (with and without momentum-dependent interactions) in transverse flow and its disappearance over a wide range of mass and impact parameters. Our investigations reveal that the mass dependence of the energy of vanishing flow at peripheral collisions can act as a useful probe to pin down the stiffness of nuclear matter.

Background: It was shown recently that an anomaly in the elastic scattering of ${}^{16}\mathrm{O}$ on ${}^{12}\mathrm{C}$ at around 300 MeV is resolved by including within the scattering model the inelastic excitation of specific collective excitations of both nuclei, leading to a secondary rainbow. There is very little systematic knowledge concerning the contribution of collective excitations to the interaction between nuclei, particularly in the overlap region when neither interacting nuclei are light nuclei.

Purpose: Our goals are to study the dynamic polarization potential (DPP) generated by channel coupling that has been experimentally validated for a case (${}^{16}\mathrm{O}$ on ${}^{12}\mathrm{C}$ at around 300 MeV) where scattering is sensitive to the nuclear potential over a wide radial range; to exhibit evidence of the nonlocality due to collective coupling; to validate, or otherwise invalidate, the representation of the DPP by uniform renormalizing folding models or global potentials.

Methods: $S$-matrix to potential, $S_L\to V\left(r\right)$, inversion yields local potentials that reproduce the elastic channel $S$ matrix of coupled channel calculations. Subtracting the elastic channel uncoupled potential yields a local $L$-independent representation of the DPP. The dependence of the DPP on the nature of the coupled states and other parameters can be studied.

Results: Local DPPs were found due to the excitation of ${}^{12}\mathrm{C}$ and the combined excitation of ${}^{16}\mathrm{O}$ and ${}^{12}\mathrm{C}$. The radial forms were different for the two cases, but each were very different from a uniform renormalization of the potential. The full coupling led to a 10% increase in the volume integral of the real potential. Evidence for the nonlocality of the underlying formal DPP and for the effect of direct coupling between the collective states is presented.

Conclusions: The local DPP generating the secondary rainbow has been identified. In general, DPPs have forms that depend on the nature of the specific excitations generating them, but, as in this case, they cannot be represented by a uniform renormalization of a global model or folding model potential. The method employed herein is a useful tool for further exploration of the contribution of collective excitations to internuclear potentials, concerning which there is still remarkably little general information.

Dynamical charge fluctuations have been studied in ultrarelativistic heavy-ion collisions by using hadronic model simulations, such as Ultrarelativistic Quantum Molecular Dynamics (UrQMD) and Heavy Ion Jet Interaction Generator (HIJING). The evolution of fluctuations has been calculated at different time steps during the collision as well as at different observation windows in pseudorapidity $(△\eta )$. The final state effects on the fluctuations have been investigated by varying $△\eta$ and the time steps with the aim of obtaining an optimum observation window for capturing maximum fluctuations. It is found that $△\eta$ between 2.0 and 3.5 gives the best coverage for the fluctuations studies. The results of these model calculations for $\text{Au}+\text{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7 to 200 GeV and for $\text{Pb}+\text{Pb}$ collisions at 2.76 TeV are presented and compared to the available experimental data from the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).

It has been debated for decades whether hadrons emerging from $p+p$ collisions exhibit collective expansion. The signal of the collective motion in $p+p$ collisions is not as clear or as clean as in heavy-ion collisions because of the low multiplicity and large fluctuation in $p+p$ collisions. The Tsallis blast-wave (TBW) model is a thermodynamic approach, introduced to handle the overwhelming correlation and fluctuation in the hadronic processes. We have systematically studied the identified particle spectra in $p+p$ collisions from the BNL Relativistic Heavy Ion Collider (RHIC) to the CERN Large Hadron Collider (LHC) using TBW and have found no appreciable radial flow in $p+p$ collisions below $\sqrt{s}=900$ GeV. At the LHC higher energy of 7 TeV in $p+p$ collisions, the radial flow velocity achieves an average value of $\langle \beta \rangle =0.320\pm 0.005$. This flow velocity is comparable to that in peripheral (40–60%) $\mathrm{Au}+\mathrm{Au}$ collisions at the RHIC. Breaking of the identified particle spectra $m_T$ scaling was also observed at the LHC from a model-independent test.

A colorless $\overline{c}c$ dipole emerging from a heavy ion collision and developing the charmonium wave function can be broken up by final state interactions (FSI) propagating through the hot medium created in the collision. We single out two mechanisms of charmonium attenuation: (i) Debye color screening, called melting; and (ii) color-exchange interaction with the medium, called absorption. The former problem was treated so far only for charmonia at rest embedded in the medium, while in practice their transverse momenta at the LHC are quite high, $\langle p_T^2\rangle =7$–10 ${\mathrm{GeV}}^2$. We demonstrate that a $\overline{c}c$ dipole may have a large survival probability even at infinitely high temperature. We develop a procedure of Lorentz boosting of the Schrödinger equation to a moving reference frame and perform the first realistic calculations of the charmonium survival probability employing the path-integral technique, incorporating both melting and absorption. These effects are found to have comparable magnitudes. We also calculated the FSI suppression factor for the radial excitation $\psi \left(2S\right)$ and found it to be stronger than for $J/\psi$, except large $p_T$, where $\psi \left(2S\right)$ is relatively enhanced. The azimuthal asymmetry parameter $v_2$ is also calculated.

Properties of the experimentally inaccessible $N=82$ isotones below ${}^{132}\mathrm{Sn}$ have been a major open question for nuclear structure and nuclear astrophysics. Evolution of the neutron $N=82$ shell gap along this isotonic chain with even proton numbers $36–48$ is investigated by large-scale shell model calculations, which allow core excitations across both the $N=82$ neutron and $Z=50$ proton shell gaps. It is found that when moving away from ${}^{132}\mathrm{Sn},$ the $N=82$ shell gap, measured by the excited $2^{+}$ states with the neutron core-excited configurations, decreases gradually due to the monopole interaction acting dynamically between the $\pi g_{9/2}$ and $\nu h_{11/2}$ orbits. At ${}^{120}\mathrm{Sr},$ the neutron core-excited configuration is sufficiently low and becomes the dominant component in the first excited $2^{+}$ state, which results in a quenching of the $Z=40$ subshell. Measurement of $E2$ transition probabilities in ${}^{120}\mathrm{Sr}$ is proposed to confirm this novel shell-quenching mechanism.

High-spin states in ${}^{139}\mathrm{Ce}$ have been populated using the ${}^{130}\mathrm{Te}({}^{14}\mathrm{C},5n)$ reaction. The level scheme has been extended to higher spins, including a new band of dipole transitions. The parity of several states has been changed from negative to positive, mainly based on the comparison with the level structure of the core nucleus ${}^{140}\mathrm{Ce}$ and the results of a realistic shell-model calculation. The dipole band is interpreted as a magnetic rotation band with $\pi h_{11/2}^2\otimes \nu h_{11/2}^{-1}$ configuration built on small deformation axial shape with $({\varepsilon }_2=0.12,\gamma =0^{\circ })$.

High spin states in ${}^{105}\mathrm{Cd}$ were studied using ${}^{92}\mathrm{Mo}\left({}^{16}\mathrm{O},2pn\right){}^{105}\mathrm{Cd}$ reaction at an incident beam energy of 75 MeV. The level scheme of ${}^{105}\mathrm{Cd}$ has been observed up to $J^{\pi }=\left(47/2^{-}\right)$ and excitation energy $\sim 10.8\mathrm{MeV}$ with the addition of 30 new $\gamma$ transitions to the previous work. Spin and parity for most of the reported levels are assigned from the directional correlation orientation (DCO) ratios and linear polarization measurements. The microscopic origin of the investigated band structures is discussed in the context of triaxial projected shell model (TPSM). The energies of observed positive- and negative-parity bands agree with the predictions of the TPSM by considering triaxial deformation for the observed excited band structures. The shape evolution with increasing angular momentum is explained in the framework of cranked shell model (CSM) and the total Routhian surface (TRS) calculations.

The two Gamow-Teller (GT) branches connecting the double-$\beta$ decay partners (${}^{116}\mathrm{Cd}$, ${}^{116}\mathrm{Sn}$) and (${}^{150}\mathrm{Nd}$, ${}^{150}\mathrm{Sm}$) with the intermediate nuclei ${}^{116}\mathrm{In}$ and ${}^{150}\mathrm{Pm}$ are studied within a microscopic approach based on a deformed proton-neutron quasiparticle random-phase approximation built on a Skyrme self-consistent mean field with pairing correlations and spin-isospin residual forces. The results are compared with the experimental GT strength distributions extracted from charge-exchange reactions. After combining the two branches, the nuclear matrix elements for the two-neutrino double-$\beta$ decay are evaluated and compared to experimental values derived from the measured half-lives.

The reaction ${}^{58}\mathrm{Ni}$($\vec{p},{}^3\mathrm{He}){}^{56}\mathrm{Co}$ to several discrete, low-lying states in ${}^{56}\mathrm{Co}$ was investigated. Angular distributions of the analyzing power as well as differential cross sections are presented at incident energies of 80, 100, and 118 MeV. Macroscopic zero-range distorted-wave Born approximation calculations are in fairly good agreement with the experimental data in this incident energy range. This has important implications for studies of inclusive reactions in which light composite particles are emitted.

We examine the effect of first forbidden (FF) decays on $\beta$-decay neutrino spectra by performing microscopic nuclear structure calculations. By analyzing the FF decay branches of even-even nuclei, we conclude that FF decays may be responsible for part of the missing neutrinos in the so-called reactor neutrino anomaly. Further calculations and more experimental data are needed for a firm conclusion.

We study viscosity of the neutron star matter and $r$-mode instability in rotating neutron stars. Contributions to the shear and bulk viscosities from various processes are calculated accounting for in-medium modifications of the nucleon-nucleon interaction. A softening of the pion mode at densities larger than the nuclear saturation density $n_0$ and a possibility of the pion condensation at densities above $3n_0$ are included. The neutron-neutron and proton-proton pairings are incorporated where necessary. In the shear viscosity we include the lepton contribution calculated taking into account the Landau damping in the photon exchange, the nucleon contribution described by the medium-modified one-pion exchange, and some other terms, such as the novel phonon contribution in the $1S_0$ superfluid neutron phase and the neutrino term in the neutrino opacity region. The nucleon shear viscosity depends on the density rather moderately and proves to be much less than the lepton term. On the contrary, among the terms contributing to the bulk viscosity, induced by the delay of the relaxation of lepton concentrations in the star matter perturbed by the $r$-modes, the term from the two-nucleon medium-modified Urca reactions possesses strongest density dependence (rising by several orders of magnitude for massive stars) because of the pion softening. Also, contributions to the bulk viscosity arising from other reactions induced by charged weak currents, e.g., in the Urca processes on a pion condensate and in direct Urca processes, are included. The radiative bulk viscosity induced by charged and neutral weak currents in the region of the neutrino transparency of the star is also calculated accounting for in-medium effects. We exploit the equation of state, which is similar to the Akmal-Pandharipande-Ravenhall equation of state up to $4n_0$, but is stiffer at higher densities, producing the maximum neutron star mass compatible with observations. The direct Urca processes do not appear up to $5n_0$ (corresponding to the star mass $M\simeq 1.9M_{\odot }$). Computed with account of in-medium effects, the frequency boundary of the $r$-mode stability for the stars with the mass $\gtrsim 1.8M_{\odot }$ proves to be above the frequencies of all rotating young pulsars. However, none of the conventional contributions to the viscosity are able to explain the stability of rapid rotation of old recycled pulsars in x-ray binaries. To solve this problem we propose a novel efficient mechanism associated with the appearance of condensates of low-lying modes of bosonic excitations with finite momentum and/or with an enhancement of the inhomogeneous pion/kaon condensates in some parts of the star, if the angular velocity exceeds a critical value.

We show that electrons can couple to the neutron excitations in neutron stars, and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.

We investigate the effects of the $3N$ interaction, which effectively adds a density-dependent term to the LS channel, on the isotopes shifts of the Pb nuclei. With the strength so as to keep the $\ell s$ splitting of the single-nucleon orbits, the density dependence in the LS channel tends to shrink the wave functions of the $j=\ell +1/2$ orbits while making the $j=\ell -1/2$ functions distribute more broadly. Thereby the kink in the isotope shifts of the Pb nuclei at $N=126$ becomes stronger, owing to the attraction from neutrons occupying $0i_{11/2}$ in $N>126$. The density dependence in the LS channel enables us to reproduce the data of the isotope shifts by the Hartree-Fock-Bogoliubov calculations in a long chain of neutron numbers, even without degeneracy between the $n1g_{9/2}$ and $n0i_{11/2}$ levels. We exemplify it by the semirealistic M3Y-P6 interaction.

We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-$\beta$ decays with a state-of-the-art beyond-mean-field covariant density functional theory. The dynamic effects of particle-number and angular-momentum conservations as well as quadrupole shape fluctuations are taken into account with projections and generator coordinate method for both initial and final nuclei. The full relativistic transition operator is adopted to calculate the NMEs. The present systematic studies show that in most of the cases there is a much better agreement with the previous nonrelativistic calculation based on the Gogny force than in the case of the nucleus ${}^{150}\mathrm{Nd}$ found by Song et al. [Phys. Rev. C 90, 054309 (2014)]. In particular, we find that the total NMEs can be well approximated by the pure axial-vector coupling term with a considerable reduction of the computational effort.

A set of global optical potential parameters describing the $A=3$ particles (${}^3\mathrm{He}$ and ${}^3\mathrm{H}$) elastic scattering from $1p$-shell nuclei, $\mathrm{HT}1p$, is obtained by simultaneously fitting 118 sets of experimental data of ${}^3\mathrm{He}$ and ${}^3\mathrm{H}$ elastic scattering from ${}^9\mathrm{Be},{}^{10}\mathrm{B},{}^{11}\mathrm{B},{}^{12}\mathrm{C},{}^{13}\mathrm{C},{}^{14}\mathrm{C},{}^{14}\mathrm{N},{}^{15}\mathrm{N},{}^{16}\mathrm{O},{}^{17}\mathrm{O}$, and ${}^{18}\mathrm{O}$ with incident energies from $4\le E\le 118.5$ MeV and 24 sets of elastic scattering data with the ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ targets from $3\le E\le 44$ MeV. $\mathrm{HT}1p$ is found to be superior to GDP08 [D. Y. Pang, P. Roussel-Chomaz, H. Savajols, R. L. Varner, and R. Wolski, Phys. Rev. C 79, 024615 (2009)], which is a systematic potential designed for the heavy-target region, in the reproduction of the angular distributions of elastic scattering cross sections of ${}^3\mathrm{He}$ and ${}^3\mathrm{H}$ from $1p$-shell nuclei at energies below 100 MeV. At energies above 100 MeV, GDP08 is found to be better than HT1p.

The ${}^6\mathrm{Li}+{}^6\mathrm{Li}$ $\to 3\alpha$ reaction was measured in a kinematically complete experiment at 3.1 and 2.5 MeV to investigate the presence of quasifree processes at sub-Coulomb energies. Results from the present experiment show a very clear evidence of quasifree mechanisms with an $\alpha$-particle spectator either in the target or in the projectile. To check the occurrence of quasifree processes, “energy sharing” and “angular correlation” analyses have been performed in the framework of the plane wave impulse approximation, both leading to consistent results. The huge peak in the angular correlation spectra, previously ascribed to the “anomalous quasifree” process, corresponds instead to the population of the 22.2-MeV $(2^{+},\Gamma =800$ keV) state of ${}^8\mathrm{Be}$.