The lifetimes of the first excited $2^{+}$ and $4^{+}$ states in ${}^{72}\mathrm{Ni}$ were measured at the National Superconducting Cyclotron Laboratory with the recoil-distance Doppler-shift method, a model-independent probe to obtain the reduced transition probability. Excited states in ${}^{72}\mathrm{Ni}$ were populated by the one-proton knockout reaction of an intermediate energy ${}^{73}\mathrm{Cu}$ beam. $\gamma$-ray-recoil coincidences were detected with the $\gamma$-ray tracking array GRETINA and the S800 spectrograph. Our results provide evidence of enhanced transition probability $B(E2;2^{+}\to 0^{+})$ as compared to ${}^{68}\mathrm{Ni}$, but do not confirm the trend of large $B(E2)$ values reported in the neighboring isotope ${}^{70}\mathrm{Ni}$ obtained from Coulomb excitation measurement. The results are compared to shell model calculations. The lifetime obtained for the excited $4_1^{+}$ state is consistent with models showing decay of a seniority $\nu =4$, $4^{+}$ state, which is consistent with the disappearance of the $8^{+}$ isomer in ${}^{72}\mathrm{Ni}$.

We present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in $\mathrm{Au}+\mathrm{Au}$ collisions for energies ranging from $\sqrt{s_{NN}}=7.7$ to 200 GeV. The third harmonic $v_3^2\{2\}=⟨\cos 3({\varphi }_1-{\varphi }_2)⟩$, where ${\varphi }_1-{\varphi }_2$ is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs $\mathrm{\Delta }\eta ={\eta }_1-{\eta }_2$. Nonzero $v_3^2\{2\}$ is directly related to the previously observed large-$\mathrm{\Delta }\eta$ narrow-$\mathrm{\Delta }\varphi$ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity quark gluon plasma phase. For sufficiently central collisions, $v_3^2\{2\}$ persist down to an energy of 7.7 GeV, suggesting that quark gluon plasma may be created even in these low energy collisions. In peripheral collisions at these low energies, however, $v_3^2\{2\}$ is consistent with zero. When scaled by the pseudorapidity density of charged-particle multiplicity per participating nucleon pair, $v_3^2\{2\}$ for central collisions shows a minimum near $\sqrt{s_{NN}}=20\mathrm{GeV}$.

We present the nuclear matrix element for the neutrinoless double-beta decay of ${}^{48}\mathrm{Ca}$ based on large-scale shell-model calculations including two harmonic oscillator shells ($sd$ and $pf$ shells). The excitation spectra of ${}^{48}\mathrm{Ca}$ and ${}^{48}\mathrm{Ti}$, and the two-neutrino double-beta decay of ${}^{48}\mathrm{Ca}$ are reproduced in good agreement to the experimental data. We find that the neutrinoless double-beta decay nuclear matrix element is enhanced by about 30% compared to $pf$-shell calculations. This reduces the decay lifetime by almost a factor of 2. The matrix-element increase is mostly due to pairing correlations associated with cross-shell $sd\text{−}pf$ excitations. We also investigate possible implications for heavier neutrinoless double-beta decay candidates.

Two-nucleon systems are shown to exhibit large scattering lengths in strong magnetic fields at unphysical quark masses, and the trends toward the physical values indicate that such features may exist in nature. Lattice QCD calculations of the energies of one and two nucleons systems are performed at pion masses of $m_{\pi }\sim 450$ and 806 MeV in uniform, time-independent magnetic fields of strength $|\mathbf{B}|\sim {10}^{19}–{10}^{20}\mathrm{G}$ to determine the response of these hadronic systems to large magnetic fields. Fields of this strength may exist inside magnetars and in peripheral relativistic heavy ion collisions, and the unitary behavior at large scattering lengths may have important consequences for these systems.

Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive- and negative-parity bands have been identified in ${}^{78}\mathrm{Br}$. They are interpreted as multiple chiral doublet bands with octupole correlations, which is supported by the microscopic multidimensionally-constrained covariant density functional theory and triaxial particle rotor model calculations. This observation reports the first example of chiral geometry in octupole soft nuclei.

The unbound nucleus ${}^{26}\mathrm{O}$ has been investigated using invariant-mass spectroscopy following one-proton removal reaction from a ${}^{27}\mathrm{F}$ beam at $201\mathrm{MeV}/\mathrm{nucleon}$. The decay products, ${}^{24}\mathrm{O}$ and two neutrons, were detected in coincidence using the newly commissioned SAMURAI spectrometer at the RIKEN Radioactive Isotope Beam Factory. The ${}^{26}\mathrm{O}$ ground-state resonance was found to lie only $18\pm 3(\mathrm{stat})\pm 4(\mathrm{syst})\mathrm{keV}$ above threshold. In addition, a higher lying level, which is most likely the first $2^{+}$ state, was observed for the first time at ${1.28}_{-0.08}^{+0.11}\mathrm{MeV}$ above threshold. Comparison with theoretical predictions suggests that three-nucleon forces, $pf$-shell intruder configurations, and the continuum are key elements to understanding the structure of the most neutron-rich oxygen isotopes beyond the drip line.

The astrophysical $S$ factor for the radiative capture $d(p,\gamma ){}^3\mathrm{He}$ in the energy range of interest for big bang nucleosynthesis (BBN) is calculated using an ab initio approach. The nuclear Hamiltonian retains both two- and three-nucleon interactions—the Argonne $v_{18}$ and the Urbana IX, respectively. Both one- and many-body contributions to the nuclear current operator are included. The former retain for the first time, besides the $1/m$ leading order contribution ($m$ is the nucleon mass), also the next-to-leading order term, proportional to $1/m^3$. The many-body currents are constructed in order to satisfy the current conservation relation with the adopted Hamiltonian model. The hyperspherical harmonics technique is applied to solve the $A=3$ bound and scattering states. Particular attention is paid in this second case in order to obtain, in the energy range of BBN, an uncertainty on the astrophysical $S$ factor of the order or below $\sim 1\%$. Then, in this energy range, the $S$ factor is found to be $\sim 10\%$ larger than the currently adopted values. Part of this increase (1%–3%) is due to the $1/m^3$ one-body operator, while the remaining is due to the new more accurate scattering wave functions. We have studied the implication of this new determination for the $d(p,\gamma ){}^3\mathrm{He}$ $S$ factor on the deuterium primordial abundance. We find that the predicted theoretical value for ${}^2\mathrm{H}/\mathrm{H}$ is in excellent agreement with its experimental determination, using the most recent determination of the baryon density of the Planck experiment, and with a standard number of relativistic degrees of freedom $N_{\text{eff}}=3.046$ during primordial nucleosynthesis. This calls for a more accurate measurement of the astrophysical $S$ factor in order to confirm the present predictions.

We report the first use of the effective quark-meson coupling (QMC) energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the nonrelativistic Hartree-$\text{Fock}+\mathrm{BCS}$ framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having a clear physics basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist, however, multiple Skyrme parameter sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter.

The collective behavior of hadronic particles has been observed in high multiplicity proton-lead collisions at the Large Hadron Collider, as well as in deuteron-gold collisions at the Relativistic Heavy-Ion Collider. In this work we present the first calculation, in the hydrodynamic framework, of thermal photon radiation from such small collision systems. Owing to their compact size, these systems can reach temperatures comparable to those in central nucleus-nucleus collisions. The thermal photons can thus shine over the prompt background, and increase the low $p_T$ direct photon spectrum by a factor of 2–3 in 0%–1% $p+\mathrm{Pb}$ collisions at 5.02 TeV. This thermal photon enhancement can therefore serve as a signature of the existence of a hot quark-gluon plasma during the evolution of these small collision systems, as well as validate hydrodynamic behavior in small systems.

The atomic mass relations among the mass triplet ${}^{96}\mathrm{Zr}$, ${}^{96}\mathrm{Nb}$, and ${}^{96}\mathrm{Mo}$ have been determined by means of high-precision mass measurements using the JYFLTRAP mass spectrometer at the IGISOL facility of the University of Jyväskylä. We report $Q$ values for the ${}^{96}\mathrm{Zr}$ single and double $\beta$ decays to ${}^{96}\mathrm{Nb}$ and ${}^{96}\mathrm{Mo}$, as well as the $Q$ value for the ${}^{96}\mathrm{Nb}$ single $\beta$ decay to ${}^{96}\mathrm{Mo}$, which are $Q_{\beta }({}^{96}\mathrm{Zr})=163.96(13)$, $Q_{\beta \beta }({}^{96}\mathrm{Zr})=3356.097(86)$, and $Q_{\beta }({}^{96}\mathrm{Nb})=3192.05(16)\mathrm{keV}$. Of special importance is the ${}^{96}\mathrm{Zr}$ single $\beta$-decay $Q$ value, which has never been determined directly. The single $\beta$ decay, whose main branch is fourfold unique forbidden, is an alternative decay path to the ${}^{96}\mathrm{Zr}$ $\beta \beta$ decay, and its observation can provide one of the most direct tests of the neutrinoless $\beta \beta$-decay nuclear-matrix-element calculations, as these can be simultaneously performed for both decay paths with no further assumptions. The theoretical single $\beta$-decay rate has been re-evaluated using a shell-model approach, which indicates a ${}^{96}\mathrm{Zr}$ single $\beta$-decay lifetime within reach of an experimental verification. The uniqueness of the decay also makes such an experiment interesting for an investigation into the origin of the quenching of the axial-vector coupling constant $g_A$.

We present high precision measurements of elliptic flow near midrapidity ($|y|<1.0$) for multistrange hadrons and $\varphi$ meson as a function of centrality and transverse momentum in $\mathrm{Au}+\mathrm{Au}$ collisions at center of mass energy $\sqrt{s_{NN}}=200\mathrm{GeV}$. We observe that the transverse momentum dependence of $\varphi$ and $\mathrm{\Omega }$ $v_2$ is similar to that of $\pi$ and $p$, respectively, which may indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. Number of constituent quark scaling is found to hold within statistical uncertainty for both 0%–30% and 30%–80% collision centrality. There is an indication of the breakdown of previously observed mass ordering between $\varphi$ and proton $v_2$ at low transverse momentum in the 0%–30% centrality range, possibly indicating late hadronic interactions affecting the proton $v_2$.

We present quantum Monte Carlo calculations of light nuclei, neutron-$\alpha$ scattering, and neutron matter using local two- and three-nucleon ($3N$) interactions derived from chiral effective field theory up to next-to-next-to-leading order (${\mathrm{N}}^2\mathrm{LO}$). The two undetermined $3N$ low-energy couplings are fit to the ${}^4\mathrm{He}$ binding energy and, for the first time, to the spin-orbit splitting in the neutron-$\alpha$ $P$-wave phase shifts. Furthermore, we investigate different choices of local $3N$-operator structures and find that chiral interactions at ${\mathrm{N}}^2\mathrm{LO}$ are able to simultaneously reproduce the properties of $A=3,4,5$ systems and of neutron matter, in contrast to commonly used phenomenological $3N$ interactions.

We present a novel nuclear energy density functional method to calculate spectroscopic properties of atomic nuclei. Intrinsic nuclear quadrupole deformations and rotational frequencies are considered simultaneously as the degrees of freedom within a symmetry conserving configuration mixing framework. The present method allows the study of nuclear states with collective and single-particle character. We calculate the fascinating structure of the semimagic ${}^{44}\mathrm{S}$ nucleus as a first application of the method, obtaining an excellent quantitative agreement both with the available experimental data and with state-of-the-art shell model calculations.

Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV ($J^{\pi }=1^{+}$, $T=1$) $\text{state}\to \text{ground}$ state ($J^{\pi }=0^{+}$, $T=0$) and the isoscalar magnetic dipole 18.15 MeV ($J^{\pi }=1^{+}$, $T=0$) $\text{state}\to \text{ground}$ state transitions in ${}^8\mathrm{Be}$. Significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of $>5\sigma$. This observation could possibly be due to nuclear reaction interference effects or might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of $16.70\pm 0.35(\text{stat})\pm 0.5(\text{syst})\mathrm{MeV}/c^2$ and $J^{\pi }=1^{+}$ was created.

The production cross sections of the $B^{+}$, $B^0$, and $B_s^0$ mesons, and of their charge conjugates, are measured via exclusive hadronic decays in $p+\mathrm{Pb}$ collisions at the center-of-mass energy $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ with the CMS detector at the CERN LHC. The data set used for this analysis corresponds to an integrated luminosity of $34.6{\mathrm{nb}}^{-1}$. The production cross sections are measured in the transverse momentum range between 10 and $60\mathrm{GeV}/c$. No significant modification is observed compared to proton-proton perturbative QCD calculations scaled by the number of incoherent nucleon-nucleon collisions. These results provide a baseline for the study of in-medium $b$ quark energy loss in $\mathrm{Pb}+\mathrm{Pb}$ collisions.

Isomer shifts have been determined in ${}^{111–129}\mathrm{Cd}$ by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the $1/2^{+}$ and the $3/2^{+}$ ground states to the $11/2^{-}$ isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory.

In light of the forthcoming high precision quasielastic electron scattering data from Jefferson Lab, it is timely for the various approaches to nuclear structure to make robust predictions for the associated response functions. With this in mind, we focus here on the longitudinal response function and the corresponding Coulomb sum rule for isospin-symmetric nuclear matter at various baryon densities. Using a quantum field-theoretic quark-level approach which preserves the symmetries of quantum chromodynamics, as well as exhibiting dynamical chiral symmetry breaking and quark confinement, we find a dramatic quenching of the Coulomb sum rule for momentum transfers $|q|\gtrsim 0.5\mathrm{GeV}$. The main driver of this effect lies in changes to the proton Dirac form factor induced by the nuclear medium. Such a dramatic quenching of the Coulomb sum rule was not seen in a recent quantum Monte Carlo calculation for carbon, suggesting that the Jefferson Lab data may well shed new light on the explicit role of QCD in nuclei.