The second Fourier component $v_2$ of the azimuthal anisotropy with respect to the reaction plane is measured for direct photons at midrapidity and transverse momentum ($p_T$) of $1–12\mathrm{GeV}/c$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. Previous measurements of this quantity for hadrons with $p_T<6\mathrm{GeV}/c$ indicate that the medium behaves like a nearly perfect fluid, while for $p_T>6\mathrm{GeV}/c$ a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for $p_T>4\mathrm{GeV}/c$ the anisotropy for direct photons is consistent with zero, which is as expected if the dominant source of direct photons is initial hard scattering. However, in the $p_T<4\mathrm{GeV}/c$ region dominated by thermal photons, we find a substantial direct-photon $v_2$ comparable to that of hadrons, whereas model calculations for thermal photons in this kinematic region underpredict the observed $v_2$.

The effects of energy loss in cold nuclear matter on $J/\psi$ suppression in $p\mathrm{\text{−}}A$ collisions are studied. A simple model based on first principles and depending on a single free parameter is able to reproduce $J/\psi$ suppression data at large $x_F$ and at various center-of-mass energies. These results strongly support energy loss as a dominant effect in quarkonium suppression. They also give some hint on its hadroproduction mechanism suggesting color neutralization to happen on long time scales. Predictions for $J/\psi$ and ${\rm Y}$ suppression in $p$-Pb collisions at the LHC are made.

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, $2.5<y<4$, in $pp$ and Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$. The $p_t$-differential inclusive cross section of muons from heavy-flavor decays in $pp$ collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of $p_t$ and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3–4 is observed in $6<p_t<10\mathrm{GeV}/c$. The suppression shows no significant $p_t$ dependence.

The $\beta$ decays of neutron-rich nuclei near the doubly magic ${}^{78}\mathrm{Ni}$ were studied at the Holifield Radioactive Ion Beam Facility using an electromagnetic isobar separator. The half-lives of ${}^{82}\mathrm{Zn}$ ($228\pm 10\mathrm{ms}$), ${}^{83}\mathrm{Zn}$ ($117\pm 20\mathrm{ms}$), and ${}^{85}\mathrm{Ga}$ ($93\pm 7\mathrm{ms}$) were determined for the first time. These half-lives were found to be very different from the predictions of the global model used in astrophysical simulations. A new calculation was developed using the density functional model, which properly reproduced the new experimental values. The robustness of the new model in the ${}^{78}\mathrm{Ni}$ region allowed us to extrapolate data for more neutron-rich isotopes. The revised analysis of the rapid neutron capture process in low entropy environments with our new set of measured and calculated half-lives shows a significant redistribution of predicted isobaric abundances strengthening the yield of $A>140$ nuclei.

We introduced recently a new theoretical scheme which accounts for hydrodynamically expanding bulk matter, jets, and the interaction between the two. Important for the particle production at intermediate values of transverse momentum ($p_t$) are jet hadrons produced inside the fluid. They pick up quarks and antiquarks (or diquarks) from the thermal matter rather than creating them via the Schwinger mechanism—the usual mechanism of hadron production from string fragmentation. These hadrons carry plasma properties (flavor, flow) but also the large momentum of the transversely moving string segment connecting quark and antiquark (or diquark). They therefore show up at quite large values of $p_t$, not polluted by soft particle production. We will show that this mechanism leads to a pronounced peak in the Lambda-to-kaon ratio at intermediate $p_t$. The effect increases substantially with centrality, which reflects the increasing transverse size with centrality.

Isochronous mass spectrometry has been applied to neutron-deficient ${}^{58}\mathrm{Ni}$ projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of a series of short-lived $T_z=-3/2$ nuclides including ${}^{41}\mathrm{Ti}$, ${}^{45}\mathrm{Cr}$, ${}^{49}\mathrm{Fe}$, and ${}^{53}\mathrm{Ni}$ have been measured with a precision of 20–40 keV. The new data enable us to test for the first time the isobaric multiplet mass equation (IMME) in $fp$-shell nuclei. We observe that the IMME is inconsistent with the generally accepted quadratic form for the $A=53$, $T=3/2$ quartet. We perform full space shell model calculations and compare them with the new experimental results.

The anomaly in Coulomb energy differences (CEDs) between the isospin $T=1$ states in the odd-odd $N=Z$ nucleus ${}^{70}\mathrm{Br}$ and the analogue states in its even-even partner ${}^{70}\mathrm{Se}$ has remained a puzzle. This is a direct manifestation of isospin-symmetry breaking in effective nuclear interactions. Here, we perform large-scale shell-model calculations for nuclei with $A=66$ to 78 using the new filter diagonalization method based on the Sakurai-Sugiura algorithm. The calculations reproduce well the experimental CED. The observed negative CED for $A=70$ are accounted for by the cross-shell neutron excitations from the $fp$ shell to the $g_{9/2}$ intruder orbit with the enhanced electromagnetic spin-orbit contribution at this special nucleon number.

The $0_2^{+}$ state in ${}^{34}\mathrm{Si}$ has been populated at the GANIL-LISE3 facility through the $\beta$ decay of a newly discovered $1^{+}$ isomer in ${}^{34}\mathrm{Al}$ of 26(1) ms half-life. The simultaneous detection of $e^{+}{e}^{-}$ pairs allowed the determination of the excitation energy $E(0_2^{+})=2719(3)\mathrm{keV}$ and the half-life $T_{1/2}=19.4(7)\mathrm{ns}$, from which an electric monopole strength of ${\rho }^2(E0)=13.0(0.9)\times {10}^{-3}$ was deduced. The $2_1^{+}$ state is observed to decay both to the $0_1^{+}$ ground state and to the newly observed $0_2^{+}$ state [via a 607(2) keV transition] with a ratio $R(2_1^{+}\to 0_1^{+}/2_1^{+}\to 0_2^{+})=1380(717)$. Gathering all information, a weak mixing with the $0_1^{+}$ and a large deformation parameter of $\beta =0.29(4)$ are found for the $0_2^{+}$ state, in good agreement with shell model calculations using a new sdpf-u-mix interaction allowing $np\mathrm{\text{−}}nh$ excitations across the $N=20$ shell gap.

While bulk properties of stable nuclei are successfully reproduced by mean-field theories employing effective interactions, the dependence of the centroid energy of the electric giant dipole resonance on the nucleon number $A$ is not. This problem is cured by considering many-particle correlations beyond mean-field theory, which we do within the quasiparticle time blocking approximation. The electric giant dipole resonances in ${}^{16}\mathrm{O}$, ${}^{40}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$ are calculated using two new Skyrme interactions.

Only one-third of the nucleons in ${}^{208}\mathrm{Pb}$ occupy the saturation density area. Consequently, nuclear observables related to the average properties of nuclei, such as masses or radii, constrain the equation of state not at the saturation density but rather around the so-called crossing density, localized close to the mean value of the density of nuclei: $\rho \simeq 0.11{\mathrm{fm}}^{-3}$. This provides an explanation for the empirical fact that several equation of state quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative $M$ of the energy per unit of volume at the crossing density is constrained by the giant monopole resonance measurements in an isotopic chain rather than the incompressibility at saturation density. The giant monopole resonance measurements provide $M=1100\pm 70\mathrm{MeV}$ (6% uncertainty), whose extrapolation gives $K_{\infty }=230\pm 40\mathrm{MeV}$ (17% uncertainty).

The ALICE experiment has measured the inclusive $J/\psi$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ down to zero transverse momentum in the rapidity range $2.5<y<4$. A suppression of the inclusive $J/\psi$ yield in Pb-Pb is observed with respect to the one measured in $pp$ collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%–80% most central collisions, is $0.545\pm 0.032(\mathrm{stat})\pm 0.083(\mathrm{syst})$ and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including $J/\psi$ production from charm quarks in a deconfined partonic phase can describe our data.

The pseudospin symmetry (PSS) is a relativistic dynamical symmetry connected with the small component of the Dirac spinor. The origin of PSS in single particle bound states in atomic nuclei has been revealed and studied extensively. By examining the zeros of Jost functions corresponding to the small components of Dirac wave functions and phase shifts of continuum states, we show that the PSS in single particle resonant states in nuclei is conserved when the attractive scalar and repulsive vector potentials have the same magnitude but opposite sign. The exact conservation and the breaking of the PSS are illustrated for single particle resonances in spherical square-well and Woods-Saxon potentials.

We demonstrate that, in the framework of the event-by-event hydrodynamics followed by statistical hadronization, the proper charge conservation in the mechanism of hadron production provides the crucial nonflow component and leads to agreement with the two-dimensional two-particle correlation data in relative azimuthal angle and pseudorapidity at soft transverse momenta ($p_T<2\mathrm{GeV}$). The falloff of the same-side ridge in relative pseudorapidity follows from the fact that a pair of particles with balanced charges is emitted from the same fluid element, whose collective velocity collimates the momenta of the pair. We reproduce basic experimental features of the two-dimensional correlation function, such as the dependence on the relative charge and centrality, as well as the related charge balance functions and the harmonic flow coefficients as functions of the relative pseudorapidity.

Quantum vortices in the color-flavor locked phase of QCD have bosonic degrees of freedom, called the orientational zero modes, localized on them. We show that the orientational zero modes are electromagnetically charged. As a result, a vortex in the color-flavor locked phase nontrivially interacts with photons. We show that a lattice of vortices acts as a polarizer of photons with wavelengths larger than some critical length.

We study the use of truncated normal-ordered three-nucleon interactions in nuclear structure calculations starting from chiral two- plus three-nucleon Hamiltonians evolved consistently with the similarity renormalization group. We present three key developments: (i) a rigorous benchmark of the normal-ordering approximation in the importance-truncated no-core shell model for ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$; (ii) a direct comparison of the importance-truncated no-core shell model results with coupled-cluster calculations at the singles and doubles level for ${}^{16}\mathrm{O}$; and (iii) first applications of similarity renormalization group-evolved chiral $NN+3N$ Hamiltonians in coupled-cluster calculations for medium-mass nuclei ${}^{16,24}\mathrm{O}$ and ${}^{40,48}\mathrm{Ca}$. We show that the normal-ordered two-body approximation works very well beyond the lightest isotopes and opens a path for studies of medium-mass and heavy nuclei with chiral two- plus three-nucleon interactions. At the same time we highlight the predictive power of chiral Hamiltonians.

We report a precise determination of the ${}^{19}\mathrm{Ne}$ half-life to be $T_{1/2}=17.262\pm 0.007\mathrm{s}$. This result disagrees with the most recent precision measurements and is important for placing bounds on predicted right-handed interactions that are absent in the current standard model. We are able to identify and disentangle two competing systematic effects that influence the accuracy of such measurements. Our findings prompt a reassessment of results from previous high-precision lifetime measurements that used similar equipment and methods.

Neutrinoless double-$\beta$ decay is of fundamental importance for the determining neutrino mass. By combining a calculation of nuclear matrix elements within the framework of the microscopic interacting boson model with an improved calculation of phase space factors, we set limits on the average light neutrino mass and on the average inverse heavy neutrino mass (flavor-violating parameter).

We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number $N=32$. Using the TITAN system, the mass of ${}^{51}\mathrm{K}$ was measured for the first time, and the precision of the ${}^{51,52}\mathrm{Ca}$ mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, ${}^{52}\mathrm{Ca}$ is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces.

The nucleus ${}^{49}\mathrm{Sc}$, having a single $f_{7/2}$ proton outside doubly magic ${}^{48}\mathrm{Ca}$ ($Z=20$, $N=28$), is one of the very few isotopes which makes possible testing of the fundamental theory of nuclear magnetism. The magnetic moment has been measured by online $\beta$ NMR of nuclei oriented at milli-Kelvin temperatures to be $(+)5.616(25){\mu }_N$. The result is discussed in terms of a detailed theory of the structure of the magnetic moment operator, showing excellent agreement with calculated departure from the $f_{7/2}$ Schmidt limit extreme single-particle value. The measurement completes the sequence of moments of Sc isotopes with even numbers of $f_{7/2}$ neutrons: the first such isotopic chain between two major shells for which a full set of moment measurements exists. The result further completes the isotonic sequence of ground-state moments of nuclei with an odd number of $f_{7/2}$ protons coupled to a closed subshell of $f_{7/2}$ neutrons. Comparison with a recent shell-model calculation of the latter sequence is made.

We report on a search for neutrinoless double-beta decay of ${}^{136}\mathrm{Xe}$ with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of $\sim 1.5\times {10}^{-3}{\mathrm{kg}}^{-1}{\mathrm{yr}}^{-1}{\mathrm{keV}}^{-1}$ in the $\pm 1\sigma$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0\nu \beta \beta }({}^{136}\mathrm{Xe})>1.6\times {10}^{25}\mathrm{yr}$ (90% C.L.), corresponding to effective Majorana masses of less than 140–380 meV, depending on the matrix element calculation.