We analyze the spin asymmetry for single inclusive jet production in proton-proton collisions collected by the AnDY experiment at the Relativistic Heavy Ion Collider and the Sivers asymmetry data from semi-inclusive deep inelastic scattering experiments. In particular, we consider the role color gauge invariance plays in determining the process dependence of the Sivers effect. We find that after carefully taking into account the initial-state and final-state interactions between the active parton and the remnant of the polarized hadron, the calculated jet spin asymmetry based on the Sivers functions extracted from HERMES and COMPASS experiments is consistent with the AnDY experimental data. This provides a first indication for the process dependence of the Sivers effect in these processes. We also make predictions for both direct photon and Drell-Yan spin asymmetry, to further test the process dependence of the Sivers effect in future experiments.

Neutrinoless double beta decay, if observed, could distinguish whether the neutrino is a Dirac or a Majorana particle, and it could be used to determine the absolute scale of the neutrino masses. ${}^{136}\mathrm{Xe}$ is one of the most promising candidates for observing this rare event. However, until recently there were no positive results for the allowed and less rare two-neutrino double beta decay mode. The small nuclear matrix element associated with the long half-life represents a challenge for nuclear structure models used for its calculation. We report a new shell-model analysis of the two-neutrino double beta decay of ${}^{136}\mathrm{Xe}$, which takes into account all relevant nuclear orbitals necessary to fully describe the associated Gamow-Teller strength. We further use the new model to analyze the main contributions to the neutrinoless double beta decay matrix element, and show that they are also diminished.

Ground-state two-proton ($2p$) radioactivity is a decay mode found in isotopes of elements with even atomic numbers located beyond the two-proton drip line. So far, this exotic process has been experimentally observed in a few light- and medium-mass nuclides with $Z\le 30$. In this study, using state-of-the-art nuclear density functional theory, we globally analyze $2p$ radioactivity and for the first time identify $2p$-decay candidates in elements heavier than strontium. We predict a few cases where the competition between $2p$ emission and $\alpha$ decay may be observed. In nuclei above lead, the $\alpha$-decay mode is found to be dominating and no measurable candidates for the $2p$ radioactivity are expected.

The compatibility of neutrino-nucleus deep inelastic scattering data within the universal, factorizable nuclear parton distribution functions has been studied independently by several groups in the past few years. The conclusions are contradictory, ranging from a violation of the universality up to a good agreement, most of the controversy originating from the use of the neutrino-nucleus data from the NuTeV Collaboration. Here, we pay attention to non-negligible differences in the absolute normalization between different neutrino data sets. We find that such variations are large enough to prevent a tensionless fit to all data simultaneously and could therefore misleadingly point towards nonuniversal nuclear effects. We propose a concrete method to deal with the absolute normalization and show that an agreement between independent neutrino data sets is established.

The first measurement of the three-body photodisintegration of longitudinally polarized ${}^3\mathrm{He}$ with a circularly polarized $\gamma$-ray beam was carried out at the High Intensity $\gamma$-ray Source facility located at Triangle Universities Nuclear Laboratory. The spin-dependent double-differential cross sections and the contributions from the three-body photodisintegration to the ${}^3\mathrm{He}$ Gerasimov-Drell-Hearn integrand are presented and compared with state-of-the-art three-body calculations at the incident photon energies of 12.8 and 14.7 MeV. The data reveal the importance of including the Coulomb interaction between protons in three-body calculations.

We argue that the domain structure of deconfined QCD matter, which can be inferred from the properties of the Polyakov loop, can simultaneously explain the two most prominent experimentally verified features of the quark-gluon plasma, namely its large opacity as well as its near ideal fluid properties.

The astrophysical $S$ factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0–100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants entering the weak current operators are fixed so as to reproduce the $A=3$ binding energies and magnetic moments and the Gamow-Teller matrix element in tritium $\beta$ decay. Contributions from $S$ and $P$ partial waves in the incoming two-proton channel are retained. The $S$ factor at zero energy is found to be $S(0)=(4.030\pm 0.006)\times {10}^{-23}\mathrm{MeV}{\mathrm{fm}}^2$, with a $P$-wave contribution of $0.020\times {10}^{-23}\mathrm{MeV}{\mathrm{fm}}^2$. The theoretical uncertainty is due to the fitting procedure of the low-energy constants and to the cutoff dependence.

Recent measurements of the azimuthal anisotropy of direct photons in heavy-ion collisions at the energies of Relativistic Heavy Ion Collider show that it is of the same order as the hadronic one. This finding appears to contradict the expected dominance of photon production from a quark-gluon plasma at an early stage of a heavy-ion collision. A possible explanation of the strong azimuthal anisotropy of the photons, given recently, is based on the presence of a large magnetic field in the early phase of a collision. In this Letter, we propose a method to experimentally measure the degree to which a magnetic field in heavy-ion collisions is responsible for the observed anisotropy of photon production. The experimental test proposed in this Letter may potentially change our understanding of the nonequilibrium stage and possible thermalization in heavy-ion collisions.

We optimize the nucleon-nucleon interaction from chiral effective field theory at next-to-next-to-leading order (NNLO). The resulting new chiral force ${\mathrm{NNLO}}_{\mathrm{opt}}$ yields ${\chi }^2\approx 1$ per degree of freedom for laboratory energies below approximately 125 MeV. In the $A=3$, 4 nucleon systems, the contributions of three-nucleon forces are smaller than for previous parametrizations of chiral interactions. We use ${\mathrm{NNLO}}_{\mathrm{opt}}$ to study properties of key nuclei and neutron matter, and we demonstrate that many aspects of nuclear structure can be understood in terms of this nucleon-nucleon interaction, without explicitly invoking three-nucleon forces.

The neutron-rich isotopes of cadmium up to the $N=82$ shell closure have been investigated by high-resolution laser spectroscopy. Deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in ${}^{127}\mathrm{Cd}$ and ${}^{129}\mathrm{Cd}$ for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the $11/2^{-}$ quadrupole moments. Remarkably, this mechanism is found to act well beyond the $h_{11/2}$ shell.

We study the electric conductivity of hot QCD matter at various temperatures $T$ within the off-shell parton-hadron-string dynamics transport approach for interacting partonic, hadronic or mixed systems in a finite box with periodic boundary conditions. The response of the strongly interacting system in equilibrium to an external electric field defines the electric conductivity ${\sigma }_0$. We find a sizable temperature dependence of the ratio ${\sigma }_0/T$ well in line with calculations in a relaxation time approach for $T_c<T<2.5T_c$. The ratio drops in the hadronic phase with $T$, shows a minimum close to $T_c$, and becomes approximately constant ($\sim 0.3$) above $\sim 5T_c$. Our findings imply that the QCD matter even at $T\approx T_c$ is a much better electric conductor than Cu or Ag (at room temperature).

Two-particle correlations in relative azimuthal angle ($\Delta \varphi$) and pseudorapidity ($\Delta \eta$) are measured in $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ $p+\mathrm{Pb}$ collisions using the ATLAS detector at the LHC. The measurements are performed using approximately $1\mu {\mathrm{b}}^{-1}$ of data as a function of transverse momentum ($p_{\mathrm{T}}$) and the transverse energy ($\Sigma E_{\mathrm{T}}^{\mathrm{Pb}}$) summed over $3.1<\eta <4.9$ in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range ($2<|\Delta \eta |<5$) “near-side” ($\Delta \varphi \sim 0$) correlation that grows rapidly with increasing $\Sigma E_{\mathrm{T}}^{\mathrm{Pb}}$. A long-range “away-side” ($\Delta \varphi \sim \pi$) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small $\Sigma E_{\mathrm{T}}^{\mathrm{Pb}}$, is found to match the near-side correlation in magnitude, shape (in $\Delta \eta$ and $\Delta \varphi$) and $\Sigma E_{\mathrm{T}}^{\mathrm{Pb}}$ dependence. The resultant $\Delta \varphi$ correlation is approximately symmetric about $\pi /2$, and is consistent with a dominant $\cos 2\Delta \varphi$ modulation for all $\Sigma E_{\mathrm{T}}^{\mathrm{Pb}}$ ranges and particle $p_{\mathrm{T}}$.

For mirror nuclei with masses $A=42–95$, the effects of isospin-nonconserving nuclear forces are studied with the nuclear shell model using the Coulomb displacement energy and triplet displacement energy as probes. It is shown that the characteristic behavior of the displacement energies can be well reproduced if the isovector and isotensor nuclear interactions with $J=0$ and $T=1$ are introduced into the $f_{7/2}$ shell. These forces, with their strengths being found consistent with the nucleon-nucleon scattering data, tend to modify nuclear binding energies near the $N=Z$ line. At present, no evidence is found that these forces are needed for the upper $fp$ shell. Theoretical one- and two-proton separation energies are predicted accordingly, and locations of the proton drip line are thereby suggested.

Distributions of the largest fragment charge, $Z_{\max }$, in multifragmentation reactions around the Fermi energy can be decomposed into a sum of a Gaussian and a Gumbel distribution, whereas at much higher or lower energies one or the other distribution is asymptotically dominant. We demonstrate the same generic behavior for the largest cluster size in critical aggregation models for small systems, in or out of equilibrium, around the critical point. By analogy with the time-dependent irreversible aggregation model, we infer that $Z_{\max }$ distributions are characteristic of the multifragmentation time scale, which is largely determined by the onset of radial expansion in this energy range.

Two distinct sets of chiral-partner bands have been identified in the nucleus ${}^{133}\mathrm{Ce}$. They constitute a multiple chiral doublet, a phenomenon predicted by relativistic mean field (RMF) calculations and observed experimentally here for the first time. The properties of these chiral bands are in good agreement with results of calculations based on a combination of the constrained triaxial RMF theory and the particle-rotor model.

A measurement of the reduced transition probability for the excitation of the ground state to the first $2^{+}$ state in ${}^{104}\mathrm{Sn}$ has been performed using relativistic Coulomb excitation at GSI. ${}^{104}\mathrm{Sn}$ is the lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus ${}^{100}\mathrm{Sn}$. The value $B(E2;0^{+}\to 2^{+})=0.10(4)$ $e^2{b}^2$ is significantly lower than earlier results for ${}^{106}\mathrm{Sn}$ and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust $N=Z=50$ shell closure.

We report on a new measurement of the neutron $\beta$-asymmetry parameter $A$ with the instrument Perkeo II. The main enhancements are the high neutron polarization of $P=99.7(1)\%$ from a novel arrangement of supermirror polarizers and reduced background from improvements in beam line and shielding. The leading corrections were thus reduced by a factor of 4, pushing them below the level of statistical error and resulting in a significant reduction of systematic uncertainty compared to our previous experiments. We derive the $\beta$-asymmetry parameter $A_0=-0.11972(45{)}_{\mathrm{stat}}{(}_{-44}^{+32}{)}_{\mathrm{sys}}=-0.11972{(}_{-65}^{+53})$ and the ratio of the axial vector to the vector coupling constant $\lambda =g_A/g_V=-1.2761(12{)}_{\mathrm{stat}}{(}_{-12}^{+9}{)}_{\mathrm{sys}}=-1.2761{(}_{-17}^{+14})$.

The ground-state spins and magnetic moments of ${}^{49,51}\mathrm{K}$ have been measured using bunched-beam high-resolution collinear laser spectroscopy at ISOLDE CERN. For ${}^{49}\mathrm{K}$ a ground-state spin $I=1/2$ was firmly established. The observed hyperfine structure of ${}^{51}\mathrm{K}$ requires a spin $I>1/2$ and strongly suggests $I=3/2$. From its magnetic moment $\mu ({}^{51}\mathrm{K})=+0.5129(22){\mu }_N$ a spin-parity $I^{\pi }=3/2^{+}$ with a dominant $\pi 1d_{3/2}^{-1}$ hole configuration was deduced. This establishes for the first time the reinversion of the single-particle levels and illustrates the prominent role of the residual monopole interaction for single-particle levels and shell evolution.

Comprehensive and high-accuracy $\overrightarrow{n}\mathrm{\text{−}}{}^3\mathrm{He}$ elastic scattering analyzing power $A_y(\theta )$ angular distributions were obtained at five incident neutron energies between 1.60 and 5.54 MeV. The data are compared to rigorous four-nucleon calculations using high-precision nucleon-nucleon potential models; three-nucleon force effects are found to be very small. The agreement between data and calculations is fair at the lower energies and becomes less satisfactory with increasing neutron energy. Comparison to $p\mathrm{\text{−}}{}^3\mathrm{He}$ scattering over the same energy range exhibits unexpectedly large isospin effects.

We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudorapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the fluctuations at the LHC are smaller compared to the measurements at the BNL Relativistic Heavy Ion Collider, and as such, closer to what has been theoretically predicted for the formation of a quark-gluon plasma.