The differences in the charge radii of mirror nuclei are shown to be proportional to the derivative of the neutron equation of state and the symmetry energy at nuclear matter saturation density. This derivative is important for constraining the neutron equation of state for use in astrophysics. The charge radii of several neutron-rich nuclei are already measured to the accuracy of about 0.005 fm. Experiments at isotope-separator and radioactive-beam facilities are needed to measure the charge radii of the corresponding proton-rich mirror nuclei to a similar accuracy. It is also shown that neutron skins of nuclei with $N=Z$ depend upon the value of the symmetry energy at a density of $0.10\mathrm{nucleons}/{\mathrm{fm}}^3$.

The isotope ${}^{163}\mathrm{Ho}$ is in many ways the best candidate to perform experiments to investigate the value of the electron neutrino mass. It undergoes an electron capture process to ${}^{163}\mathrm{Dy}$ with an energy available to the decay, $Q_{\mathrm{EC}}$, of about 2.8 keV. According to the present knowledge, this is the lowest $Q_{\mathrm{EC}}$ value for such transitions. Here we discuss a newly obtained spectrum of ${}^{163}\mathrm{Ho}$, taken by cryogenic metallic magnetic calorimeters with ${}^{163}\mathrm{Ho}$ implanted in the absorbers and operated in anticoincident mode for background reduction. For the first time, the atomic deexcitation of the ${}^{163}\mathrm{Dy}$ daughter atom following the capture of electrons from the $5s$ shell in ${}^{163}\mathrm{Ho}$, the OI line, was observed with a calorimetric measurement. The peak energy is determined to be 48 eV. In addition, a precise determination of the energy available for the decay $Q_{\mathrm{EC}}=(2.858\pm 0.010_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}})\mathrm{keV}$ was obtained by analyzing the intensities of the lines in the spectrum. This value is in good agreement with the measurement of the mass difference between ${}^{163}\mathrm{Ho}$ and ${}^{163}\mathrm{Dy}$ obtained by Penning-trap mass spectrometry, demonstrating the reliability of the calorimetric technique.

Current predictions for the antineutrino yield and spectra from a nuclear reactor rely on the experimental electron spectra from ${}^{235}\mathrm{U}$, ${}^{239}\mathrm{Pu}$, ${}^{241}\mathrm{Pu}$ and a numerical method to convert these aggregate electron spectra into their corresponding antineutrino ones. In the present work we investigate quantitatively some of the basic assumptions and approximations used in the conversion method, studying first the compatibility between two recent approaches for calculating electron and antineutrino spectra. We then explore different possibilities for the disagreement between the measured Daya Bay and the Huber-Mueller antineutrino spectra, including the ${}^{238}\mathrm{U}$ contribution as well as the effective charge and the allowed shape assumption used in the conversion method. We observe that including a shape correction of about $+6\%{\mathrm{MeV}}^{-1}$ in conversion calculations can better describe the Daya Bay spectrum. Because of a lack of experimental data, this correction cannot be ruled out, concluding that in order to confirm the existence of the reactor neutrino anomaly, or even quantify it, precisely measured electron spectra for about 50 relevant fission products are needed. With the advent of new rare ion facilities, the measurement of shape factors for these nuclides, for many of which precise beta intensity data from TAGS experiments already exist, would be highly desirable.

In a sufficiently hot and dense astrophysical environment the rate of the triple-alpha ($3\alpha$) reaction can increase greatly over the value appropriate for helium burning stars owing to hadronically induced deexcitation of the Hoyle state. In this Letter we use a statistical model to evaluate the enhancement as a function of temperature and density. For a density of ${10}^6\mathrm{g}{\mathrm{cm}}^{-3}$ enhancements can exceed a factor of 100. In high temperature or density situations, the enhanced $3\alpha$ rate is a better estimate of this rate and should be used in these circumstances. We then examine the effect of these enhancements on production of ${}^{12}\mathrm{C}$ in the neutrino wind following a supernova explosion and in an x-ray burster.

Heavy ion collisions present exciting opportunities to study the effects of quantum coherence in the formation of subatomic particle showers. We report on the first calculation of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet in such collisions. These observables are directly sensitive to the hardest branching within jets and can probe the early stage of the jet formation. We find that the leading-order medium-induced splitting functions, here obtained in the framework of soft-collinear effective theory with Glauber gluon interactions, capture the essential many-body physics, which is different from proton-proton reactions. Qualitative and in most cases quantitative agreement between theory and preliminary CMS measurements suggests that hard parton branching in strongly interacting matter can be dramatically modified. We also propose a new measurement that will illuminate its angular structure.

The measurement of two-particle angular correlations is a powerful tool to study jet quenching in a $p_T$ region inaccessible by direct jet identification. In these measurements pseudorapidity ($\mathrm{\Delta }\eta$) and azimuthal ($\mathrm{\Delta }\phi$) differences are used to extract the shape of the near-side peak formed by particles associated with a higher $p_T$ trigger particle ($1<p_{T,\mathrm{trig}}<8\mathrm{GeV}/c$). A combined fit of the near-side peak and long-range correlations is applied to the data allowing the extraction of the centrality evolution of the peak shape in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$. A significant broadening of the peak in the $\mathrm{\Delta }\eta$ direction at low $p_T$ is found from peripheral to central collisions, which vanishes above $4\mathrm{GeV}/c$, while in the $\mathrm{\Delta }\phi$ direction the peak is almost independent of centrality. For the 10% most central collisions and $1<p_{T,\text{assoc}}<2\mathrm{GeV}/c$, $1<p_{T,\mathrm{trig}}<3\mathrm{GeV}/c$ a novel feature is observed: a depletion develops around the center of the peak. The results are compared to $pp$ collisions at the same center of mass energy and ampt model simulations. The comparison to the investigated models suggests that the broadening and the development of the depletion is connected to the strength of radial and longitudinal flow.

The exotic nucleus ${}^{11}\mathrm{Be}$ has been extensively studied and much experimental information is available on the structure of this system. We treat, within the framework of renormalized nuclear field theory in both configuration and 3D space, the mixing of bound and continuum single-particle states through the coupling to collective vibrations of the ${}^{10}\mathrm{Be}$ core. We also take care of the Pauli principle acting not only between the single valence particle explicitly considered and those participating in the collective states, but also between fermions involved in two-phonon virtual states dressing the single-particle motion. In this way, it is possible to simultaneously and quantitatively account for the energies of the $1/2^{+}$, $1/2^{-}$ low-lying states, the centroid and line shape of the $5/2^{+}$ resonance and the one-nucleon stripping and pickup absolute differential cross sections involving ${}^{11}\mathrm{Be}$ as either target or residual nucleus. Also for the dipole transition connecting the $1/2^{+}$ and $1/2^{-}$ parity inverted levels as well as the isotopic shift of the charge radius. Theory provides a unified and exhaustive nuclear structure and reaction characterization of the many-body effects which are at the basis of this paradigmatic one-neutron halo system.

The existence of ${}^{26}\mathrm{Al}$ ($t_{1/2}=7.17\times {10}^5\mathrm{yr}$) in the interstellar medium provides a direct confirmation of ongoing nucleosynthesis in the Galaxy. The presence of a low-lying $0^{+}$ isomer (${{}^{26}\mathrm{Al}}^m$), however, severely complicates the astrophysical calculations. We present for the first time a study of the ${{}^{26}\mathrm{Al}}^m(d,p){}^{27}\mathrm{Al}$ reaction using an isomeric ${}^{26}\mathrm{Al}$ beam. The selectivity of this reaction allowed the study of $\ell =0$ transfers to $T=1/2$, and $T=3/2$ states in ${}^{27}\mathrm{Al}$. Mirror symmetry arguments were then used to constrain the ${{}^{26}\mathrm{Al}}^m(p,\gamma ){}^{27}\mathrm{Si}$ reaction rate and provide an experimentally determined upper limit of the rate for the destruction of isomeric ${}^{26}\mathrm{Al}$ via radiative proton capture reactions, which is expected to dominate the destruction path of ${{}^{26}\mathrm{Al}}^m$ in asymptotic giant branch stars, classical novae, and core collapse supernovae.

The $p_{\perp }$ dependence of the nuclear modification factor $R_{AA}$ measured in PbPb collisions at the LHC exhibits a universal shape, which can be very well reproduced in a simple energy loss model based on the Baier-Dokshitzer-Mueller-Peigné-Schiff medium-induced gluon spectrum. The scaling is observed for various hadron species ($h^{\pm }$, $D$, $J/\psi$) in different centrality classes and at both colliding energies, $\sqrt{s}=2.76$ and $\sqrt{s}=5.02\mathrm{TeV}$. Results indicate a 10%–20% increase of the transport coefficient from $\sqrt{s}=2.76$ to $\sqrt{s}=5.02\mathrm{TeV}$, consistent with that of particle multiplicity. Based on this model, a data-driven procedure is suggested, which allows for the determination of the first and second moments of the quenching weight without any prior knowledge of the latter.

Calculations of the effects of band structure on the neutron superfluid density in the crust of neutron stars made under the assumption that the effects of pairing are small [N. Chamel, Phys. Rev. C 85, 035801 (2012)] lead to moments of inertia of superfluid neutrons so small that the crust alone is insufficient to account for the magnitude of neutron star glitches. Inspired by earlier work on ultracold atomic gases in an optical lattice, we investigate fermions with attractive interactions in a periodic lattice in the mean-field approximation. The effects of band structure are suppressed when the pairing gap is of order or greater than the strength of the lattice potential. By applying the results to the inner crust of neutron stars, we conclude that the reduction of the neutron superfluid density is considerably less than previously estimated and, consequently, it is premature to rule out models of glitches based on neutron superfluidity in the crust.

We put forward a new ab initio approach that seamlessly bridges the structure, clustering, and reactions aspects of the nuclear quantum many-body problem. The configuration interaction technique combined with the resonating group method based on a harmonic oscillator basis allows us to treat the reaction and multiclustering dynamics in a translationally invariant way and preserve the Pauli principle. Our presentation includes studies of ${}^{8,10}\mathrm{Be}$ and an exploration of $3\alpha$ clustering in ${}^{12}\mathrm{C}$.

We report the results of a $\beta$-decay study of fission products ${}^{86}\mathrm{Br}$, ${}^{89}\mathrm{Kr}$, ${}^{89}\mathrm{Rb}$, ${}^{90gs}\mathrm{Rb}$, ${}^{90m}\mathrm{Rb}$, ${}^{90}\mathrm{Kr}$, ${}^{92}\mathrm{Rb}$, ${}^{139}\mathrm{Xe}$, and ${}^{142}\mathrm{Cs}$ performed with the Modular Total Absorption Spectrometer (MTAS) and on-line mass-separated ion beams. These radioactivities were assessed by the Nuclear Energy Agency as having high priority for decay heat analysis during a nuclear fuel cycle. We observe a substantial increase in $\beta$ feeding to high excited states in all daughter isotopes in comparison to earlier data. This increases the average $\gamma$-ray energy emitted by the decay of fission fragments during the first 10 000 s after fission of ${}^{235}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$ by approximately 2% and 1%, respectively, improving agreement between results of calculations and direct observations. New MTAS results reduce the reference reactor ${\overline{\nu }}_e$ flux used to analyze reactor ${\overline{\nu }}_e$ interaction with detector matter. The reduction determined by the ab initio method for the four nuclear fuel components, ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, ${}^{239}\mathrm{Pu}$, and ${}^{241}\mathrm{Pu}$, amounts to 0.976, 0.986, 0.983, and 0.984, respectively.

The relative phase of the order parameters in the collision of two condensates can influence the outcome of their collision in the case of weak coupling. With increasing interaction strength, however, the initially independent phases of the two order parameters in the colliding partners quickly become phase locked, as the strong coupling favors an overall phase rigidity of the entire condensate, and upon their separation the emerging superfluid fragments become entangled.

A low-energy enhancement of radiative strength functions was deduced from recent experiments in several mass regions of nuclei, which is believed to impact considerably the calculated neutron capture rates. In this Letter we investigate the behavior of the low-energy $\gamma$-ray strength of the ${}^{44}\mathrm{Sc}$ isotope, for the first time taking into account both electric and magnetic dipole contributions obtained coherently in the same theoretical approach. The calculations are performed using the large-scale shell-model framework in a full $1\hslash \omega sd\text{−}pf\text{−}gds$ model space. Our results corroborate previous theoretical findings for the low-energy enhancement of the $M1$ strength but show quite different behavior for the $E1$ strength.

We present the first comparisons of experimental data with phenomenological results from $(3+1)\mathrm{D}$ quasiparticle anisotropic hydrodynamics (aHydroQP). We compare particle spectra, average transverse momentum, and elliptic flow. The dynamical equations used for the hydrodynamic stage utilize aHydroQP, which naturally includes both shear and bulk viscous effects. The $(3+1)\mathrm{D}$ aHydroQP evolution obtained is self-consistently converted to hadrons using anisotropic Cooper-Frye freeze-out. Hadron production and decays are modeled using a customized version of therminator 2. In this first study, we utilized smooth Glauber-type initial conditions and a single effective freeze-out temperature $T_{\mathrm{FO}}=130\mathrm{MeV}$ with all hadronic species in full chemical equilibrium. With this rather simple setup, we find a very good description of many heavy-ion observables.

The threshold anomaly of the phenomenological potential has been known for a long time in nuclear reactions at energies around the Coulomb barrier, where the connection between the real and imaginary potentials is well described by the dispersion relation. However, this connection is not clear yet for some weakly bound nuclear systems, especially for reactions induced by exotic radioactive nuclei. In this study, precise optical potentials of the halo nuclear system ${}^6\mathrm{He}+{}^{209}\mathrm{Bi}$ were extracted via ${}^{208}\mathrm{Pb}({}^7\mathrm{Li},{}^6\mathrm{He})$ transfer reactions with energies measured downward to the extremely sub-barrier region. The real potential presents a bell-like shape around the barrier as a normal threshold anomaly in tightly bound nuclear systems. However, the imaginary potential shows an abnormal behavior: it increases first with energy decreasing below the barrier and then falls quickly down to 0. It is the first time the threshold of the imaginary potential has been determined in an exotic nuclear system. Moreover, experimental results show the dispersion relation is not applicable for this system, which may be a common phenomenon for exotic nuclear systems. We discuss possible explanations for such a peculiar behavior, but further study is still desired for the underlying physics.