The nuclear equation of state (EOS) is explored with the constrained Hartree-Fock-Bogoliubov approach for self-conjugate nuclei. It is found that beyond a certain low, more or less universal density, those nuclei spontaneously cluster into $A/4$ $\alpha$ particles with $A$ the nucleon number. The energy at the threshold density increases linearly with the number of $\alpha$ particles as does the experimental threshold energy. Taking off the spurious c.m. energy of each $\alpha$ particle almost gives agreement between theory and experiment. The implications of these results with respect to $\alpha$ clustering and the nuclear EOS at low density are discussed.

Beta decay of ${}^{86}\mathrm{Ga}$ was studied by means of $\beta$-neutron-$\gamma$ spectroscopy. An isotopically pure ${}^{86}\mathrm{Ga}$ beam was produced at the Holifield Radioactive Ion Beam Facility using a resonance ionization laser ion source and high-resolution electromagnetic separation. The decay of ${}^{86}\mathrm{Ga}$ revealed a half-life of ${43}_{-15}^{+21}\mathrm{ms}$ and large $\beta$-delayed one-neutron and two-neutron branching ratios of $P_{1n}=60(10)\%$ and $P_{2n}=20(10)\%$. The $\beta \gamma$ decay of ${}^{86}\mathrm{Ga}$ populated a 527 keV transition that is interpreted as the deexcitation of the first $2^{+}$ state in the $N=54$ isotone ${}^{86}\mathrm{Ge}$ and suggests a quick onset of deformation in Ge isotopes beyond $N=50$.

We calculate the neutron-${}^{60}\mathrm{Ca}$ $S$-wave scattering phase shifts using state of the art coupled-cluster theory combined with modern ab initio interactions derived from chiral effective theory. Effects of three-nucleon forces are included schematically as density dependent nucleon-nucleon interactions. This information is combined with halo effective field theory in order to investigate the ${}^{60}\mathrm{Ca}$-neutron-neutron system. We predict correlations between different three-body observables and the two-neutron separation energy of ${}^{62}\mathrm{Ca}$. This provides evidence of Efimov physics along the calcium isotope chain. Experimental key observables that facilitate a test of our findings are discussed.

Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the standard model of particle physics. This Letter reports the results from phase I of the Germanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope ${}^{76}\mathrm{Ge}$. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kg yr. A blind analysis is performed. The background index is about $1\times {10}^{-2}\mathrm{counts}/(\mathrm{keV}\mathrm{kg}\mathrm{yr})$ after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of ${}^{76}\mathrm{Ge}$, $T_{1/2}^{0\nu }>2.1\times {10}^{25}\mathrm{yr}$ (90% C.L.). The combination with the results from the previous experiments with ${}^{76}\mathrm{Ge}$ yields $T_{1/2}^{0\nu }>3.0\times {10}^{25}\mathrm{yr}$ (90% C.L.).

We present a calculation of the giant dipole resonance in ${}^{16}\mathrm{O}$ based on a nucleon-nucleon ($NN$) interaction from chiral effective field theory that reproduces $NN$ scattering data with high accuracy. By merging the Lorentz integral transform and the coupled-cluster methods, we extend the previous theoretical limits for breakup observables in light nuclei with mass numbers ($A\le 7$) and address the collective giant dipole resonance of ${}^{16}\mathrm{O}$. We successfully benchmark the new approach against virtually exact results from the hyperspherical harmonics method in ${}^4\mathrm{He}$. Our results for ${}^{16}\mathrm{O}$ reproduce the position and the total strength (bremsstrahlung sum rule) of the dipole response very well. When compared to the cross section from photoabsorption experiments, the theoretical curve exhibits a smeared form of the peak. The tail region between 40 and 100 MeV is reproduced within uncertainties.

Collinear laser spectroscopy was performed on the nuclear ground states of the neutron-deficient isotopes ${}^{206,205,204}\mathrm{Fr}$. A new technique was developed to suppress hyperfine pumping in collinear laser spectroscopy of atoms. This involved high-frequency intensity modulation of narrow-linewidth laser light using fast-switching electro-optical modulators. The nuclear ground-state spins of ${}^{206,205,204}\mathrm{Fr}$ were determined to be 3, $9/2$, and 3, respectively. Both the changes in mean-squared charge radii and nuclear magnetic dipole moments indicate a departure from single-particle estimates.

Quark mass dependence of the equation of state (EOS) for nucleonic matter is investigated, on the basis of the Brueckner-Hartree-Fock method with the nucleon-nucleon interaction extracted from lattice QCD simulations. We observe saturation of nuclear matter at the lightest available quark mass corresponding to the pseudoscalar meson mass $\simeq 469\mathrm{MeV}$. Mass-radius relation of the neutron stars is also studied with the EOS for neutron-star matter from the same nuclear force in lattice QCD. We observe that the EOS becomes stiffer and thus the maximum mass of neutron star increases as the quark mass decreases toward the physical point.

We have carried out photodisintegration cross-section measurements on ${}^{86}\mathrm{Kr}$ using monoenergetic photon beams ranging from the neutron separation energy, $S_n=9.86\mathrm{MeV}$, to 13 MeV. We combine our experimental ${}^{86}\mathrm{Kr}(\gamma ,n){}^{85}\mathrm{Kr}$ cross section with results from our recent ${}^{86}\mathrm{Kr}(\gamma ,{\gamma }^{\prime })$ measurement below the neutron separation energy to obtain the complete nuclear dipole response of ${}^{86}\mathrm{Kr}$. The new experimental information is used to predict the neutron capture cross section of ${}^{85}\mathrm{Kr}$, an important branching point nucleus on the abundance flow path during $s$-process nucleosynthesis. Our new and more precise ${}^{85}\mathrm{Kr}(n,\gamma ){}^{86}\mathrm{Kr}$ cross section allows us to produce more precise predictions of the ${}^{86}\mathrm{Kr}$ abundance from $s$-process models. In particular, we find that the models of the $s$ process in asymptotic giant branch stars of mass $<1.5{\mathrm{M}}_{\odot }$, where the ${}^{13}\mathrm{C}$ neutron source burns convectively rather than radiatively, represent a possible solution for the highest ${}^{86}\mathrm{Kr}:{}^{82}\mathrm{Kr}$ ratios observed in meteoritic stardust SiC grains.

A high-resolution $\alpha$, x-ray, and $\gamma$-ray coincidence spectroscopy experiment was conducted at the GSI Helmholtzzentrum für Schwerionenforschung. Thirty correlated $\alpha$-decay chains were detected following the fusion-evaporation reaction ${}^{48}\mathrm{Ca}+{}^{243}\mathrm{Am}$. The observations are consistent with previous assignments of similar decay chains to originate from element $Z=115$. For the first time, precise spectroscopy allows the derivation of excitation schemes of isotopes along the decay chains starting with elements $Z>112$. Comprehensive Monte Carlo simulations accompany the data analysis. Nuclear structure models provide a first level interpretation.

Azimuthally anisotropic distributions of $D^0$, $D^{+}$, and $D^{*+}$ mesons were studied in the central rapidity region ($|y|<0.8$) in Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ per nucleon-nucleon collision, with the ALICE detector at the LHC. The second Fourier coefficient $v_2$ (commonly denoted elliptic flow) was measured in the centrality class 30%–50% as a function of the $D$ meson transverse momentum $p_T$, in the range $2–16\mathrm{GeV}/c$. The measured $v_2$ of $D$ mesons is comparable in magnitude to that of light-flavor hadrons. It is positive in the range $2<p_T<6\mathrm{GeV}/c$ with $5.7\sigma$ significance, based on the combination of statistical and systematic uncertainties.

An ab initio calculation of the ${}^{12}\mathrm{C}$ elastic form factor and sum rules of longitudinal and transverse response functions measured in inclusive ($e$, $e^{\prime }$) scattering are reported, based on realistic nuclear potentials and electromagnetic currents. The longitudinal elastic form factor and sum rule are found to be in satisfactory agreement with available experimental data. A direct comparison between theory and experiment is difficult for the transverse sum rule. However, it is shown that the calculated transverse sum rule has large contributions from two-body currents, indicating that these mechanisms lead to a significant enhancement of the quasielastic transverse response. This fact may have implications for the anomaly observed in recent neutrino quasielastic charge-changing scattering experiments on ${}^{12}\mathrm{C}$.

Appropriate combinations of up to fourth order cumulants of net strangeness fluctuations and their correlations with net baryon number and electric charge fluctuations, obtained from lattice QCD calculations, have been used to probe the strangeness carrying degrees of freedom at high temperatures. For temperatures up to the chiral crossover, separate contributions of strange mesons and baryons can be well described by an uncorrelated gas of hadrons. Such a description breaks down in the chiral crossover region, suggesting that the deconfinement of strangeness takes place at the chiral crossover. On the other hand, the strangeness carrying degrees of freedom inside the quark gluon plasma can be described by a weakly interacting gas of quarks only for temperatures larger than twice the chiral crossover temperature. In the intermediate temperature window, these observables show considerably richer structures, indicative of the strongly interacting nature of the quark gluon plasma.

We study particle production in ultrarelativistic nuclear collisions at CERN SPS and LHC energies and the conditions of chemical freeze-out. We determine the effect of the inelastic reactions between hadrons occurring after hadronization and before chemical freeze-out employing the ultrarelativistic quantum molecular dynamics hybrid model. The differences between the initial and the final hadronic multiplicities after the rescattering stage resemble the pattern of data deviation from the statistical equilibrium calculations. By taking these differences into account in the statistical model analysis of the data, we are able to reconstruct the original hadrochemical equilibrium points in the ($T$, ${\mu }_B$) plane which significantly differ from chemical freeze-out ones and closely follow the parton-hadron phase boundary recently predicted by lattice quantum chromodynamics.

We report on parity-violating asymmetries in the nucleon resonance region measured using inclusive inelastic scattering of 5–6 GeV longitudinally polarized electrons off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the $\Delta (1232)$. They provide a verification of quark-hadron duality—the equivalence of the quark- and hadron-based pictures of the nucleon—at the (10–15)% level in this electroweak observable, which is dominated by contributions from the nucleon electroweak $\gamma Z$ interference structure functions. In addition, the results provide constraints on nucleon resonance models relevant for calculating background corrections to elastic parity-violating electron scattering measurements.

The plasma astrophysical $S$ factor for the ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ fusion reaction was measured for the first time at temperatures of few keV, using the interaction of intense ultrafast laser pulses with molecular deuterium clusters mixed with ${}^3\mathrm{He}$ atoms. Different proportions of ${\mathrm{D}}_2$ and ${}^3\mathrm{He}$ or ${\mathrm{CD}}_4$ and ${}^3\mathrm{He}$ were mixed in the gas target in order to allow the measurement of the cross section for the ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ reaction. The yield of 14.7 MeV protons from the ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ reaction was measured in order to extract the astrophysical $S$ factor at low energies. Our result is in agreement with other $S$ factor parametrizations found in the literature.

We propose an extension of the continuum discretized coupled channels (CDCC) method, where the projectile is described by a microscopic cluster model. This microscopic generalization (MCDCC) relies only on nucleon-target interactions, and therefore presents an important predictive power. Core excitations can be included without any further parameter. As an example, we investigate the ${}^7\mathrm{Li}+{}^{208}\mathrm{Pb}$ elastic scattering at $E_{\mathrm{lab}}=27$ and 35 MeV. The ${}^7\mathrm{Li}$ nucleus is known to present an $\alpha +t$ cluster structure, and is well described by the resonating group method. An excellent agreement is obtained for the ${}^7\mathrm{Li}+{}^{208}\mathrm{Pb}$ elastic cross sections, provided that breakup channels are properly included. We also present an application to inelastic scattering and discuss future applications of the MCDCC.

The first spectroscopy of excited states in ${}^{52}\mathrm{Ni}$ ($T_z=-2$) and ${}^{51}\mathrm{Co}$ ($T_z=-3/2$) has been obtained using the highly selective two-neutron knockout reaction. Mirror energy differences between isobaric analogue states in these nuclei and their mirror partners are interpreted in terms of isospin nonconserving effects. A comparison between large-scale shell-model calculations and data provides the most compelling evidence to date that both electromagnetic and an additional isospin nonconserving interactions for $J=2$ couplings, of unknown origin, are required to obtain good agreement.

An earlier measurement on the $4^{+}$ to $2^{+}$ radiative transition in ${}^8\mathrm{Be}$ provided the first electromagnetic signature of its dumbbell-like shape. However, the large uncertainty in the measured cross section does not allow a stringent test of nuclear structure models. This Letter reports a more elaborate and precise measurement for this transition, via the radiative capture in the ${}^4\mathrm{He}+{}^4\mathrm{He}$ reaction, improving the accuracy by about a factor of 3. Ab initio calculations of the radiative transition strength with improved three-nucleon forces are also presented. The experimental results are compared with the predictions of the alpha cluster model and ab initio calculations.

We extend the formalism of self-consistent Green’s function theory to include three-body interactions and apply it to isotopic chains around oxygen for the first time. The third-order algebraic diagrammatic construction equations for two-body Hamiltonians can be exploited upon defining system-dependent one- and two-body interactions coming from the three-body force, and, correspondingly, dropping interaction-reducible diagrams. The Koltun sum rule for the total binding energy acquires a correction due to the added three-body interaction. This formalism is then applied to study chiral two- and three-nucleon forces evolved to low momentum cutoffs. The binding energies of nitrogen, oxygen, and fluorine isotopes are reproduced with good accuracy and demonstrate the predictive power of this approach. Leading order three-nucleon forces consistently bring results close to the experiment for all neutron rich isotopes considered and reproduce the correct driplines for oxygen and nitrogen. The formalism introduced also allows us to calculate form factors for nucleon transfer on doubly magic systems.

Two puzzling features in the experimental study of jet quenching in central $\mathrm{Pb}+\mathrm{Pb}$ collisions at the LHC are explained within a linearized Boltzmann transport model for jet propagation. A $\gamma$-tagged jet is found to lose about 15% of its initial energy while its azimuthal angle remains almost unchanged due to rapid cooling of the medium. The reconstructed jet fragmentation function is found to have some modest enhancement at both small and large fractional momenta as compared to that in the vacuum because of the increased contribution of leading particles to the reconstructed jet energy and induced gluon radiation and recoiled partons. A $\gamma$-tagged jet fragmentation function is proposed that is more sensitive to jet-medium interaction and the jet transport parameter in the medium. The effects of recoiled medium partons on the reconstructed jets are also discussed.