In most of the successful versions of covariant density functional theory in nuclei, the Fock terms are not included explicitly, which leads to local functionals and forms the basis of their widespread applicability at present. However, it has serious consequences for the description of Gamow-Teller resonances (GTR) and spin-dipole resonances (SDR) which can only be cured by adding further phenomenological parameters. Relativistic Hartree-Fock models do not suffer from these problems. They can successfully describe the GTR and SDR as well as the isovector part of the Dirac effective mass without any additional parameters. However, they are nonlocal and require considerable numerical effort. By the zero-range reduction and the Fierz transformation, a new method is proposed to take into account the Fock terms in local functionals, which retains the simplicity of conventional models and provides proper descriptions of the spin-isospin channels and the Dirac masses.

We present limits on Majoron-emitting neutrinoless double-$\beta$ decay modes based on an exposure of 112.3 days with 125 kg of ${}^{136}$Xe. In particular, a lower limit on the ordinary (spectral index $n=1$) Majoron-emitting decay half-life of ${}^{136}$Xe is obtained as $T_{1/2}^{0\nu {\chi }^0}>2.6\times {10}^{24}$ yr at 90$\%$ C.L., a factor of five more stringent than previous limits. The corresponding upper limit on the effective Majoron-neutrino coupling, using a range of available nuclear matrix calculations, is $\langle g_{ee}\rangle <(0.8–1.6)\times {10}^{-5}$. This excludes a previously unconstrained region of parameter space and strongly limits the possible contribution of ordinary Majoron emission modes to $0\nu \beta \beta$ decay for neutrino masses in the inverted hierarchy scheme.

Background: Following the 2007 precise measurements of monopole strengths in tin isotopes, there has been a continuous theoretical effort to obtain a precise description of the experimental results. Up to now, there is no satisfactory explanation of why the tin nuclei appear to be significantly softer than ${}^{208}$Pb.

Purpose: We determine the influence of finite-range and separable pairing interactions on monopole strength functions in semimagic nuclei.

Methods: We employ self-consistently the quasiparticle random phase approximation on top of spherical Hartree-Fock-Bogoliubov solutions. We use the Arnoldi method to solve the linear-response problem with pairing.

Results: We found that the difference between centroids of giant monopole resonances measured in lead and tin (about 1 MeV) always turns out to be overestimated by about 100$\%$. We also found that the volume incompressibility, obtained by adjusting the liquid-drop expression to microscopic results, is significantly larger than the infinite-matter incompressibility.

Conclusions: The zero-range and separable pairing forces cannot induce modifications of monopole strength functions in tin to match experimental data.

The production of hadrons in heavy-ion collisions at the Relativistic Heavy-Ion Collider in the low-transverse-momentum ($p_T$) region is investigated in the recombination model with emphasis on the effects of minijets on the azimuthal anisotropy. Since the study is mainly focused on the hadronization of partons at late time, the fluid picture is not used to trace the evolution of the system. The inclusive distributions at low $p_T$ are determined as the recombination products of thermal partons. The $p_T$ dependencies of both the pion and the proton have a common exponential factor apart from other dissimilar kinematic and resonance factors, because they are inherited from the same pool of thermal partons. Instead of the usual description based on hydrodynamics, the azimuthal anisotropy of the produced hadrons is explained as the consequence of the effects of minijets, either indirectly through the recombination of enhanced thermal partons in the vicinity of the trajectories of the semihard partons or directly through thermal-shower recombination. Although our investigation is focused on the single-particle distribution at midrapidity, we give reasons why a component in that distribution can be identified with the ridge, which, together with the second harmonic $v_2$, is due to the semihard partons created near the medium surface that lead to calculable anisotropy in $\phi$. It is shown that the higher azimuthal harmonics, $v_n$, can also be well reproduced without reference to flow. The $p_T$ and centrality dependencies of the higher harmonics are prescribed by the interplay between thermal-thermal (TT) and thermal-shower (TS) recombination components. The implication of the success of this drastic departure from the conventional approach is discussed.

The centrality dependence of charged-hadron production in relativistic heavy-ion collisions at CERN Large Hadron Collider (LHC) energies is investigated in a nonequilibrium-statistical relativistic diffusion model (RDM) with three sources. Theoretical pseudorapidity distributions are compared with preliminary PbPb ALICE data at LHC energy of $\sqrt{s_{NN}}$ $=$ 2.76 TeV for seven centralities, and a previous RDM prediction for this energy is confronted with the data. Refined predictions for 5.52 TeV PbPb based on RDM parameter extrapolations are presented.

Recent data on the nuclear modification factor $R_{AA}$ of jet fragments in $2.76$ ATeV Pb+Pb collisions at the Large Hadron Collider (LHC) indicate that the jet-medium coupling in a quark-gluon plasma (QGP) is reduced at LHC energies and not compatible with the coupling deduced from data at the Relativistic Hadron Collider (RHIC). We estimate the reduction factor from a combined fit to the available data on $R_{AA}(\sqrt{s},p_T,b)$ and the elliptic flow $v_2(\sqrt{s},p_T,b)$ at $\sqrt{s}=0.2,2.76$ ATeV over a transverse momentum range $p_T\sim 10–100$ GeV and a broad impact parameter, $b$, range. We use a simple analytic “polytrope” model ($dE/dx=-\kappa E^a{x}^z{T}^c$) to investigate the dynamical jet-energy loss model dependence. Varying $a=0–1$ interpolates between weakly coupled and strongly coupled models of jet-energy dependence while $z=0–2$ covers a wide range of possible jet-path dependencies from elastic and radiative to holographic string mechanisms. Our fit to LHC data indicates an approximate 40$\%$ reduction of the coupling $\kappa$ from RHIC to LHC and excludes energy-loss models characterized by a jet-energy exponent with $a>1/3$. In particular, the rapid rise of $R_{AA}$ with $p_T\ge 10$ GeV combined with the slow variation of the asymptotic $v_2\left(p_T\right)$ at the LHC rules out popular exponential geometric optics models ($a=1$). The LHC data are compatible with $0\le a\le 1/3$ pQCD-like energy-loss models where the jet-medium coupling is reduced by approximately 10$\%$ between RHIC and LHC.

The two-neutrino ($2\nu 2\beta$) and neutrinoless ($0\nu 2\beta$) double-$\beta$ decays of ${}^{96}$Ru are investigated for the transitions to the ground state, $0_{\mathrm{gs}}^{+}$, and $0^{+}$ and $2^{+}$ excited states in ${}^{96}$Mo by using the quasiparticle random-phase approximation combined with the multiple-commutator model. $G$-matrix-based nuclear forces are used in realistic single-particle model spaces. All the possible channels, ${\beta }^{+}{\beta }^{+}$, ${\beta }^{+}$EC, and ECEC, are discussed for both the $2\nu 2\beta$ and $0\nu 2\beta$ decays. The associated half-lives are computed, in particular the one corresponding to the resonant neutrinoless double electron capture (R$0\nu$ECEC) transition to the $2.712.68\text{-MeV}$ nuclear state in ${}^{96}$Mo. This work represents the most complete theoretical investigation of the double-$\beta$-decay properties of ${}^{96}$Ru thus far.

The specific shear viscosity $\overline{\eta }$ of a classically rotating system of nucleons that interact via a monopole pairing force is calculated including the effects of thermal fluctuations and coupling to pair vibrations within the self-consistent quasiparticle random-phase approximation. It is found that $\overline{\eta }$ increases with angular momentum $M$ at a given temperature $T$. In medium and heavy systems, $\overline{\eta }$ decreases with increasing $T$ at $T⩾2$ MeV and this feature is not affected much by angular momentum. However, in lighter systems (with the mass number $A⩽20$), $\overline{\eta }$ increases with $T$ at a value of $M$ close to the maximal value $M_{\text{max}}$, which is defined as the limiting angular momentum for each system. The values of $\overline{\eta }$ obtained within the schematic model as well as for systems with realistic single-particle energies are always larger than the universal lower-bound conjecture $\hslash /\left(4\pi k_B\right)$ up to $T=5$ MeV.

Quasiparticle random-phase approximation (QRPA) is applied to two nuclei, and the overlap of the QRPA excited states based on the different nuclei is calculated. The aim is to calculate the overlap of intermediate nuclear states of the double-$\beta$ decay. We use the like-particle QRPA after the closure approximation is applied to the nuclear matrix elements. The overlap is calculated rigorously by making use of the explicit equation of the QRPA ground state. The formulation of the overlap is shown, and a test calculation is performed. The effectiveness of the truncations used is shown.

Continuing our effort to build a consistent power counting for chiral nuclear effective field theory (EFT), we discuss the subleading contact interactions, or counterterms, in the singlet channels of nucleon-nucleon scattering, with renormalization group invariance as the constraint. We argue that the rather large cutoff error of the leading amplitude requires $\mathcal{O}\left(Q\right)$ of the EFT expansion to be nonvanishing, contrary to Weinberg's original power counting. This, together with the ultraviolet divergences of two-pion exchanges in the distorted-wave expansion, leads to enhancement of the ${}^1{S}_0$ counterterms and results in a pionless-theory-like power counting for the singlet channels.

The level structure of ${}^{18}$Ne above the $\alpha$-decay threshold has been studied using the ${}^{16}$O(${}^3$He,$n$) reaction. A coincidence measurement of neutrons and charged particles decaying from populated states in ${}^{18}$Ne has been made. Decay branching ratios were measured for six resonances and used to calculate the ${}^{14}$O($\alpha$,$p$)${}^{17}$F reaction rate which is a measure of one of two breakout paths from the hot CNO cycle. The new experimental information combined with previous experimental and theoretical information provides a more accurate calculation of the reaction rate.

Previous to the present study, three isolated rotational bands with tentative spin assignments had been reported in the literature and the authors estimated that, to meet the predicted alignments, the spin of these bands has to be increased by $4\hslash$ to 5$\hslash$. Based on the linking transitions observed in the present work, through the reaction ${}^{118}$Sn(${}^{14}$N,4n)${}^{128}$La, and the $I^{\pi }=5^{+}$ assignment for the bandhead of the yrast band proposed by Hayakawa, Lu, Mukai, Saitoh, Hasimoto, Komatsubara, and Furuno [Z. Phys. A 352, 241 (1995)] from $\beta$-decay studies, the spins of these bands are reassigned. The alignments of bands in ${}^{128}$La deduced from the present spin assignments are consistent with the alignments of relevant bands observed in neighboring odd-$A$ nuclei ${}^{127}$La, ${}^{127}$Ba, and ${}^{131}$La. Additionally, a new band with a tentative configuration assignment $\pi h_{11/2}\otimes d_{3/2}$ is reported.

The high-spin decay of ${}^{71}$Se was studied using the ${}^{54}$Fe${(}^{23}$Na,$\alpha pn)$ reaction at 80 MeV and the Florida State University Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. Based on prompt $\gamma$-$\gamma$ coincidences measured in the experiment, the known level scheme was enhanced and extended to higher spin with 19 new transitions. A band that was previously suggested to have positive parity was reassigned as the “missing” signature partner of an existing negative-parity band. Spins were assigned based on directional correlation of oriented nuclei ratios. Lifetimes of 17 excited states were measured using the Doppler-shift attenuation method. Experimental $Q_t$ values imply an intermediate degree of collective behavior for ${}^{71}$Se at high spin. Theoretical $Q_t$ values determined from cranked Woods-Saxon (CWS) calculations show better agreement with the experimental ones for the positive-parity states than the negative-parity states. Shape competition and $\gamma$ softness characterize the low-spin states of the lowest positive- and negative-parity bands based on the CWS calculations. At high spin, triaxial shapes with $\gamma >0^{\circ }$ are predicted.

The ${}^{28}\text{Si}{\left(p{,}^3\text{He}\right)}^{26}\text{Al}$ reaction was utilized for the first time to study the levels in ${}^{26}$Al, using a proton beam from the Holifield Radioactive Ion Beam Facility. Five previously unreported states in ${}^{26}$Al are observed and discussed, including Distorted Wave Born Approximation analysis. Proton-decay branching ratios consistent with previous studies and theoretical expectations were found by detecting decay protons from highly excited ${}^{26}$Al states in coincidence with the ${}^3$He particles.

We address the issue of unbiased model selection and propose a methodology based on Bayesian inference to extract physical information from kaon photoproduction $\gamma p\to K^{+}\Lambda$ data. We use the single-channel Regge-plus-resonance (RPR) framework for $\gamma p\to K^{+}\Lambda$ to illustrate the proposed strategy. The Bayesian evidence $\mathcal{Z}$ is a quantitative measure for the model's fitness given the world's data. We present a numerical method for performing the multidimensional integrals in the expression for the Bayesian evidence. We use the $\gamma p\to K^{+}\Lambda$ data with an invariant energy $W>2.6$ GeV in order to constrain the background contributions in the RPR framework with Bayesian inference. Next, the resonance information is extracted from the analysis of differential cross sections and single- and double-polarization observables. This background and resonance content constitutes the basis of a model, which is coined RPR-2011. It is shown that RPR-2011 yields a comprehensive account of the kaon photoproduction data and provides reasonable predictions for $e+p\to e^{\prime }+K^{+}+\Lambda$ observables.

Final-state interaction (FSI) effects are discussed in the context of Monte Carlo simulations of neutrino-nucleus interactions. A role of formation time is explained and several models describing this effect are compared. Various observables which are sensitive to FSI effects are reviewed including pion-nucleus interaction and hadron yields in backward hemisphere. NuWro Monte Carlo neutrino event generator is described and its ability to understand neutral current ${\pi }^0$ production data in $\sim 1$ GeV neutrino flux experiments is demonstrated.

Background: Theoretical calculations of the four-body scattering above the four-body breakup threshold are technically very difficult owing to complicated singularities in the momentum space or boundary conditions in the coordinate space.

Purpose: We aim at calculating the neutron-${}^3$H scattering observables above the four-nucleon breakup threshold.

Methods: We employ Alt, Grassberger, and Sandhas (AGS) integral equations for the four-nucleon transition operators and solve them in the momentum-space framework using the complex-energy method. We significantly improve its accuracy and practical applicability by introducing the numerical integration method with the special weights.

Results: Using realistic nuclear interaction models we obtain fully converged results for the neutron-${}^3$H scattering. Elastic differential cross section and neutron analyzing power as well as the total cross section are calculated at 14.1, 18.0, and 22.1 MeV neutron energy.

Conclusions: Realistic four-nucleon scattering calculations above the four-nucleon breakup threshold are feasible. There is quite good agreement between the theoretical predictions and experimental data for the neutron-${}^3$H scattering in the considered energy regime.

Existing ${}^{10}$Be($d$,$t$)${}^9$Be neutron pickup data are analyzed using the same bound-state form factors for the ${\langle }^{10}\mathrm{Be}{|}^9\mathrm{Be}+n\rangle$ overlap as in a recent analysis of single-neutron knockout [Grinyer et al.,  Phys. Rev. Lett. 106, 162502 (2011)]. While the knockout data were well described by a bound-state form factor calculated using the variational Monte Carlo (VMC) technique, including an appropriate neutron binding potential, the ${}^{10}$Be($d$,$t$)${}^9$Be pickup data are significantly overpredicted using this form factor. In addition, the no-core shell model (NCSM) and VMC form factors yield the same calculated pickup cross sections whereas the knockout results using these form factors differed by 20$\%$. We explore possible sources of ambiguity in the pickup calculations that affect our ability to compare the absolute magnitudes in cross sections between these two very different reactions.

We study the influence of a temperature-dependent shear viscosity over entropy density ratio $\eta /s$, different shear relaxation times ${\tau }_{\pi }$, as well as different initial conditions on the transverse momentum spectra of charged hadrons and identified particles. We investigate the azimuthal flow asymmetries as a function of both collision energy and centrality. The elliptic flow coefficient turns out to be dominated by the hadronic viscosity at RHIC energies. Only at higher collision energies the impact of the viscosity in the QGP phase is visible in the flow asymmetries. Nevertheless, the shear viscosity near the QCD transition region has the largest impact on the collective flow of the system. We also find that the centrality dependence of the elliptic flow is sensitive to the temperature dependence of $\eta /s$.

We present a model for describing nuclear matter at finite density based on quarks interacting with chiral fields $\sigma$ and $\pi$ and with vector mesons introduced as massive gauge fields. The chiral Lagrangian includes a logarithmic potential, associated with the breaking of scale invariance. We provide results for the soliton in vacuum and at finite density, using the Wigner-Seitz approximation. We show that the model can reach higher densities with respect to the linear $\sigma$ model, and that the introduction of vector mesons allows us to obtain saturation.