The linear-chain states of ${}^{14}\mathrm{C}$ are theoretically investigated by using the antisymmetrized molecular dynamics. The calculated excitation energies and the $\alpha$ decay widths of the linear-chain states were compared with the observed data reported by recent experiments. The properties of the positive-parity linear-chain states reasonably agree with the observation, which convinces us of the linear-chain formation in the positive-parity states. On the other hand, in the negative-parity states, it is found that the linear-chain configuration does not correspond to a single eigenstate but is mixed with other configurations in the eigenstates and does not form a single rotational band. As a further evidence of the linear-chain formation, we focus on the $\alpha$-decay pattern. It is shown that the linear-chain states decay to the excited states of daughter nucleus ${}^{10}\mathrm{Be}$ as well as to the ground state, while other cluster states dominantly decay into the ground state. Hence, we regard that this characteristic decay pattern is a strong signature of linear-chain formation.

The dipole strength distribution of ${}^{80}\mathrm{Se}$ was studied in a photon-scattering experiment by using bremsstrahlung produced with an electron beam of energy 11.5 MeV at the linear accelerator ELBE. We identified $180\gamma$ transitions up to an energy of 9.6 MeV, and analyzed the strength in the quasicontinuum of the spectrum. Simulations of statistical $\gamma$-ray cascades were performed to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section below the neutron-separation energy derived in this way was combined with the photoabsorption cross section obtained from an earlier $(\gamma ,n)$ experiment and used as an input for the calculation of ${}^{79}\mathrm{Se}(n,\gamma )$ reaction rates on the basis of the statistical reaction model.

A previous simple parametrization of mirror energy differences in pairs of nuclei consisting of a $p$-shell core plus two $sd$-shell nucleons is applied to a series of mirrors that contain $sd$-shell nucleons in the core. Results for ${}^{19,20}\mathrm{Mg}$ agree with experiment and with a potential model. Predictions are made for $2p$ separation energies of ${}^{17,18}\mathrm{Mg}$.

Following the recent success of anisotropic hydrodynamics, I propose here a new, general prescription for the hydrodynamic expansion around an anisotropic background. The anisotropic distribution fixes exactly the complete energy-momentum tensor, just like the effective temperature fixes the proper energy density in the ordinary expansion around local equilibrium. This means that momentum anisotropies are already included at the leading order, allowing for large pressure anisotropies without the need of a next-to-leading-order treatment. The first moment of the Boltzmann equation (local four-momentum conservation) provides the time evolution of the proper energy density and the four-velocity. Differently from previous prescriptions, the dynamic equations for the pressure corrections are not derived from the zeroth or second moment of the Boltzmann equation, but they are taken directly from the exact evolution given by the Boltzmann equation. As known in the literature, the exact evolution of the pressure corrections involves higher moments of the Boltzmann distribution, which cannot be fixed by the anisotropic distribution alone. Neglecting the next-to-leading-order contributions corresponds to an approximation, which depends on the chosen form of the anisotropic distribution. I check the the effectiveness of the leading-order expansion around the generalized Romatschke-Stricklad distribution, comparing with the exact solution of the Boltzmann equation in the Bjorken limit with the collisional kernel treated in the relaxation-time approximation, finding an unprecedented agreement.

Background: Accelerator-based neutrino oscillation measurements depend on observing a difference between the expected and measured rate of neutrino-nucleus interactions at different neutrino energies or different distances from the neutrino source. Neutrino-nucleus scattering cross sections are complicated and depend on the neutrino beam energy, the neutrino-nucleus interaction, and the structure of the nucleus. Knowledge of the incident neutrino energy spectrum and neutrino-detector interactions are crucial for analyzing neutrino oscillation experiments. The ArgoNeut liquid argon time projection chamber (lArTPC) observed charged-current neutrino-argon scattering events with two protons back-to-back in the final state (“hammer” events) which they associated with short-range correlated (SRC) nucleon-nucleon pairs. The large volume MicroBooNE lArTPC will measure far more of these unique events.

Purpose: Determine what we can learn about the incident neutrino energy spectrum and/or the structure of SRC from hammer events that will be measured in MicroBooNE.

Methods: We simulate hammer events using two models and the well-known electron-nucleon scattering cross section. In the first model the neutrino (or electron) scatters from a moving proton, ejecting a ${\pi }^{+}$, and the ${\pi }^{+}$ is then absorbed on a moving deuteron-like $np$ pair. In the second model the neutrino (or electron) scatters from a moving nucleon, exciting it to a $\mathrm{\Delta }$ or $N^{*}$, which then de-excites by interacting with a second nucleon: $\mathrm{\Delta }N\to pp$.

Results: The pion production and reabsorption process results in two back-to-back protons each with momentum of about 500 MeV/$c$, very similar to that of the observed ArgoNeut events. These distributions are insensitive to either the relative or center-of-mass momentum of the $np$ pair that absorbed the $\pi$. In this model, the incident neutrino energy can be reconstructed relatively accurately using the outgoing lepton. The $\mathrm{\Delta }p\to pp$ process results in two protons that are less similar to the observed events.

Conclusions: ArgoNeut hammer events can be described by a simple pion production and reabsorption model. The hammer events that will be measured in MicroBooNE can be used to determine the incident neutrino energy but not to learn about SRC. We suggest that this reaction channel could be used for neutrino oscillation experiments to complement other channels with higher statistics but different systematic uncertainties.

We study the spin-flavor structure of the nucleon's chiral-odd generalized parton distributions (transversity GPDs) in the large-$N_c$ limit of QCD. In contrast to the chiral-even case, only three combinations of the four chiral-odd GPDs are nonzero in the leading order of the $1/N_c$ expansion: ${\overline{E}}_T=E_T+2{\tilde{H}}_T,H_T$, and ${\tilde{E}}_T$. The degeneracy is explained by the absence of spin-orbit interactions correlating the transverse momentum transfer with the transverse quark spin. It can also be deduced from the natural $N_c$ scaling of the quark-nucleon helicity amplitudes associated with the GPDs. In the GPD ${\overline{E}}_T$ the flavor-singlet component $u+d$ is leading in the $1/N_c$ expansion, while in $H_T$ and ${\tilde{E}}_T$ it is the flavor-nonsinglet components $u-d$. The large-$N_c$ relations are consistent with the spin-flavor structure extracted from hard exclusive ${\pi }^0$ and $\eta$ electroproduction data, if it is assumed that the processes are mediated by twist-3 amplitudes involving the chiral-odd GPDs and the chiral-odd pseudoscalar meson distribution amplitudes.

Prompt neutron multiplicity distributions ν($A$) are generally required for prompt emission correction of double energy ($2E$) measurements of fission fragments in order to determine pre-neutron fragment properties. The lack of experimental ν($A$) data especially at higher incident neutron energy imposes the use of prompt emission models to predict ν($A$). At incident neutron energies ($\mathit{En}$) where multiple fission chances are involved, the Point-by-Point (PbP) model of prompt emission is able to provide the individual ν($A$) of the compound nuclei of the main and secondary nucleus chains that are undergoing fission at a given $\mathit{En}$. The total ν($A$) are obtained by averaging these individual ν($A$) over the fission chance probabilities (expressed as total and partial fission cross-section ratios). An indirect validation of the total ν($A$) results is proposed. At high $\mathit{En}$ (above 70 MeV) the PbP results of individual ν($A$) of the first few nuclei of the main and secondary nucleus chains exhibit an almost linear increase. This shape is explained by the damping of shell effects entering the superfluid expression of the level-density parameters. They tend to approach the asymptotic values for a great part of the fragments. This fact leads to a smooth and almost linear increase of fragment excitation energy with the fragment mass number that is reflected in a smooth and almost linear behavior of individual ν($A$). The comparison of the present results with those of the GEF code reveals different shapes of ν($A$) as well as different total average neutron multiplicity as a function of the $\mathit{En}$. At high $\mathit{En}$ the PbP calculations definitely reflect the influence of the almost linear shape of individual ν($A$) of the first few nuclei of the U and Pa chains. The differences between the total ν($A$) obtained by averaging the PbP results of individual ν($A$) over fission cross-section ratios of different evaluations are insignificant.

We present a detailed QCD analysis of nucleon structure functions $x{F}_3(x,Q^2)$, based on Laplace transforms and the Jacobi polynomials approach. The analysis corresponds to the next-to-leading order and next-to-next-to-leading order approximations of perturbative QCD. The Laplace transform technique, as an exact analytical solution, is used for the solution of nonsinglet Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations at low- and large-$x$ values. The extracted results are used as input to obtain the $x$ and $Q^2$ evolution of $x{F}_3(x,Q^2)$ structure functions using the Jacobi polynomials approach. In our work, the values of the typical QCD scale ${\mathrm{\Lambda }}_{\overline{\mathrm{MS}}}^{\left(n_f\right)}$ and the strong coupling constant ${\alpha }_s\left(M_Z^2\right)$ are determined for four quark flavors ($n_f=4$) as well. A careful estimation of the uncertainties shall be performed using the Hessian method for the valence-quark distributions, originating from the experimental errors. We compare our valence-quark parton distribution functions sets with those of other collaborations, in particular with the CT14, MMHT14, and NNPDF sets, which are contemporary with the present analysis. The obtained results from the analysis are in good agreement with those from the literature.

A two-dimensional collective Hamiltonian (2DCH) on both azimuth and polar motions in triaxial nuclei is proposed to investigate the chiral and wobbling modes. In the 2DCH, the collective potential and the mass parameters are determined from three-dimensional tilted axis cranking (TAC) calculations. The broken chiral and signature symmetries in the TAC solutions are restored by the 2DCH. The validity of the 2DCH is illustrated with a triaxial rotor ($\gamma =-{30}^{\circ }$) coupling to one $h_{11/2}$ proton particle and one $h_{11/2}$ neutron hole. By diagonalizing the 2DCH, the angular momenta and energy spectra are obtained. These results agree with the exact solutions of the particle rotor model (PRM) at high rotational frequencies. However, at low frequencies, the energies given by the 2DCH are larger than those by the PRM due to the underestimation of the mass parameters. In addition, with increasing angular momentum, the transitions from the chiral vibration to chiral rotation and further to longitudinal wobbling motion have been presented in the 2DCH.

The lifetime $\tau \left(0_2^{+}\right)$ of ${}^{152}\mathrm{Gd}$ has been measured using fast electronic scintillation timing (FEST) with an array of high-purity germanium (HPGe) and cerium-doped lanthanum bromide (${\mathrm{LaBr}}_3$) detectors. ${}^{152}\mathrm{Gd}$ was produced via an $(\alpha ,n)$ reaction on a gold backed ${}^{149}\mathrm{Sm}$ target. The measured lifetime of $\tau \left(0_2^{+}\right)=96\left(6\right)\mathrm{ps}$ corresponds to a reduced transition strength of $B(E2;0_2^{+}\to 2_1^{+})=111\left(7\right)$ W.u. and an $E0$ transition strength of ${\rho }^2\left(E0\right)=39\left(3\right)\times {10}^{-3}$ to the ground state. This result provides experimental support for the validity of a correlation that would be a novel indicator for a quantum phase transition (QPT).

We report the excitation energy dependence of specific heat ($c_v$) of hadronic matter at freeze-out in Au+Au and Cu+Cu collisions at the BNL Relativistic Heavy Ion Collider energies by analyzing the published data on event-by-event mean transverse momentum ($\langle p_T\rangle$) distributions. The $\langle p_T\rangle$ distributions in finite $p_T$ ranges are converted to distributions of effective temperatures, and dynamical fluctuations in temperature are extracted by subtracting widths of the corresponding mixed event distributions. The heat capacity per particle at the kinetic freeze-out surface is presented as a function of collision energy, which shows a sharp rise in $c_v$ below $\sqrt{s_{NN}}=62.4$ GeV. We employ the hadron resonance gas (HRG) model to estimate $c_v$ at the chemical and kinetic freeze-out surfaces. The experimental results are compared to the HRG and other theoretical model calculations. HRG results show good agreement with data. Model predictions for $c_v$ at the CERN Large Hadron Collider energy are presented.

The forward-emitted low energy tail of the neutron spectrum generated by the ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$ reaction on a thick target at a proton energy of 1893.6 keV was measured by time-of-flight spectroscopy. The measurement was performed at BELINA (Beam Line for Nuclear Astrophysics) of the Laboratori Nazionali di Legnaro. Using the reaction kinematics and the proton on lithium stopping power the shape of the excitation function is calculated from the measured neutron spectrum. Good agreement with two reported measurements was found. Our data, along with the previous measurements, are well reproduced by the Breit-Wigner single-resonance formula for $s$-wave particles. The differential yield of the reaction is calculated and the widely used neutron spectrum at a proton energy of 1912 keV was reproduced. Possible causes regarding part of the 6.5% discrepancy between the ${}^{197}\mathrm{Au}(n,\gamma )$ cross section measured at this energy by Ratynski and Kappeler [Phys. Rev. C 37, 595 (1988)] and the one obtained using the Evaluated Nuclear Data File version B-VII.1 are given.

We show the importance of separated efficiency corrections between positively and negatively charged particles for cumulant calculations by toy models and analytical calculations. Our results indicate that $S\sigma$ in published net-proton results from the STAR experiment will be suppressed about 10% in central collisions and 20% in peripheral collisions at the beam energy of $\sqrt{s_{NN}}=200\mathrm{GeV}$ if the separated efficiencies are used to perform the efficiency correction, while no sizable efffect can be seen for $\kappa {\sigma }^2$.

New results for electric dipole strength in the chain of even-even calcium isotopes with the mass numbers $A=40–54$ are presented. Starting from the covariant Lagrangian of quantum hadrodynamics, spectra of collective vibrations (phonons) and phonon-nucleon coupling vertices for $J\le 6$ and natural parity were computed in a self-consistent relativistic quasiparticle random-phase approximation (RQRPA). These vibrations coupled to Bogoliubov two-quasiparticle configurations $\left(2\mathrm{q}\otimes \mathrm{phonon}\right)$ formed the model space for the calculations of the dipole response function in the relativistic quasiparticle time blocking approximation. The calculations in the latter approach were performed for the giant dipole resonance (GDR) and compared to those obtained with the RQRPA and to available data. The evolution of the dipole strength with the neutron number is investigated for both high-frequency GDRs and low-lying strengths. The development of a pygmy resonant structure on the low-energy shoulder of the GDR is traced and analyzed in terms of transition densities. A dependence of the pygmy dipole strength on the isospin asymmetry parameter is extracted.

${}^{136}\mathrm{Xe}$ is a $0\nu \beta \beta$ decay candidate isotope, and is used in multiple experiments searching for this hypothetical decay mode. These experiments require precise information about neutron capture for their background characterization and minimization. Thermal and resonant neutron capture on ${}^{136}\mathrm{Xe}$ have been measured at the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center. A neutron beam ranging from thermal energy to greater than 100 keV was incident on a gas cell filled with isotopically pure ${}^{136}\mathrm{Xe}$. The relative neutron capture cross sections for neutrons at thermal energies and the first resonance at 2.154 keV have been measured, yielding a new absolute measurement of $0.238\pm 0.019$ b for the thermal neutron capture cross section. Additionally, the $\gamma$ cascades for captures at both energies have been measured, and cascade models have been developed which may be used by $0\nu \beta \beta$ experiments using ${}^{136}\mathrm{Xe}$.

New experimental data on the $pd\to {}^3\mathrm{He}{\pi }^{+}{\pi }^{-}$ reaction obtained with the COSY-MOMO detector below the three-pion threshold are presented. The reaction was also studied in inverse kinematics with a deuteron beam and the higher counting rates achieved were especially important at low excess energies. The comparison of these data with inclusive $pd\to {}^3\mathrm{He}{X}^0$ rates allowed estimates also to be made of ${\pi }^0{\pi }^0$ production. The results confirm our earlier findings that, close to threshold, there is no enhancement at low excitation energies in the ${\pi }^{+}{\pi }^{-}$ system, where the data seem largely suppressed compared with phase space. Possible explanations for this behavior, such as strong $p$ waves in the ${\pi }^{+}{\pi }^{-}$ system or the influence of two-step processes, are explored.

The isospin- and momentum-dependent interaction using the isospin-dependent quantum molecular dynamics model is improved. The momentum dependence of the interaction is fitted to the optical potentials extracted with proton-nucleus scattering data, while the isospin dependence is adjusted based on the current constraints on the symmetry energy and its density slope at normal density. The resulting parameters of the interaction are used to calculate the effective masses characterized by the nonlocality of the nuclear potential in the spatial coordinates (the so-called effective $k$ masses). It is found that this parametrization can reproduce the effective $k$ masses calculated by the Dirac-Brueckner-Hartree-Fock model. The current constraints on the total symmetry energy can accommodate a wide-range adjustment of the local symmetry energy and effective $k$-mass splitting. Four groups of parameters, which provide different density dependences of symmetry energy and effective $k$-mass splitting, are applied to investigate the isospin diffusion and neutron to proton double ratios in collisions involving ${}^{124}\mathrm{Sn}$ and ${}^{112}\mathrm{Sn}$ nuclei at 50 and 120 MeV/nucleon. Calculations confirm the sensitivity of symmetry energy to the isospin diffusion, but indicate the synchronous effects of symmetry energy and effective $k$-mass splitting on the double ratios.

We demonstrate that the limiting energy available for ejected electrons in the double-$\beta$ decay is diminished by about 400 eV due to inelastic processes in the atomic electronic shell.

Background: Synthesis of superheavy elements is performed by heavy-ion fusion-evaporation reactions. However, fusion is known to be hindered with respect to what can be observed with lighter ions. Thus some delicate ambiguities remain on the fusion mechanism that eventually lead to severe discrepancies in the calculated formation probabilities coming from different fusion models.

Purpose: In the present work, we propose a general framework based upon uncertainty analysis in the hope of constraining fusion models.

Method: To quantify uncertainty associated with the formation probability, we propose to propagate uncertainties in data and parameters using the Monte Carlo method in combination with a cascade code called kewpie2, with the aim of determining the associated uncertainty, namely the $95\%$ confidence interval. We also investigate the impact of different models or options, which cannot be modeled by continuous probability distributions, on the final results. An illustrative example is presented in detail and then a systematic study is carried out for a selected set of cold-fusion reactions.

Results: It is rigorously shown that, at the $95\%$ confidence level, the total uncertainty of the empirical formation probability appears comparable to the discrepancy between calculated values.

Conclusions: The results obtained from the present study provide direct evidence for predictive limitations of the existing fusion-evaporation models. It is thus necessary to find other ways to assess such models for the purpose of establishing a more reliable reaction theory, which is expected to guide future experiments on the production of superheavy elements.

The current most stringent constraints on exotic scalar or tensor couplings in neutron and nuclear $\beta$ decay, involving left-handed neutrinos, are obtained from the Fierz interference term. The sensitivity to this term in a correlation coefficient is usually driven by an energy-averaged kinematic factor that increases monotonically toward smaller values of the $\beta$ endpoint energies. We first point out here that this property does not hold for certain differential observables that are directly sensitive to the Fierz term, such as the $\beta$ or the recoil energy spectrum. This observation is relevant for the selection of sensitive transitions in searches for exotic couplings through spectrum shape measurements. We then point out previous errors in the exploitation of measurements of the $\beta \text{−}\nu$ angular correlation coefficient and discuss their impact on the extraction of constraints on exotic couplings.