The observed primordial ${}^7$Li abundance in metal-poor halo stars is found to be lower than its Big-Bang nucleosynthesis (BBN) calculated value by a factor of approximately three. Some recent works suggested the possibility that this discrepancy originates from missing resonant reactions which would destroy ${}^7$Be, parent of ${}^7$Li. The most promising candidate resonances which were found include a possibly missed 1${}^{-}$ or 2${}^{-}$ narrow state around 15 MeV in the compound nucleus ${}^{10}$C formed by ${}^7$Be+${}^3$He and a state close to 7.8 MeV in the compound nucleus ${}^{11}$C formed by ${}^7$Be+${}^4$He. In this work, we studied the high excitation energy region of ${}^{10}$C and the low excitation energy region in ${}^{11}$C via the reactions ${}^{10}$B(${}^3$He,$t$)${}^{10}$C and ${}^{11}$B(${}^3$He,$t$)${}^{11}$C, respectively, at the incident energy of 35 MeV. Our results for ${}^{10}$C do not support ${}^7$Be+${}^3$He as a possible solution for the ${}^7$Li problem. Concerning ${}^{11}$C results, the data show no new resonances in the excitation energy region of interest and this excludes the ${}^7$Be+${}^4$He reaction channel as an explanation for the ${}^7$Li deficit.

Using the $\delta$-shell representation we present a successful fit to neutron-proton and proton-proton scattering data below the pion production threshold. A detailed overview of the theory necessary to calculate observables with this potential is presented. A new data selection process is used to obtain the largest mutually consistent data base. The analysis includes data within the years 1950 to 2013. Using 46 parameters we obtain ${\chi }^2/N_{\mathrm{data}}=1.04$ with $N_{\mathrm{data}}=6713$ including normalization data. Phase shifts with error bars are provided.

Using the relativistic point-coupling model with the density functional PC-PK1, the magnetic moments of the nuclei ${}^{207}$Pb, ${}^{209}$Pb, ${}^{207}$Tl, and ${}^{209}$Bi with a $jj$ closed-shell core ${}^{208}$Pb are studied on the basis of relativistic mean field theory. The corresponding time-odd fields, the one-pion exchange currents, and the first- and second-order corrections are taken into account. The present relativistic calculations are in reasonable agreement with the data. The relative deviation between theory and experiment for these four nuclei is $6.1\%$ for the relativistic calculations and somewhat smaller than the value of $13.2\%$ found in earlier nonrelativistic investigations. It turns out that the pion meson is important for the description of magnetic moments, first by means of one-pion exchange currents and second by the residual interaction provided by the pion exchange.

The dipole response of ${}_{34}^{76}$Se in the energy range from 4 to 9 MeV has been analyzed using a $(\vec{\gamma },{\gamma }^{\prime })$ polarized photon scattering technique, performed at the High Intensity $\gamma$-Ray Source facility at Triangle Universities Nuclear Laboratory, to complement previous work performed using unpolarized photons. The results of this work offer both an enhanced sensitivity scan of the dipole response and an unambiguous determination of the parities of the observed $J=1$ states. The dipole response is found to be dominated by $E1$ excitations, and can reasonably be attributed to a pygmy dipole resonance. Evidence is presented to suggest that a significant amount of directly unobserved excitation strength is present in the region, due to unobserved branching transitions in the decays of resonantly excited states. The dipole response of the region is underestimated when considering only ground state decay branches. We investigate the electric dipole response theoretically, performing calculations in a three-dimensional (3D) Cartesian-basis time-dependent Skyrme-Hartree-Fock framework.

The ${}^{12}$C(${}^4$He,${}^8$Be)${}^8$Be and ${}^{12}$C(${}^4$He,${}^{12}$C${}^{*}$ $\to$ ${}^8$Be+$\alpha$)$\alpha$ reactions have been measured with beam energies ranging from 12.2 to 20.0 MeV. The $\alpha$ particles emitted directly and following the decay of ${}^8$Be and ${}^{12}$C${}^{*}$ were detected in an array of four double sided silicon strip detectors. An analysis of the angular distributions obtained for the ${}^{12}$C(${}^4$He,${}^8$Be)${}^8$Be channel provides no evidence to support the previously proposed rotational structure consisting of a rigid, linear, arrangement of four $\alpha$ particles in ${}^{16}$O.

It is generally accepted that the main cause of ultracold neutron (UCN) losses in storage traps is upscattering to the thermal energy range by hydrogen adsorbed on the surface of the trap walls. However, the data on which this conclusion is based are poor and contradictory. Here we report a measurement, performed at the Los Alamos National Laboratory UCN source, of the average energy of the flux of upscattered neutrons after the interaction of UCN with hydrogen bound in the semicrystalline polymer PMP (trade name TPX), [C${}_6$H${}_{12}$]${}_n$. Our analysis, performed with the mcnp code which applies the neutron-scattering law to UCN upscattered by bound hydrogen in semicrystalline polyethylene, [C${}_2$H${}_4$]${}_n$, leads us to a flux average energy value of $26\pm 3$ meV, in contradiction to previously reported experimental values of 10 to 13 meV and in agreement with the theoretical models of neutron heating implemented in mcnp.

The reaction $K^{-}p\to \Lambda \eta$ at low energies is studied with a chiral quark model approach. Good descriptions of the existing experimental data are obtained. It is found that $\Lambda \left(1670\right)$ dominates the reaction around threshold. Furthermore, $u$- and $t$-channel backgrounds play crucial roles in this reaction as well. The contributions from the $D$-wave state $\Lambda \left(1690\right)$ are negligibly small for its tiny coupling to $\eta \Lambda$. To understand the strong coupling properties of the low-lying negative parity $\Lambda$ resonances extracted from the $\overline{K}N$ scattering, we further study their strong decays. It is found that these resonances are most likely mixed states between different configurations. Considering these low-lying negative parity $\Lambda$ resonances as mixed three-quark states, we can reasonably understand both their strong decay properties from Particle Data Group and their strong coupling properties extracted from the $\overline{K}N$ scattering. As a byproduct, we also predict the strong decay properties of the missing $D$-wave state $|\Lambda {\frac{3}{2}}^{-}{\rangle }_3$ with a mass of $\sim 1.8$ GeV. We suggest our experimental colleagues search it in the $\Sigma \left(1385\right)\pi$ and $\Sigma \pi$ channels.

Orthopositronium (o-Ps) formation and decay can replace the annihilation process, when a positron interacts in liquid scintillator media. The delay induced by the positronium decay represents either a potential signature for antineutrino detection, via inverse $\beta$ decay, or to identify and suppress positron background, as recently demonstrated by the Borexino experiment. The formation probability and decay time of o-Ps depend strongly on the surrounding material. In this paper, we characterize the o-Ps properties in liquid scintillators as function of concentrations of gadolinium, lithium, neodymium, and tellurium dopers used by present and future neutrino experiments. In particular, gadolinium and lithium are high neutron cross section isotopes, widely used in reactor antineutrino experiments, while neodymium and tellurium are double $\beta$ decay emitters, employed to investigates the Majorana neutrino nature. Future neutrino experiments may profit from the performed measurements to tune the preparation of the scintillator in order to maximize the o-Ps signature, and therefore the discrimination power.

We study the impact of neutrino-pair production from the de-excitation of highly excited heavy nuclei on core-collapse supernova simulations, following the evolution up to several 100 ms after core bounce. Our study is based on the agile-boltztransupernova code, which features general relativistic radiation hydrodynamics and accurate three-flavor Boltzmann neutrino transport in spherical symmetry. In our simulations the nuclear de-excitation process is described in two different ways. At first we follow the approach proposed by Fuller and Meyer [Astrophys. J. 376, 701 (1991)], which is based on strength functions derived in the framework of the nuclear Fermi-gas model of noninteracting nucleons. Second, we parametrize the allowed and forbidden strength distributions in accordance with measurements for selected nuclear ground states. We determine the de-excitation strength by applying the Brink hypothesis and detailed balance. For both approaches, we find that nuclear de-excitation has no effect on the supernova dynamics. However, we find that nuclear de-excitation is the leading source for the production of electron antineutrinos as well as heavy-lepton-flavor (anti)neutrinos during the collapse phase. At sufficiently high densities, the associated neutrino spectra are influenced by interactions with the surrounding matter, making proper simulations of neutrino transport important for the determination of the neutrino-energy loss rate. We find that, even including nuclear de-excitations, the energy loss during the collapse phase is overwhelmingly dominated by electron neutrinos produced by electron capture.

We use the relativistic mean field theory to study the finite temperature nuclear matter properties. The effects of isoscalar $\sigma \text{−}\omega$ coupling on the equation of state and finite temperature properties of symmetric and asymmetric nuclear matter are investigated carefully. For comparison, we also discuss the properties of two nonlinear $\sigma$ self-coupling models, namely NL-SH and NL3. It is found that the $\sigma \text{−}\omega$ coupling term can soften the equation of state, but has very limited influence to the critical temperature of the nuclear matter liquid-gas phase transition.

We present a new Hartree-Fock-Bogoliubov nuclear mass model based on standard forms of Skyrme and pairing functionals, which corresponds to the most accurate mass model we ever achieved within the framework of the nuclear energy density functional theory. Our new mass model is characterized by a model standard deviation ${\sigma }_{\mathrm{mod}}=0.500$ MeV with respect to essentially all the 2353 available mass data for nuclei with neutron and proton numbers larger than 8. At the same time, the underlying Skyrme functional yields a realistic description of infinite homogeneous nuclear matter properties, as determined by realistic calculations and by experiments; these include in particular the incompressibility coefficient, the pressure in charge-symmetric nuclear matter, the neutron-proton effective mass splitting, the stability against spin and spin-isospin fluctuations, as well as the neutron-matter equation of state.

In the representation space approach a useful analytical expression for the integral transform of the Coulomb Green's function by the Hankel function is constructed via Sturmian representation of the bound-state Coulomb Green's function. This integral transform is exploited to construct off-shell Jost solutions for motion in Coulomb and Coulomb plus separable interactions in the maximal reduced form. The expressions for the corresponding off-shell $T$ matrices are also constructed by using a modified relation between the off-shell physical solution and the $T$ matrix that does not involve the potential explicitly. Finally, off-shell $T$ matrices are computed to examine the role of the Coulomb interaction in proton-proton scattering in the ${}^1{S}_0$ channel.

Excited states of the isotope ${}^{234}$U were studied employing the one-neutron transfer reaction ${}^{235}\mathrm{U}{(d,t)}^{234}$U at a beam energy of 11 MeV. The reaction channel was selected by an identification of the outgoing tritons in a $\Delta E$-$E$ measurement. In coincidence with the tritons, $\gamma$ rays were also detected with the highly efficient MINIBALL spectrometer. Based on the analysis of $\gamma \gamma$ coincidence data, the level scheme of ${}^{234}$U was extended. The 4${}^{+}$ state at an energy of 1886.7 keV provides evidence for a possible two-phonon $\gamma \gamma$ excitation, which is based on three $\gamma$ transitions from this state to the $\gamma$ vibrational band. However, this state is populated with a high cross section via the one-neutron transfer reaction, which is not expected for a highly collective excitation. The situation is compared to other known cases from the rare-earth region and to the neighboring isotone ${}^{232}$Th, which so far is the only known case for a two-phonon excitation in the actinide region.

The inclusive cross sections of the $\alpha$ particles produced in the reaction ${}^6$Li + ${}^{159}$Tb have been measured at energies around the Coulomb barrier. The measured cross sections are found to be orders of magnitude larger than the calculated cross sections of ${}^6$Li breaking into $\alpha$ and $d$ fragments, thus indicating contributions from other processes. The experimental cross sections of $1n$-stripping and $1n$-pickup processes have been determined from an entirely different measurement, reported earlier. Apart from incomplete fusion and $d$-transfer processes, the $1n$-stripping process is found to be a significant contributor to the inclusive $\alpha$-particle cross sections in this reaction.

Three-dimensional pion and kaon emission source functions are extracted from hydrokinetic model (HKM) simulations of central Au+Au collisions at the top Relativistic Heavy Ion Collider (RHIC) energy $\sqrt{s_{NN}}=200$ GeV. The model describes well the experimental data, previously obtained by the PHENIX and STAR collaborations using the imaging technique. In particular, the HKM reproduces the non-Gaussian heavy tails of the source function in the pair transverse momentum (out) and beam (long) directions, observed in the pion case and practically absent for kaons. The role of rescatterings and long-lived resonance decays in forming the mentioned long-range tails is investigated. The particle rescattering contribution to the out tail seems to be dominating. The model calculations also show substantial relative emission times between pions (with mean value 13 fm/$c$ in the longitudinally comoving system), including those coming from resonance decays and rescatterings. A prediction is made for the source functions in Large Hadron Collider (LHC) Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV, which are still not extracted from the measured correlation functions.

The hydrodynamic description of a fireball produced in high-energy heavy-ion collisions has been recently supplemented by a very successful study of acoustic perturbation created by the initial-state perturbations. We discuss sound produced at later stages of the collision, as the temperature drops below critical, $T<T_c$, and originated from the Rayleigh-type collapse of the quark-gluon plasma clusters. In a certain analytic approximation we study distorted sound spheres and calculate modifications of the particle spectra and two-particle correlators induced by them. Unlike for initial-state perturbations studied previously, we propose to look for those late-time sounds using rapidity correlations, rather than the azimuthal angles of the particles. We then summarize known data on rapidity correlations from RHIC and LHC, suggesting that the widening of those can be the first signature of the late-time sounds.

Available experimental data are analyzed to derive simple parametrizations for the mean charged-hadron multiplicities in charged-current neutrino and antineutrino interactions with hydrogen and deuterium targets. The obtained results can be used in the (anti)neutrino-induced hadronic shower modeling.

We calculate thermal conductivity and shear viscosity of nucleons in the dense nuclear matter of neutron star cores in the nonrelativistic Brueckner-Hartree-Fock framework. The nucleon-nucleon interaction is described by the Argonne v18 potential with addition of the Urbana IX effective three-body forces. We find that this three-body force leads to a decrease of the kinetic coefficients with respect to the two-body case. The results of calculations are compared with electron and muon transport coefficients as well as with the results of other authors.

The rate of oxygen formation determines the C/O ratio during stellar helium burning. It is the single most important nuclear input in stellar evolution theory, including the evolution of type II and type Ia supernova. However, the low-energy cross section of the fusion of ${}^4$He $+{}^{12}$C, denoted as the ${}^{12}$C${(\alpha ,\gamma )}^{16}$O reaction, still remains uncertain. I analyze and critically review the most recent measurements of complete angular distributions of the outgoing $\gamma$ rays at very low energies ($E_{\mathrm{c}.\mathrm{m}.}\ge 1.0$ MeV). My analysis of the angular distributions measured with the EUROGAM/GANDI arrays leads to considerably larger error bars than have been published, which excludes them from the current sample of “world data.” I show that the current sample of “world data” of the measured $E2$ cross-section factors below 1.7 MeV cluster into two distinct groups that lead to two distinct extrapolations: $S_{E2}\left(300\right)\approx 60$ or $S_{E2}\left(300\right)\approx 154$ keVb. There is a discrepancy between the measured $E$1-$E$2 phase difference (${\varphi }_{12}$) and unitarity as required by the Watson theorem, which suggests systematic problem(s) in some of the measured $\gamma$-ray angular distributions. The ambiguity of the extrapolated $S_{E2}\left(300\right)$ together with the previously observed ambiguity of $S_{E1}\left(300\right)$ (approximately 80 or 10 keVb) must be resolved by future measurements of complete and detailed angular distributions of the ${}^{12}$C$(\alpha ,\gamma )$ reaction at very low energies ($E_{\mathrm{c}.\mathrm{m}.}\le 1.0$ MeV).