Background: Lutetium thermometry has been used to analyze Oklo natural nuclear reactor zones but leads to widely varying and puzzling predictions for the temperatures $T_O$ which in turn impacts bounds on time variation of the fine structure constant $\alpha$.

Purpose: We revisit results for reactor zone RZ10 in light of new measurements of the isomer branching ratio $B^g$ in ${}^{175}$Lu neutron capture at 5 and 25 keV.

Method: We recalculate predictions for $T_O$ as a function of $B^g$ using realistic models of the Oklo neutron flux.

Results: We find $T_O=100\pm 30$ ${}^{\circ }$C using a new value of $B^g$, in contrast to $350<T_O<500$ ${}^{\circ }$C using the evaluated value at thermal energy.

Conclusions: Lutetium thermometry can be applicable to analyses of Oklo reactor data, but a better measurement of $B^g$ with thermal neutrons is needed to confirm the reliability of temperature predictions.

The similarity renormalization group is used to transform Dirac Hamiltonian into a diagonal form, which the upper (lower) diagonal element becomes an operator describing Dirac (anti-)particle. The eigenvalues of the operator are verfied to be in good agreement with that of the original Hamiltonian. Furthermore, the pseudospin symmetry is investigated. It is shown that the pseudospin splittings appearing in the nonrelativistic limit are reduced by the contributions from these terms relating the spin-orbit interactions, added by those relating the dynamical terms, and the quality of pseudospin symmetry origins mainly from the competition of the dynamical effects and the spin-orbit interactions. The spin symmetry of antiparticle spectrum is well reproduced in the present calculations.

We use contracted spin-flavor symmetry which emerges in the large $N_c$ limit of QCD to obtain relations between proton-proton and proton-neutron total cross sections for both polarized and unpolarized scattering. The formalism used is valid in the semiclassical regime in which the relative momentum of the incident nucleons is much larger than the inverse size of the nucleon, provided that certain technical assumptions are met. The relations should be phenomenologically useful provided that $N_c=3$ is sufficiently large so that the large $N_c$ results have at least semiquantitative predictive power. The relations are model independent in the sense that they depend on properties of large $N_c$ QCD only and not on any particular model-dependent details of the nucleon-nucleon interaction. We compare these model-independent results to the experimental data. We find the relation for spin-unpolarized scattering works well empirically. For the case of polarized scattering, the data are consistent with the relations, but the cross sections are too small to make sharp predictions.

Proton elastic scattering angular distributions for the reaction ${}^{17}\mathrm{F}+p$, were measured in inverse kinematics over a wide angular range (${\theta }_{\mathrm{c}.\mathrm{m}.}={50}^{\circ }$–160${}^{\circ }$) at two near-barrier energies of 3.5 and 4.3 MeV/u. The optical potential was probed in a phenomenological and microscopic approach. Moreover, total reaction cross-sections were also determined via optical potential analysis and were used as a signature for probing a possible halo structure of this proton-rich nucleus.

We present a systematics of fission barriers and fission lifetimes for the whole landscape of superheavy elements (SHE), i.e., nuclei with $Z\ge 100$. The fission lifetimes are also compared with the $\alpha$-decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parametrizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bimodal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expected to be produced in the astrophysical $r$ process.

A simple, exactly solvable statistical model is presented for the description of baryonic matter in the thermodynamic conditions associated to the evolution of core-collapsing supernova. It is shown that the model presents a first-order phase transition in the grand-canonical ensemble which is not observed in the canonical ensemble. Similarly to other model systems studied in condensed matter physics, this ensemble inequivalence is accompanied by negative susceptibility and discontinuities in the intensive observables conjugated to the order parameter. This peculiar behavior originates from the fact that baryonic matter is subject to attractive short-range strong forces as well as repulsive long-range electromagnetic interactions, partially screened by a background of electrons. As such, it is expected in any theoretical treatment of nuclear matter in the stellar environment. Consequences for the phenomenology of supernova dynamics are drawn.

Decay of the long-lived ($T_{1/2}=160.44$ d) $K^{\pi }=23/2^{-}$ isomer in ${}^{177}$Lu was investigated using a chemically purified source and the Gammasphere array. New, high-multipolarity M3 and E4 deexcitation branches to the known $I^{\pi }=17/2^{-}$ and 15/2${}^{-}$ members of the $\pi$9/2${}^{-}$[514] band were discovered. The reduced hindrance factors per degree of $K$ forbiddenness deduced for these two transitions are found to be relatively large when compared to similar decays from the $K^{\pi }=37/2^{-}$ ($T_{1/2}=51.4$ min) and $K^{\pi }={16}^{+}$ ($T_{1/2}=31$ yr) isomers in ${}^{177}$Hf and ${}^{178}$Hf, respectively. This is attributed to significant configuration changes that occur in the decay of this ${}^{177}$Lu isomer.

A recent ${}^{20}$O(d,p) ${}^{21}$O experiment, in reverse kinematics, discovered two new states in ${}^{21}$O at 4.77(10) and 6.17(11) MeV, with $J^{\pi }$ assignments of 3/2${}^{+}$ and of 3/2${}^{+}$ or 7/2${}^{-}$, respectively. Both widths and spectroscopic factors were reported, along with the branching ratio for the upper state to decay to the 2${}^{+}$ state of ${}^{20}$O. We have computed single-particle widths for all the relevant decays and have used them to extract additional information for these two states, including the spectroscopic factors for 2${}^{+}$ decay of the upper state with the two possible $J^{\pi }$ values. Our analysis prefers 7/2${}^{-}$ for $J^{\pi }$.

The nuclei ${}^{65,67}$Cu were studied in reactions between a 430-MeV ${}^{64}$Ni beam and a thick ${}^{238}$U target with the Gammasphere array. Decay schemes for both nuclei have been extended, with spin and parity assignments of observed states constrained by measured $\gamma$-ray angular distributions and correlations. Positive-parity level structures, based on $p_{3/2}$ protons coupled to negative-parity states in the Ni cores, have been identified above the known $9/2^{+}$ states. In ${}^{67}$Cu, a negative-parity dipole band built upon a $\pi f_{7/2}^{-1}$ state has been observed, as were two shorter negative-parity sequences. A qualitative description of the level structures has been obtained through comparison with systematics of the odd-$A$${}^{57–71}$Cu isotopes and with states in the neighboring even-even Ni and Zn cores. Shell-model calculations using JUN45 and jj44b effective interactions were performed for ${}^{65,67}$Cu, with jj44b providing overall better agreement with the data. Both are limited, however, by the restriction that the $f_{7/2}$ and $g_{9/2}$ orbitals are not available simultaneously in the basis. Proton $f_{7/2}$ and neutron $g_{9/2}$ orbitals are required for the full negative-parity spectrum of states, while $g_{9/2}$ protons and neutrons are both important for positive-parity levels. The latter states are found to be better described in terms of weak coupling of a proton to the Ni core.

Earlier studies of ${}^{239}$Pu($n,f$) have been extended to incident neutron energies up to 20 MeV within the framework of the event-by-event fission model $\mathtt{FREYA}$, into which we have incorporated multichance fission and pre-equilibrium neutron emission. The main parameters controlling prompt fission neutron evaporation have been identified and the prompt fission neutron spectrum has been analyzed by fitting those parameters to the average neutron multiplicity $\overline{\nu }$ from ENDF-B/VII.0, including the energy-energy correlations in the covariance of $\overline{\nu }\left(E\right)$ obtained by fitting to the experimental $\overline{\nu }$ data used in the ENDF-B/VII.0 evaluation. We present our results, discuss relevant tests of this new evaluation, and describe possible further improvements.

On the basis of systematic measurements of fragmentation reactions, which provide a detailed overview on the velocity distributions of residual nuclei, an improved description of the kinematical properties of the fragmentation residues is established. This work is dedicated to the fluctuations of their momentum distributions. In contrast to previous investigations, limited to close-to-projectile fragments, we extended our study to the entire production range, down to the lightest observed fragments. In this context, besides the contribution of abrasion and evaporation processes, we considered the effect of the thermal breakup on the width of the momentum distributions. By using approximated theoretical descriptions of the different reaction stages, a new analytical formula for the variance of the momentum distribution is derived, which is well adapted to technical applications.

The recent unexpected discovery of asymmetric fission of ${}^{180}$Hg following the electron-capture decay of ${}^{180}$Tl has led to intense interest in experimentally mapping the fission-yield properties over more extended regions of the nuclear chart and compound-system energies. We present here a first calculation of fission-fragment yields for neutron-deficient Hg isotopes, using the recently developed Brownian Metropolis shape-motion treatment. The results for ${}^{180}$Hg are in approximate agreement with the experimental data. For ${}^{174}$Hg the symmetric yield increases strongly with decreasing energy, an unusual feature, which would be interesting to verify experimentally.

It is well known that within self-consistent random-phase approximation (RPA) on top of Hartree-Fock (HF), the translational symmetry should be restored. Because of approximations at the level of the practical implementation, this restoration may be only partial. As a result, one has spurious contributions in the physical quantities that are extracted from RPA. Although there are several recipes in the literature to overcome this drawback to produce transition densities or strength functions that are free from spurious contamination, there is no formalism associated with the full RPA response function. We present such formalism in this paper. Our goal is to avoid spurious contamination when the response function is used in many-body frameworks like the particle-vibration coupling theory.

The Gamow-Teller transition strengths, $B$(GT), in $pf$-shell nuclei are of interest in nuclear physics as well as in nuclear astrophysics. A high-resolution (${}^3\mathrm{He},t$) charge-exchange (CE) reaction was performed on the $T_z=+1$ nucleus ${}^{54}$Fe at 0${}^{\circ }$ and at an intermediate incident energy of 140 MeV/nucleon for the study of precise GT transition strengths to the final $T_z=0$ nucleus ${}^{54}$Co. By applying dispersion matching techniques for a high-quality ${}^3$He beam at RCNP, an energy resolution of 21 keV and an angular resolution of 5 mr were realized. The bumplike structure of the GT resonance observed in low-resolution CE reactions at around the excitation energy ($E_x$) of 10 MeV was resolved in individual $L$ $=$ 0, GT states. Excitation strengths were obtained for these GT states. If the $R^2$ value that is defined by the ratio between GT and Fermi unit cross sections is known, the $B$(GT) values can be determined from the excitation strengths. For the derivation of the $R^2$ value, the “merged analysis” combining the GT strength distribution from the ${}^{54}$Fe(${}^3\mathrm{He},t$)${}^{54}$Co study and the half-life from a ${}^{54}$Ni $\beta$ decay was used, where $T=1$ isospin symmetry for $A=54$ isobars was assumed. The GT strengths were compared with a shell-model calculation using the GXPF1 interaction. The final GT states can have the isospin values $T$ $=$ 0, 1, and 2. The isospin $T$ of each GT state observed in the $8.3\le E_x\le 12.0$ MeV region of the ${}^{54}$Fe(${}^3\mathrm{He},t$)${}^{54}$Co spectrum was identified by comparing the excitation strength with that of corresponding $M1$ state observed in a ${}^{54}$Fe($p,p^{\prime }$)${}^{54}$Fe experiment. The $B$(GT) values of the states identified to have $T=2$, in particular, are of importance for the calculation of the electron capture rates at the core-collapse stage of presupernovae. The $B$(GT) strengths were further compared with $B\left(M1\right)$ strengths measured in the ${}^{54}$Fe($e,e^{\prime }$)${}^{54}$Fe reaction. In the $M1$ excitation using an electromagnetic probe, isoscalar (IS) and isovector (IV) orbital type operators are active in addition to the IV spin type operator that mediates the GT transitions. The contributions of the IS and IV orbital terms were studied by calculating the ratio of the strengths of analogous $M1$ and GT transitions.

A novel source of nonlocality was introduced into the optical potential in a previous work. We expressed the nonlocality in the form of a surface term, which is proportional to the gradient of the nuclear matter density of the target nucleus. In this work, we have tested the suitability of the surface term form by considering neutron elastic scattering from ${}^{40}$Ca, where, unlike light nuclei considered previously, the gradient of the nuclear density is important only close to the nuclear surface. The model resulted in excellent fits to the $N$-${}^{40}$Ca elastic angular distributions and led to very good theoretical predictions for the analyzing power $A_y\left(\theta \right)$. Further, the fit parameters varied more slowly and smoothly with the incident energy compared to the case of neutron elastic scattering from the light ${}^{12}$C nucleus.

The fusion excitation function of ${}^{40}\mathrm{Ca}+{}^{40}\mathrm{Ca}$ has been measured from well above the Coulomb barrier, down to low energies where the cross section is as small as $\simeq$20 $\mu$b, and the astrophysical $S$ factor possibly reaches a maximum vs energy. The results of coupled-channels calculations using the $\mathrm{M}3\mathrm{Y}+\mathrm{repulsion}$ potential are presented. A detailed comparison is made with recently published data on the fusion of ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$ and of ${}^{48}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, including the excitation functions, their low-energy slopes and the barrier distributions. The presence of the fusion hindrance phenomenon in all cases is pointed out, as well as the influence of the strong octupole excitation in ${}^{40}$Ca and of nucleon transfer channels with positive $Q$ values in ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$.

Collinear factorized perturbative QCD model predictions are compared for $p+\mathrm{Pb}$ at 4.4$A$ TeV to test nuclear shadowing of parton distribution at the CERN Large Hadron Collider (LHC). The nuclear modification factor (NMF), $R_{p\mathrm{Pb}}(y=0,p_T<20\mathrm{GeV}/\mathit{c})=d{n}_{p\mathrm{Pb}}/\left[N_{\mathrm{coll}}\left(b\right)d{n}_{pp}\right]$, is computed with an electron-nucleus ($e+A$) global fit with different nuclear shadow distributions and compared to the fixed $Q^2$ shadow ansatz used in Monte Carlo Heavy Ion Jet Interacting Generator (HIJING)–type models. Because of the rapid Dokshitzer Gribov Lipatov Altarelli Parisi (DGLAP) reduction of shadowing with increasing $Q^2$ used in the $e+A$ global fit, our results confirm that no significant initial state suppression is expected [$R_{p\mathrm{Pb}}\left(p_T\right)=1\pm 0.1$] in the $p_T$ range 5 to 20 GeV/$c$. In contrast, the fixed $Q^2$ shadowing models assumed in HIJING-type models predict in the range above $p_T$ a sizable suppression, $R_{p\mathrm{Pb}}\left(p_T\right)=0.6$–0.7, at midpseudorapidity that is similar to the color glass condensate (CGC) model predictions. For central ($N_{\mathrm{coll}}=12$) $p+\mathrm{Pb}$ collisions and at forward pseudorapidity ($\eta =6$), the HIJING-type models predict smaller values of nuclear modification factors [$R_{p\mathrm{Pb}}\left(p_T\right)$] than in minimum-bias events at midpseudorapidity ($\eta =0$). Observation of $R_{p\mathrm{Pb}}(p_T=5-20\mathrm{GeV}/\mathit{c})\lesssim 0.6$ for minimum bias $p+A$ collisions would pose a serious difficulty for separating initial-state from final-state interactions in Pb + Pb collisions at LHC energies.

Energy-dependent and single-energy fits to the existing pion photoproduction database have been updated to cover the region from threshold to 2.7 GeV in laboratory photon energy. Revised resonance photo-decay couplings have been extracted and compared to previous determinations. The influence of recent measurements is displayed. Remaining problems and future approaches are discussed.

The nuclear symmetry energy $E_{\mathrm{sym}}\left(\rho \right)$ and its density slope $L\left(\rho \right)$ can be decomposed analytically in terms of the single-nucleon potential in isospin asymmetric nuclear matter. Using three popular nuclear effective interaction models which have been extensively used in nuclear structure and reaction studies, namely, the isospin and momentum-dependent MDI interaction model, the Skyrme-Hartree-Fock approach, and the Gogny-Hartree-Fock approach, we analyze the contribution of different terms in the single-nucleon potential to $E_{\mathrm{sym}}\left(\rho \right)$ and $L\left(\rho \right)$. Our results show that the observed different density behaviors of $E_{\mathrm{sym}}\left(\rho \right)$ for different interactions are essentially due to the variation of the symmetry potential $U_{\mathrm{sym},1}(\rho ,k)$. Furthermore, we find that the contribution of the second-order symmetry potential $U_{\mathrm{sym},2}(\rho ,k)$ to $L\left(\rho \right)$ generally cannot be neglected. Moreover, our results demonstrate that the magnitude of $U_{\mathrm{sym},2}(\rho ,k)$ is generally comparable with that of $U_{\mathrm{sym},1}(\rho ,k)$, indicating that the second-order symmetry potential $U_{\mathrm{sym},2}(\rho ,k)$ may have significant corrections to the widely used Lane approximation for the single-nucleon potential in extremely neutron rich or proton rich nuclear matter.

We present event-by-event viscous hydrodynamic calculations of the anisotropic flow coefficients $v_2$ to $v_5$ for heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC). We study the dependence of different flow harmonics on shear viscosity and the morphology of the initial state. $v_3$ and higher flow harmonics exhibit a particularly strong dependence on both the initial granularity and shear viscosity. We argue that a combined analysis of all available flow harmonics has the potential to determine $\eta /s$ of the quark gluon plasma more precisely than previously. Presented results strongly hint at a value ${(\eta /s)}_{QGP}<2/4\pi$ at RHIC. Furthermore, we demonstrate the effect of shear viscosity on pseudorapidity spectra and the mean transverse momentum as a function of rapidity.