The absolute neutron-capture cross section of ${}^{242}\mathrm{Pu}$ was measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. The first direct measurement of the ${}^{242}\mathrm{Pu}(n,\gamma )$ cross section was made over the incident neutron energy range from thermal to $\approx 6$ keV, and the absolute scale of the $\left(n,\gamma \right)$ cross section was set according to the known ${}^{239}\mathrm{Pu}(n,f)$ resonance at $E_{n,R}=7.83$ eV. This was accomplished by adding a small quantity of ${}^{239}\mathrm{Pu}$ to the ${}^{242}\mathrm{Pu}$ sample. The relative scale of the cross section, with a range of four orders of magnitude, was determined for incident neutron energies from thermal to $\approx 40$ keV. Our data, in general, are in agreement with previous measurements and those reported in ENDF/B-VII.1; the ${}^{242}\mathrm{Pu}(n,\gamma )$ cross section at the $E_{n,R}=2.68$ eV resonance is within $2.4\%$ of the evaluated value. However, discrepancies exist at higher energies; our data are $\approx 30\%$ lower than the evaluated data at $E_n\approx 1$ keV and are approximately $2\sigma$ away from the previous measurement at $E_n\approx 20$ keV.

Mass-spectrometric analyses of Xe released from acid-treated U ore reveal that apparent Xe fission yields significantly deviate from the normal values. The anomalous Xe structure is attributed to hemically ractionated ission (CFF), previously observed only in materials experienced neutron bursts. The least retentive CFF-Xe isotopes, ${}^{136}\mathrm{Xe}$ and ${}^{134}\mathrm{Xe}$, typically escape in 2:1 proportion. Xe retained in the sample is complimentarily depleted in these isotopes. This nucleochemical process allows understanding of unexplained Xe isotopic structures in several geophysical environments, which include well gasses, ancient anorthosite, some mantle rocks, as well as terrestrial atmosphere. CFF is likely responsible for the isotopic difference in Xe in the Earth's and Martian atmospheres and it is capable of explaining the relationship between two major solar system Xe carriers: the Sun and phase-Q, found in meteorites.

We calculate cross sections for diphoton production in (semi)exclusive $\mathrm{PbPb}$ collisions, relevant for the CERN Large Hadron Collider (LHC). The calculation is based on the equivalent photon approximation in the impact parameter space. The cross sections for the elementary $\gamma \gamma \to \gamma \gamma$ subprocess are calculated including two different mechanisms. We take into account box diagrams with leptons and quarks in the loops. In addition, we consider a vector-meson dominance (VDM-Regge) contribution with virtual intermediate hadronic (vector-like) excitations of the photons. We get measurable cross sections in $\mathrm{PbPb}$ collisions. This opens a possibility to study the $\gamma \gamma \to \gamma \gamma$ (quasi)elastic scattering at the LHC. We present many interesting differential distributions which could be measured by the ALICE, CMS, or ATLAS Collaborations at the LHC. We study whether a separation or identification of different components (boxes, VDM-Regge) is possible. We find that the cross section for elastic $\gamma \gamma$ scattering could be measured in the heavy-ion collisions for subprocess energies smaller than $W_{\gamma \gamma }\approx 15\text{–}20$ GeV.

The correlation between the transverse momentum and the azimuthal asymmetry of the flow is studied. A correlation coefficient is defined between the average transverse momentum of hadrons emitted in an event and the square of the elliptic or triangular flow coefficient. The hydrodynamic model predicts a positive correlation of the transverse momentum with the elliptic flow, and almost no correlation with the triangular flow in Pb-Pb collisions at LHC energies. In $p$-Pb collisions the new correlation observable is very sensitive to the mechanism of energy deposition in the first stage of the collision.

The nuclear level density and the $\gamma$-ray strength function have been extracted for ${}^{89}\mathrm{Y}$ by using the Oslo method on ${}^{89}\mathrm{Y}(p,p^{\prime }\gamma ){}^{89}\mathrm{Y}$ coincidence data. The $\gamma$-ray strength function displays a low-energy enhancement consistent with previous observations in this mass region $\left({}^{93\text{–}98}\mathrm{Mo}\right)$. Shell-model calculations support the conclusion that the observed enhancement is due to strong, low-energy $M1$ transitions at high excitation energies. The data were further used as input for calculations of the ${}^{88}\mathrm{Sr}(p,\gamma ){}^{89}\mathrm{Y}$ and ${}^{88}\mathrm{Y}(n,\gamma ){}^{89}\mathrm{Y}$ cross sections with the talys reaction code. Comparison with cross-section data, where available, as well as with values from the BRUSLIB library, shows a satisfying agreement.

We evidence a staggering effect of the experimental spectroscopic factors corresponding to even-even and odd-mass (odd-mass and odd-odd) $\alpha$ emitters. The comparison to the theoretical estimate within the standard Bardeen-Cooper-Schrieffer (BCS) approach reveals a similar staggering, but with a different behavior. It turns out that the ratio between corresponding experimental and theoretical spectroscopic factors is proportional to the experimental reduced decay width. A similar dependence was found in a previous work between the strength of the quadrupole-quadrupole $\alpha$-core interaction, describing the $\alpha$-decay fine structure and the reduced width. Thus, the even-odd staggering effect in the spectroscopic factor is a new evidence of the $\alpha$-clustering phenomenon in medium and heavy nuclei.

In order to investigate the nuclear symmetry energy at high density, we study the pion production in central collisions of neutron-rich nuclei ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at 300 MeV/nucleon using a new approach that combines antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and $\mathrm{\Delta }$ resonances in the reaction process are handled by JAM. We see the mechanism by which the $\mathrm{\Delta }$ resonance and pions are produced, reflecting the dynamics of neutrons and protons. We also investigate the impacts of cluster correlations as well as of the high-density symmetry energy on the nucleon dynamics and consequently on the pion ratio. We find that the ${\mathrm{\Delta }}^{-}/{\mathrm{\Delta }}^{++}$ production ratio agrees very well with the neutron-proton squared ratio ${(N/Z)}^2$ in the high-density and high-momentum region. We show quantitatively that the $\mathrm{\Delta }$ production ratio, and therefore ${(N/Z)}^2$, are directly reflected in the ${\pi }^{-}/{\pi }^{+}$ ratio, with modification in the final stage of the reaction.

Background: ${}^{92}\mathrm{Mo}$ is the most abundant nucleus of the $p$ nuclei, with an isotopic abundance of more than 14 %. The $\gamma \text{-process}$ nucleosynthesis is believed to produce ${}^{92}\mathrm{Mo}$ but fails to explain its large abundance, especially with respect to the other $p$ nuclei produced in the same stellar environment. Further studies require precise nuclear models for the calculation of reaction cross sections.

Purpose: A measurement of the total and partial cross sections of the ${}^{92}\mathrm{Mo}(p,\gamma ){}^{93}\mathrm{Tc}$ reaction allows for a stringent test of statistical-model predictions. Not only different $\text{proton}+\text{nucleus}$ optical model potentials, but also the $\gamma \text{-ray}$ strength function of ${}^{93}\mathrm{Tc}$ can be investigated. In addition, high-resolution in-beam $\gamma \text{-ray}$ spectroscopy enables the determination of new precise nuclear structure data for ${}^{93}\mathrm{Tc}$.

Method: Total and partial cross-section values were measured by using the in-beam method. Prompt $\gamma$ rays emitted during the irradiation of ${}^{92}\mathrm{Mo}$ with protons at seven different energies between 3.7  and 5.3 MeV were detected by using the high-purity germanium (HPGe) detector array HORUS at the Institute for Nuclear Physics, University of Cologne. The $\gamma \gamma \text{-coincidence}$ method was applied to correlate $\gamma \text{-ray}$ cascades in ${}^{93}\mathrm{Tc}$ with their origin in the ${}^{92}\mathrm{Mo}+p$ compound state.

Results: The measured cross sections are compared to Hauser–Feshbach calculations by using the statistical-model code talys on the basis of different nuclear physics input models. Using default settings based on standard phenomenological models, the experimental values cannot be reproduced. A shell-model calculation was carried out to predict the low-energy $M1$ strength in ${}^{93}\mathrm{Tc}$. Together with Gogny–Hartree–Fock–Bogoliubov (Gogny-HFB) or Skyrme-HFB plus quasi-particle random-phase approximation (QRPA) models for the $\gamma \text{-ray}$ strength function, the agreement between experimental data and theoretical predictions could be significantly improved. In addition, deviations from the adopted level scheme were found.

Conclusions: By using Gogny- or $\text{Skyrme-}\text{HFB}+\text{QRPA} E1$ and shell-model $M1$ strength functions, statistical-model predictions can be significantly improved. Partial cross sections provide a valuable testing ground for $\gamma \text{-ray}$ strength functions for nuclear astrophysics applications. In addition, they can be used to investigate nuclear-structure properties of the compound nucleus.

We assess the accuracy of finite-temperature mean-field theory using as a standard the Hamiltonian and model space of the shell model Monte Carlo calculations. Two examples are considered: the nucleus ${}^{162}\mathrm{Dy}$, representing a heavy deformed nucleus, and ${}^{148}\mathrm{Sm}$, representing a nearby heavy spherical nucleus with strong pairing correlations. The errors inherent in the finite-temperature Hartree-Fock and Hartree-Fock-Bogoliubov approximations are analyzed by comparing the entropies of the grand canonical and canonical ensembles, as well as the level density at the neutron resonance threshold, with shell model Monte Carlo calculations, which are accurate up to well-controlled statistical errors. The main weak points in the mean-field treatments are found to be: (i) the extraction of number-projected densities from the grand canonical ensembles, and (ii) the symmetry breaking by deformation or by the pairing condensate. In the absence of a pairing condensate, we confirm that the usual saddle-point approximation to extract the number-projected densities is not a significant source of error compared to other errors inherent to the mean-field theory. We also present an alternative formulation of the saddle-point approximation that makes direct use of an approximate particle-number projection and avoids computing the usual three-dimensional Jacobian of the saddle-point integration. We find that the pairing condensate is less amenable to approximate particle-number projection methods because of the explicit violation of particle-number conservation in the pairing condensate. Nevertheless, the Hartree-Fock-Bogoliubov theory is accurate to less than one unit of entropy for ${}^{148}\mathrm{Sm}$ at the neutron threshold energy, which is above the pairing phase transition. This result provides support for the commonly used “back-shift” approximation, treating pairing as only affecting the excitation energy scale. When the ground state is strongly deformed, the Hartree-Fock entropy is significantly lower than the shell model Monte Carlo entropy at low temperatures because of the missing contribution of rotational degrees of freedom. However, treating the rotational bands in a simple model, we find that the entropy at moderate excitation energies is reproduced to within two units, corresponding to an error in the level density of less than an order of magnitude. We conclude with a discussion of methods that have been advocated as beyond the mean-field approximation, and their prospects to address the issues we have identified.

Background: Proton and neutron radii are fundamental quantities of atomic nuclei. To study the sizes of short-lived unstable nuclei, there is a need for an alternative to electron scattering.

Purpose: The recent paper by Horiuchi et al. [Phys. Rev. C 89, 011601(R) (2014)] proposed a possible way of extracting the matter and neutron-skin thickness of light- to medium-mass nuclei using total reaction cross section, ${\sigma }_R$. The analysis is extended to medium to heavy nuclei up to lead isotopes with due attention to Coulomb breakup contributions as well as density distributions improved by paring correlation.

Methods: We formulate a quantitative calculation of ${\sigma }_R$ based on the Glauber model including the Coulomb breakup. To substantiate the treatment of the Coulomb breakup, we also evaluate the Coulomb breakup cross section due to the electric dipole field in a canonical-basis-time-dependent-Hartree-Fock-Bogoliubov theory in the three-dimensional coordinate space.

Results: We analyze ${\sigma }_R$'s of 103 nuclei with $Z=20$, 28, 40, 50, 70, and 82 incident on light targets, ${}^{1,2}\mathrm{H}$, ${}^4\mathrm{He}$, and ${}^{12}\mathrm{C}$. Three kinds of Skyrme interactions are tested to generate those wave functions. To discuss possible uncertainty due to the Coulomb breakup, we examine its dependence on the target, the incident energy, and the Skyrme interaction. The proton is a most promising target for extracting the nuclear sizes as the Coulomb excitation can safely be neglected. We find that the so-called reaction radius, $a_R=\sqrt{{\sigma }_R/\pi }$, for the proton target is very well approximated by a linear function of two variables, the matter radius and the skin thickness, in which three constants depend only on the incident energy. We quantify the accuracy of ${\sigma }_R$ measurements needed to extract the nuclear sizes.

Conclusions: The proton is the best target because, once the incident energy is set, its $a_R$ is very accurately determined by only the matter radius and neutron-skin thickness. If ${\sigma }_R$'s at different incident energies are measured, one can determine both the proton and neutron radii for unstable nuclei as well. The total reaction cross sections calculated in this paper are given as Supplemental Material for the sake of future measurements.

Spectral functions of the pseudoscalar $D$ meson in the nuclear medium are analyzed using QCD sum rules and the maximum entropy method. This approach enables us to extract the spectral functions without any phenomenological assumption, and thus to visualize in-medium modification of the spectral functions directly. It is found that the reduction of the chiral condensates of dimension 3 and 5 causes the masses of both $D^{+}$ and $D^{-}$ mesons to grow gradually at finite density. Additionally, we construct charge-conjugate-projected sum rules and find a $D^{+}–D^{-}$ mass splitting of about $-15$ MeV at nuclear saturation density.

In this work, we present a new and general method for measuring the astrophysical $S$ factor of nuclear reactions in laser-induced plasmas and we apply it to ${}^2\mathrm{H}(d,n){}^3\mathrm{He}$. The experiment was performed with the Texas Petawatt Laser, which delivered 150–270 fs pulses of energy ranging from 90 to 180 J to ${\mathrm{D}}_2$ or ${\mathrm{CD}}_4$ molecular clusters (where D denotes ${}^2\mathrm{H})$. After removing the background noise, we used the measured time-of-flight data of energetic deuterium ions to obtain their energy distribution. We derive the $S$ factor using the measured energy distribution of the ions, the measured volume of the fusion plasma, and the measured fusion yields. This method is model independent in the sense that no assumption on the state of the system is required, but it requires an accurate measurement of the ion energy distribution, especially at high energies, and of the relevant fusion yields. In the ${}^2\mathrm{H}(d,n){}^3\mathrm{He}$ and ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ cases discussed here, it is very important to apply the background subtraction for the energetic ions and to measure the fusion yields with high precision. While the available data on both ion distribution and fusion yields allow us to determine with good precision the $S$ factor in the $d+d$ case (lower Gamow energies), for the $d+{}^3\mathrm{He}$ case the data are not precise enough to obtain the $S$ factor using this method. Our results agree with other experiments within the experimental error, even though smaller values of the $S$ factor were obtained. This might be due to the plasma environment differing from the beam target conditions in a conventional accelerator experiment.

Background: The structure of the semimagic ${}_{50}\mathrm{Sn}$ isotopes were previously studied via measurements of $B(E2;2_1{}^{+}\to 0_1{}^{+}$) and $g$ factors of $2_1{}^{+}$ states. The values of the $B(E2;2_1{}^{+}$) in the isotopes below midshell at $N$ = 66 show an enhancement in collectivity, contrary to predictions from shell-model calculations.

Purpose: This work presents the first measurement of the $2{}_1{}^{+}$ and $4{}_1{}^{+}$ states' magnetic moments in the unstable neutron-deficient ${}^{110}\mathrm{Sn}$. The $g$ factors provide complementary structure information to the interpretation of the observed $B\left(E2\right)$ values.

Methods: The ${}^{110}\mathrm{Sn}$ nuclei have been produced in inverse kinematics in an $\alpha$-particle transfer reaction from ${}^{12}\mathrm{C}$ to ${}^{106}\mathrm{Cd}$ projectiles at 390, 400, and 410 MeV. The $g$ factors have been measured with the transient field technique. Lifetimes have been determined from line shapes using the Doppler-shift attenuation method.

Results: The $g$ factors of the $2_1{}^{+}$ and $4_1{}^{+}$ states in ${}^{110}\mathrm{Sn}$ are $g\left(2_1{}^{+}\right)$ = +0.29(11) and $g\left(4_1{}^{+}\right)$ = +0.05(14), respectively. In addition, the $g\left(4_1{}^{+}\right)$ = +0.27(6) in ${}^{106}\mathrm{Cd}$ has been measured for the first time. A line-shape analysis yielded $\tau {(}^{110}\mathrm{Sn};2_1{}^{+})$ = 0.81(10) ps and a lifetime of $\tau {(}^{110}\mathrm{Sn};3_1{}^{-})$ = 0.25(5) ps was calculated from the fully Doppler-shifted $\gamma$ line.

Conclusions: No evidence has been found in ${}^{110}\mathrm{Sn}$ that would require excitation of protons from the closed $Z=50$ core.

Recently we proposed a reliable method to describe the rotational band in a fully microscopic manner. The method has recourse to the configuration mixing of several cranked mean-field wave functions after the angular-momentum projection. By applying the method with the Gogny D1S force as an effective interaction, we investigate the moments of inertia of the ground state rotational bands in a number of selected nuclei in the rare earth region. As another application we try to describe, for the first time, the two-neutron aligned band in ${}^{164}\mathrm{Er}$, which crosses the ground state band and becomes the yrast states at higher spins. Fairly good overall agreements with the experimental data are achieved; for nuclei, where the pairing correlations are properly described, the agreements are excellent. This confirms that the previously proposed method is really useful for the study of the nuclear rotational motion.

Excited states of the neutron-rich $N=21 {}^{37}\mathrm{S}$ nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of ${}^{36}\mathrm{S}$ ions with a thin ${}^{208}\mathrm{Pb}$ target. The magnetic spectrometer, PRISMA, and the $\gamma$-ray array, CLARA, were used in the measurements. The level scheme of ${}^{37}\mathrm{S}$ was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed $J^{\pi }=(11/2{}^{-})$ level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd $1f_{7/2}$ neutron to the first $2^{+}$ state of the ${}^{36}\mathrm{S}$ core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed.

Two-particle two-hole (2p2h) effect on the Gamow-Teller (GT) transition for neutron-rich nuclei is studied by the second Tamm-Dancoff approximation (STDA) with the Skyrme interaction. Unstable ${}^{24}\mathrm{O}$ and ${}^{34}\mathrm{Si}$ and stable ${}^{48}\mathrm{Ca}$ nuclei are chosen to study the quenching and fragmentation of the GT strengths. Correlation of the 2p2h configurations causes about $20\%$ quenching and downward shift of GT giant resonances (GTGRs). The residual interaction changing relative angular momentum that appeared in the tensor force part gives a meaningful effect to the GT strength distributions. In this work, $17–26\%$ of the total GT strengths are brought to high-energy region above GTGRs. In particular, the tensor force brings strengths to high energy more than 50 MeV. STDA calculation within a small model space for 2p2h configuration is also performed and experimental data of ${}^{48}\mathrm{Ca}$ is reproduced reasonably.

By considering both the effects of the nucleon-nucleon short-range correlations and the isospin-dependent in-medium inelastic baryon-baryon scattering cross section in the transport model, two unrelated Au + Au experimental measurements at 400 MeV/nucleon beam energy are simultaneously analyzed, and a mildly soft symmetry energy ($L\left({\rho }_0\right)=37$ MeV) at supra-saturation densities is obtained. This result is compatible with recent result [Phys. Rev. C 92, 064304 (2015)] shown by comparing the available data on the electric dipole polarizability with the theoretical predictions.

An analysis method is proposed to study the forward-backward (FB) multiplicity fluctuation in high-energy nuclear collisions, built on the earlier work of Bzdak and Teaney [Phys. Rev. C 87, 024906 (2013)]. The method allows the decomposition of the centrality dependence of average multiplicity from the dynamical event-by-event (EbyE) fluctuation of multiplicity in pseudorapidity. Application of the method to AMPT (A Multi-Phase Transport model) and HIJING (Heavy Ion Jet INteraction Generator) models shows that the long-range component of the FB correlation is captured by a few longitudinal harmonics, with the first component driven by the asymmetry in the number of participating nucleons in the two colliding nuclei. The higher-order longitudinal harmonics are found to be strongly damped in AMPT compared to HIJING, due to weaker short-range correlations as well as the final-state effects present in the AMPT model. Two-particle pseudorapidity correlation reveals interesting charge-dependent short-range structures that are absent in HIJING model. The proposed method opens an avenue to elucidate the particle production mechanism and early time dynamics in heavy-ion collisions. Future analysis directions and prospects of using the pseudorapidity correlation function to understand the centrality bias in $p+p, p+\text{A,}$ and $\text{A}+\text{A}$ collisions are discussed.