Differential cross sections for the process $\gamma n\to {\pi }^{-}p$ have been extracted from MAMI-B measurements of $\gamma d\to {\pi }^{-}pp$, accounting for final-state interaction effects, using a diagrammatic technique taking into account the $NN$ and $\pi N$ final-state interaction amplitudes. Results are compared to previous measurements of the inverse process, ${\pi }^{-}p\to n\gamma$, and recent multipole analyses.

The level structure of ${}^{30}$S was studied via the ${}^{28}$Si(${}^3$He,n) and ${}^{32}$S(p,t) reactions at the Nuclear Science Laboratory of the University of Notre Dame and the Research Center for Nuclear Physics of the University of Osaka, Japan. Important experimental information on the energy levels, decay branching ratios, and tentative spin assignments is extracted to calculate the reaction rates for ${}^{29}$P(p,$\gamma$)${}^{30}$S and ${}^{26}$Si($\alpha$,p)${}^{29}$P, which play a critical role in the reaction flow in explosive hydrogen burning.

Core-collapse supernovae may depend sensitively on charged-current neutrino interactions in warm, low-density, neutron-rich matter. A proton in neutron-rich matter is more tightly bound than is a neutron. This energy shift $\Delta U$ increases the electron energy in ${\nu }_e+n\to p+e$, increasing the available phase space and absorption cross section. Likewise $\Delta U$ decreases the positron energy in ${\overline{\nu }}_e+p\to n+e^{+}$, decreasing the phase space and cross section. We have calculated $\Delta U$ using a model-independent virial expansion and we find that $\Delta U$ is much larger, at low densities, than the predictions of many mean-field models. Therefore $\Delta U$ could have a significant impact on charged-current neutrino interactions in supernovae. Preliminary simulations of the accretion phase of core-collapse supernovae find that $\Delta U$ increases ${\overline{\nu }}_e$ energies and decreases the ${\nu }_e$ luminosity.

We present an estimate of the nuclear electric polarizability ${\alpha }_E$ of the ${}^6$He halo nucleus based on six-body microscopic calculations. Wave functions are obtained from semirealistic two-body interactions using the hyperspherical harmonics expansion method. The polarizability is calculated as a sum rule of the dipole response function using the Lanczos algorithm and also by integrating the photoabsorption cross section calculated via the Lorentz integral transform method. We obtain ${\alpha }_E=1.00\left(14\right)$ fm${}^3$, which is much smaller than the published value ${\alpha }_E^{\exp }=1.99\left(40\right)$ fm${}^3$ [Pachucki and Moro, Phys. Rev. A 75, 032521 (2007)] extracted from experimental data. This points toward a potential disagreement between microscopic theories and experimental observations.

Background: Possible evidence for triangular flow and other “higher harmonic flows” in high-energy nucleus-nucleus collisions has received much attention recently. It is conjectured that several higher harmonic flows $v_m$ may result from initial-state geometry fluctuations in $A$-$A$ collisions coupled to a radially expanding medium. However, as with “elliptic flow” $v_2$ measurements, nonhydrodynamic mechanisms such as jet production may contribute to other higher azimuth multipoles $v_m$ as biases.

Purpose: Careful distinctions should be maintained between jet-related and nonjet (possibly hydrodynamic) contributions to $v_m$ (e.g., “nonflow” and “flow”). In this study we consider several questions. (a) To what extent do jetlike structures in two-dimensional (2D) angular correlations contribute to azimuth multipoles inferred from various $v_m$ methods? (b) If a multipole element is added to a 2D fit model, is a nonzero amplitude indicative of a corresponding flow component? (c) Can 2D correlations establish the necessity of nonjet contributions to some or all higher multipoles?

Method: Model fits to 2D angular correlations are used to establish the origins of azimuth multipoles inferred from 1D projections onto azimuth or from nongraphical numerical methods.

Results: We find that jetlike angular correlations, and specifically a 2D peak at the angular origin consistent with jet production, constitute the dominant contribution to inferred higher multipoles, and the data do not require higher multipoles in isolation from the jetlike 2D peak.

Conclusions: The inference of “higher harmonic flows” results from identifying certain nominally jetlike structures as flow manifestations through unjustified application of 1D Fourier series analysis. Although the peak structure at the angular origin is strongly modified in more-central collisions, some properties remain compatible with relevant pQCD theory expectations for jet production.

We show that in hydrodynamic simulations for relativistic heavy-ion collisions, strong resonance decay calculations can be performed with fewer species of particle resonances while preserving good accuracy in single particle spectra and flow anisotropies. Such partial resonance calculations boost computation efficiency by a factor of 10 which is essential for large scale event-by-event simulations.

Excited states in ${}^{150}$Nd have been investigated with the ${}^{150}$Nd($n$,$n$${}^{\prime }\gamma$) reaction. In addition to the previously known $K^{\pi }$ $=$ 0${}^{-}$ band, a new $K^{\pi }$ $=$ 2${}^{-}$ band is established, and level lifetimes are determined for all the reported band members. These lifetime data reveal a pattern of enhanced $E1$ transition strengths, similar to that observed in ${}^{152}$Sm and unprecedented in other nuclei, thus suggesting a systematic pattern for octupole collectivity in the $N$ $=$ 90 isotones. The pattern lies outside of the various model descriptions that have been put forward for nuclei in this or any other region.

The $\alpha$-decay chains originating from the $\pi s_{1/2}$ and $\pi h_{11/2}$ states in ${}^{173}$Au have been investigated following fusion-evaporation reactions. Four generations of $\alpha$ radioactivities have been correlated with ${}^{173}$Au${}^m$ leading to a measurement of the $\alpha$ decay of ${}^{161}$Ta${}^m$. It has been found that the known $\alpha$ decay of ${}^{161}$Ta, which was previously associated with the decay of the ground state, is in fact the decay of an isomeric state. This work also reports on the first observation of prompt $\gamma$ rays feeding the ground state of ${}^{173}$Au. This prompt $\gamma$ radiation was used to aid the study of the $\alpha$-decay chain originating from the $\pi s_{1/2}$ state in ${}^{173}$Au. Three generations of $\alpha$ decays have been correlated with this state, leading to the observation of a previously unreported activity which is assigned as the decay of ${}^{165}$Re${}^g$. This work also reports the excitation energy of an $\alpha$-decaying isomer in ${}^{161}$Ta and the $Q_{\alpha }$ value of the decay of ${}^{161}$Ta${}^g$.

We use the $2\alpha$ cluster model to describe the properties of ${}^8$Be. The $E2$ transitions in a two-body continuum can be described as bremsstrahlung in an inelastic scattering process. We compute cross sections as functions of initial energy for the possible $E2$ transitions from initial angular momenta of $0^{+},2^{+},4^{+},6^{+},\text{and}{8}^{+}$. The dependence on the exact shape of potentials is very small when the low-energy scattering phase shifts are the same. We relate to practical observables where energies of the emerging $\alpha$ particles are restricted in various ways. The unphysical infrared contribution is removed. We find pronounced peaking for photon energies matching resonance positions. Contributions from intraband transitions are rather small although substantial (and even dominating) for initial energies between resonances. Structure information is derived but both ${\mathcal{B}}^{\left(E2\right)}$ transition strength values and electromagnetic transition rates are ambiguous in the continuum.

We review the currently available formalisms for radiative energy loss of a high-momentum parton in a dense strongly interacting medium. The underlying theoretical framework of the four commonly used formalisms is discussed and the differences and commonalities between the formalisms are highlighted. A quantitative comparison of the single-gluon emission spectra as well as the energy-loss distributions is given for a model system consisting of a uniform medium with a fixed length of $L=2$ fm and $L=5$ fm (the “Brick”). Sizable quantitative differences are found. The largest differences can be attributed to specific approximations that are made in the calculation of the radiation spectrum.

The appearance of monojets is among the most striking signature of jet quenching in the context of ultrarelativistic heavy-ion collisions at the Large Hadron Collider. Experimentally, the asymmetry of back-to-back jets is quantified in terms of the dijet imbalance distribution by the ATLAS and CMS collaborations. The CMS collaboration has also studied the trigger jet momentum ($P_T$) dependence of the imbalance in the range between 120 and 500 GeV, which is found to decrease with jet $P_T$. In this Rapid Communication, results from the in-medium shower code YaJEM are compared with this data. These suggest that the main effects observed in the data are the kinematical collimation of jets and the increase in the probability to produce quark jets with jet $P_T$, whereas there is no indication for any nontrivial energy dependence of the shower-medium interaction mechanism itself. The data furthermore can rule out models in which the jet shape is collimated owing to the medium modification.

The study of the ${}^{48}$Ca+${}^{249-252}$Cf reactions in a wide energy interval around the external barrier has been achieved with the aim of investigating the dynamical effects of the entrance channel via the ${}^{48}$Ca induced reactions on the ${}^{249–252}$Cf targets and to analyze the influence of odd and even neutron composition in target on the capture, quasifission, and fusion cross sections. Moreover, we also present the results of the individual evaporation residue excitation functions obtained from the de-excitation cascade of the various even-odd and even-even ${}^{297–300}$118 superheavy compound nuclei reached in the studied reactions, and we compare our results of the ${}^{294}$118 evaporation residue yields obtained in the synthesis process of the ${}^{48}$Ca+${}^{249,250}$Cf reactions with the experimental data obtained in the ${}^{48}$Ca+${}^{249}$Cf experiment carried out at the Flerov Laboratory of Nuclear Reactions of Dubna.

For stars with 0.8 M${}_{\odot }$ $\le$ M $\le$ 8.0 M${}_{\odot }$, nucleosynthesis enters its final phase during the asymptotic giant branch (AGB) stage. During this evolutionary period, grain condensation occurs in the stellar atmosphere, and the star experiences significant mass loss. The production of presolar grains can often be attributed to this unique stellar environment. A subset of presolar oxide grains features dramatic ${}^{18}$O depletion that cannot be explained by the standard AGB star burning stages and dredge-up models. An extra mixing process, referred to as cool bottom processing (CBP), was proposed for low-mass AGB stars. The ${}^{18}$O depletion observed within certain stellar environments and within presolar grain samples may result from the ${}^{18}$O+$p$ processes during CBP. We report here on a study of the ${}^{18}$O($p$,$\gamma$)${}^{19}$F reaction at low energies. Based on our new results, we found that the resonance at $E_{\mathrm{R}}^{\mathrm{lab}}=95$ keV has a negligible affect on the reaction rate at the temperatures associated with CBP. We also determined that the direct capture $S$ factor is almost a factor of 2 lower than the previously recommended value at low energies. An improved thermonuclear reaction rate for ${}^{18}$O($p$,$\gamma$)${}^{19}$F is presented.

We present a new, fast algorithm and computing code developed to efficiently calculate the two-body matrix elements (TBMEs) of the neutrinoless double-beta decay transition operator, which are necessary for the shell model calculation of the double-beta decay matrix elements in the closure approximation. The improvement consists of a rearrangement of the expression of the TBMEs that allows us to do the radial integrals analytically, and thus only the integration over the momentum remains to be performed numerically. This fast algorithm is an important step forward in investigating quenching effects of the transition operator by considering their evolution in increasingly larger shell model spaces.

High-spin states in ${}^{123}$I were populated in the reaction ${}^{80}$Se(${}^{48}$Ca,$p4n$)${}^{123}$I at a beam energy of 207 MeV and $\gamma$-ray coincidence events were measured using the Gammasphere spectrometer. Three weakly populated, high-spin rotational bands have been discovered with characteristics similar to those of the long collective bands recently observed in other nuclei of this mass region. Configuration assignments are proposed based on calculations within the framework of the cranked Nilsson-Strutinsky approach.

As part of a program to study odd-$A$ nuclei in the Hartree-Fock-Bogoliubov (HFB) theory, we have developed a new calculational tool to find the HFB minima of odd-$A$ nuclei based on the gradient method and using interactions of Gogny's form. The HFB minimization includes both time-even and time-odd fields in the energy functional, avoiding the commonly used “filling approximation”. Here we apply the method to calculate neutron pairing gaps in some representative isotope chains of spherical and deformed nuclei, namely the $Z=8,50$, and 82 spherical chains and the $Z=62$ and 92 deformed chains. We find that the gradient method is quite robust, permitting us to carry out systematic surveys involving many nuclei. We find that the time-odd field does not have large effect on the pairing gaps calculated with the Gogny D1S interaction. Typically, adding the $T$-odd field as a perturbation increases the pairing gap by 100 keV, but the re-minimization brings the gap back down. This outcome is very similar to results reported for the Skyrme family of nuclear energy density functionals. Comparing the calculated gaps with the experimental ones, we find that the theoretical errors have both signs implying that the D1S interaction has a reasonable overall strength. However, we find some systematic deficiencies comparing spherical and deformed chains and comparing the lighter chains with the heavier ones. The gaps for heavy spherical nuclei are too high, while those for deformed nuclei tend to be too low. The calculated gaps of spherical nuclei show hardly any $A$ dependence, contrary to the data. Inclusion of the $T$-odd component of the interaction does not change these qualitative findings.

A phenomenological $pn\to pp{\pi }^{-}$ model of $A(p,{\pi }^{-})B$ reactions is developed that incorporates the spin dependence of the former reaction. The model development follows closely that of the $pp\to d{\pi }^{+}$ model for $A(p,{\pi }^{+})C$ reactions. Predictions of the analyzing powers and differential cross sections for the $(p,{\pi }^{-})$ reaction on ${}^{13}$C at 200 MeV are presented and discussed. Calculated differential cross sections describe reasonably well the shape of the experimental data, although the predicted strengths vary considerably. Model predictions of the analyzing powers are in general agreement with the data. Nuclear structure amplitudes are obtained from a no-core multi-$\hslash \omega$ shell model. Sensitivities of the observables to the nuclear structure details and also the amplitudes of the primary $pn\to pp{\pi }^{-}$ reaction are investigated.

We postulate that the Fermi function should be derived from the amplitude, not from the solution of the Dirac equation, in quantum field theory. Then, we obtain the following results: (1) We give the amplitude and width of the neutron $\beta$ decay, $n\to p+e^{-}+{\overline{\nu }}_e$, to the first order in $\alpha$. We evaluate it using Feynman parameters. (2) As the result, we confirm the terms, which can be interpreted as the Fermi function expanded to order $\alpha$. (3) We give the same result using the contour integral. (4) We check that there are no such terms in a similar process, ${\overline{\nu }}_e+p\to e^{+}+n$. (5) We perform the Fermi function expanded to the second order in $\alpha$ using contour integral. (6) The conventional Fermi function affects the convergence of perturbation theory.

Previous work on neutrino emission from proto-neutron stars which employed full solutions of the Boltzmann equation showed that the average energies of emitted electron neutrinos and antineutrinos are closer to one another than predicted by older, more approximate work. This in turn implied that the neutrino driven wind is proton rich during its entire life, precluding $r$-process nucleosynthesis and the synthesis of Sr, Y, and Zr. This work relied on charged-current neutrino interaction rates that are appropriate for a free nucleon gas. Here, it is shown in detail that the inclusion of the nucleon potential energies and collisional broadening of the response significantly alters this conclusion. Isovector interactions, which give rise to the nuclear symmetry energy, produce a difference between the neutron and proton single-particle energies $\Delta U=U_n-U_p$ and alter the kinematics of the charged-current reactions. In neutron-rich matter, and for a given neutrino/antineutrino energy, the rate for ${\nu }_e+n\to e^{-}+p$ is enhanced while ${\overline{\nu }}_e+p\to n+e^{+}$ is suppressed because the $Q$ value for these reactions is altered by $\pm \Delta U$, respectively. In the neutrino decoupling region, collisional broadening acts to enhance both ${\nu }_e$ and ${\overline{\nu }}_e$ cross sections, and random-phase approximation (RPA) corrections decrease the ${\nu }_e$ cross section and increase the ${\overline{\nu }}_e$ cross section, but mean field shifts have a larger effect. Therefore, electron neutrinos decouple at lower temperature than when the nucleons are assumed to be free and have lower average energies. The change is large enough to allow for a reasonable period of time when the neutrino driven wind is predicted to be neutron rich. It is also shown that the electron fraction in the wind is influenced by the nuclear symmetry energy.