Elastic pion-nucleon scattering is analyzed in the framework of chiral perturbation theory up to fourth order within the heavy-baryon expansion and a covariant approach based on an extended on-mass-shell renormalization scheme. We discuss in detail the renormalization of the various low-energy constants and provide explicit expressions for the relevant $\beta$ functions and the finite subtractions of the power-counting breaking terms within the covariant formulation. To estimate the theoretical uncertainty from the truncation of the chiral expansion, we employ an approach which has been successfully applied in the most recent analysis of the nuclear forces. This allows us to reliably extract the relevant low-energy constants from the available scattering data at low energy. The obtained results provide clear evidence that the breakdown scale of the chiral expansion for this reaction is related to the $\mathrm{\Delta }$ resonance. The explicit inclusion of the leading contributions of the $\mathrm{\Delta }$ isobar is demonstrated to substantially increase the range of applicability of the effective field theory. The resulting predictions for the phase shifts are in an excellent agreement with the predictions from the recent Roy–Steiner-equation analysis of pion-nucleon scattering.

The Vlasov formalism is extended to relativistic mean field hadron models with nonlinear terms up to fourth order and applied to the calculation of the crust-core transition density. The effect of the nonlinear $\omega \rho$ and $\sigma \rho$ coupling terms on the crust-core transition density and pressure and on the macroscopic properties of some families of hadronic stars is investigated. For that purpose, six families of relativistic mean field models are considered. Within each family, the members differ in the symmetry energy behavior. For all the models, the dynamical spinodals are calculated, and the crust-core transition density and pressure and the neutron star mass-radius relations are obtained. The effect on the star radius of the inclusion of a pasta calculation in the inner crust is discussed. The set of six models that best satisfy terrestrial and observational constraints predicts a radius of $13.6\pm 0.3$ km and a crust thickness of $1.36\pm 0.06$ km for a $1.4M_{\odot }$ star.

We present an analysis of dihadron correlations using recently developed methods for background subtraction which allow for higher precision measurements with fewer assumptions about the background. These studies indicate that low momentum jets interacting with the medium do not equilibrate with the medium but rather that interactions with the medium lead to more subtle increases in their widths and fragmentation functions, consistent with observations from studies of higher momentum fully reconstructed jets. The away-side shape is not consistent with a Mach cone. The qualitatively different conclusions reached with a more careful consideration of the background subtraction call into question the complete suppression of jets in central collisions observed in earlier studies, indicating that this is also an artifact of the background subtraction.

Background: The configuration-interaction approach to nuclear structure uses the effective Hamiltonian in a finite orbital space. The various parts of this Hamiltonian and their interplay are responsible for specific features of physics including the shape of the mean field and level density. This interrelation is not sufficiently understood.

Purpose: We intend to study phase transitions between spherical and deformed shapes driven by different parts of the nuclear Hamiltonian and to establish the presence of the collective enhancement of the nuclear level density by varying the shell-model matrix elements.

Method: By varying the interaction matrix elements we define, for nuclei in the $sd$ and $pf$ shells, the sectors with spherical and deformed shapes. By using the moments method that does not require the full diagonalization we relate the shape transitions with the corresponding level density.

Results: Enhancement of the level density in the low-energy part of the spectrum is observed in clear correlation with a deformation phase transition induced mainly by the matrix elements of single-particle transfer.

Conclusions: The single-particle-transfer matrix elements in the shell model nuclear Hamiltonian are indeed the carriers of deformation, providing rotational observables and enhanced level densities.

Background: The ${}^{16}\mathrm{O}(e,e^{\prime }p)$ reaction in the quasielastic region has been studied in several experiments to determine spectroscopic factors, hence, the degree to which ${}^{16}\mathrm{O}$ looks like a closed shell. By varying the kinematics, experimentalists are able to extract response functions which comprise the cross section. However, analysis of the response functions separately produces very different spectroscopic factors. Two calculations led to different conclusions as to whether exchange currents can eliminate the discrepancies. Neither calculation considered relativistic corrections.

Purpose: The purpose of the article is to investigate the disagreement as to whether exchange currents are the solution to obtaining consistent spectroscopic factors and to show that relativistic corrections have a much greater influence on providing this consistency.

Methods: This calculation employs the recoil corrected continuum shell model, a model that uses a realistic interaction and produces nonspurious scattering states that are solutions to the coupled-channel problems. Pionic and pair contributions to the exchange currents were calculated as developed by Dubach et al. [Nucl. Phys. A 271, 279 (1976)]. Relativistic effects are included by use of the direct Pauli reduction.

Results: Contributions of the exchange currents are shown to be insufficient to provide consistent spectroscopic factors. However, the inclusion of relativistic corrections produces spectroscopic factors from the different responses and cross sections which are very similar for both the $p_{1/2}$ and the $p_{3/2}$ states and both the $\left(\left|\mathbf{q}\right|,\omega \right)=\left(460\mathrm{MeV}/\mathrm{c},100\mathrm{MeV}\right)$ and $\left(\left|\mathbf{q}\right|,\omega \right)=\left(570\mathrm{MeV}/\mathrm{c},172\mathrm{MeV}\right)$ data. The influence of channel coupling is also shown to be significant. Tests of current conservation show that inclusion of the direct Pauli reduction produces small increases in its violation.

Conclusions: Results are model dependent. Meson-exchange current contributions are not sufficient. Relativistic corrections can be large and lead to more consistent spectroscopic factors. Contributions from channels other than the outgoing channels can be significant. Response functions which depend on the transverse current are sensitive to the lower component of relativistic wave functions and, hence, would provide a measure of the appropriateness of any relativistic model.

We present measurements of the near side of triggered di-hadron correlations using neutral strange baryons $(\mathrm{\Lambda },\overline{\mathrm{\Lambda }})$ and mesons $\left(K_S^0\right)$ at intermediate transverse momentum $(3 < p_T <6 \mathrm{GeV}/c)$ to look for possible flavor and baryon-meson dependence. This study is performed in $d+\mathrm{Au}$, Cu+Cu, and Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations from jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.

We study the near-threshold incoherent $\varphi$ photoproduction on the deuteron based on a model of $\gamma N\to \varphi N$, consisting of Pomeron, $(\pi ,\eta )$ exchanges, and a $J^P=3/2^{-}$ resonance, which describes the low-energy $\gamma p\to \varphi p$ LEPS data well, including the peak in the forward differential cross section. The calculation is done up to double rescatterings, with the spin dependence of the elementary $\gamma N\to \varphi N$ amplitude retained throughout the calculation. The Fermi motion and final-state interactions (FSIs) are all properly treated as prescribed by realistic nucleon-nucleon interaction. The couplings of the resonance to $\gamma n$ and $\varphi n$ channels are estimated with the help of a constituent quark model. The main features of the LEPS and CLAS data are described reasonably well except for some quantitative discrepancies at very low energies and low-momentum-transfer regions. It is found that contributions of Fermi motion, $pn$ FSI, and resonance are all indispensable in bridging the differences between the single-scattering results and the data. The off-shell rescattering is found to be important because it cancels out a large portion of the on-shell contribution. The discrepancies at low-momentum-transfer regions might be related to the binning size of the data. No peak is found to be associated with the weak resonance because it gets smeared out by the Fermi motion and FSI with the deuterium target. The problem at very-low-energy regions hints at the possible contributions from other mechanisms and should be investigated in depth with the use of recent high-statistics $\gamma p\to \varphi p$ data from CLAS.

We present a phenomenological study of nuclear effects in neutrino charged-current interactions, using transverse kinematic imbalances in exclusive measurements. Novel observables with minimal dependence on neutrino energy are proposed to study quasielastic scattering and especially resonance production. They should be able to provide direct constraints on nuclear effects in neutrino- and antineutrino-nucleus interactions.

We investigate the effect of strong magnetic fields on the adiabatic radial oscillations of hadronic stars. We describe magnetized hadronic matter within the framework of the relativistic nonlinear Walecka model and integrate the equations of relativistic radial oscillations to determine the fundamental pulsation mode. We consider that the magnetic field increases, in a density dependent way, from the surface, where it has a typical magnetar value of ${10}^{15}\mathrm{G}$, to the interior of the star, where it can be as large as $3\times {10}^{18}\mathrm{G}$. We show that magnetic fields of the order of ${10}^{18}\mathrm{G}$ at the stellar core produce a significant change in the frequency of neutron star pulsations with respect to unmagnetized objects. If radial pulsations are excited in magnetar flares, they can leave an imprint in the flare lightcurves and open a new window for the study of highly magnetized ultradense matter.

A model describing nuclear collisions at intermediate energies is presented and the results are compared with recently measured double differential cross sections in C-C reactions at 95 MeV/nucleon. Results show the key role played by geometrical effects and the memory of the entrance channel, in particular the momentum distributions of the two incoming nuclei. Special attention is paid to the description of processes occurring at midrapidity. To this end, a random particle production mechanism by means of a coalescence process in velocity space is considered in the overlap region of the two interacting nuclei.

A linearized Boltzmann transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the momentum and temperature dependences of the transport coefficients, and the radial flow of the expanding fireball. Our model calculations show good descriptions of the $D$ meson suppression and elliptic flow observed at the Larege Hadron Collider and the Relativistic Heavy-Ion Collider. The prediction for the Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV is provided.

We investigate the impact of pairing correlations on neutrino transport in stellar matter. Our analysis is extended to nuclear matter conditions where large density fluctuations may develop, associated with the onset of the liquid-vapor phase transition, and where clustering phenomena occur. Within a thermodynamical treatment, we show that at moderate temperatures, where pairing effects are still active, the scattering of neutrinos in the nuclear medium is significantly affected by pairing correlations, which increase the neutrino trapping, thus modifying the cooling mechanism, by neutrino emission, of protoneutron stars.

The breakup reaction ${}^9\mathrm{Be}({}^4\mathrm{He},3\alpha )\mathit{n}$ was measured using an array of four double-sided silicon strip detectors at beam energies of 22 and 26 MeV. Excited states in ${}^9\mathrm{Be}$ up to 8 MeV were populated and reconstructed through measurements of the charged reaction products. Evidence is given for a state in ${}^9\mathrm{Be}$ at $3.{82}_{\text{-0.09}}^{\text{+0.08}}$ MeV with $\mathrm{\Gamma }={1240}_{\text{-90}}^{\text{+270}}$ keV. This is consistent with two recent measurements of a state with similar properties in the mirror nucleus ${}^9\mathrm{B}$. An analysis of the reduced widths (${}^8\mathrm{Be}_{\mathrm{g}.\mathrm{s}.}$ channel) of this state along with the proposed mirror state has led to a firm limit of $J\le 7/2$ and a tentative assignment of $J^{\pi }=1/2^{-}$ or $3/2^{-}$.

The dynamical cluster decay model (DCM) is applied to understand the dynamics of ${}^{48}\mathrm{Ca}+{}^{238}\mathrm{U},{}^{244}\mathrm{Pu},{}^{248}\mathrm{Cm}$ reactions at comparable excitation energies across the barrier. To understand the capture stage of ${}^{286}112^{*},{}^{292}114^{*}$, and ${}^{296}116^{*}$ nuclei, the compound nucleus formation probability is calculated. The indication of $P_{CN}<1$ in the DCM framework demonstrates the fact that some competing process such as quasifission may occur at the capture stage of the ${}^{48}\mathrm{Ca}$ induced reactions. To understand this further, the comparative decay analysis of ${}^{286}112^{*},{}^{292}114^{*}$ and ${}^{296}116^{*}$, nuclei is carried out using ${\beta }_{2i}$ deformations within hot optimum orientation criteria, and the calculated fission cross sections find nice agreement with available data. The fission mass distribution shows a double humped structure where a symmetric peak observed around the Sn region appears to find its genesis in a symmetric quasifission component. On the other hand, the emergence of peaks around Pb in the decay of $Z=112$, 114, and 116 nuclei signify the possible presence of asymmetric quasifission. Higher and broader asymmetric quasifission peaks are observed for ${}^{296}116^{*}$ and ${}^{292}114^{*}$ nuclei as compared to ${}^{286}112^{*}$ nucleus. Beside this, the total kinetic energy (TKE) distribution of the decay fragments is also explored by using different proximity potentials, such as Prox-77, Prox-88, and Prox-00. Prox-88 seems to perform better and the calculated TKE values find relatively better comparison at lower angular momentum states. The possible role of different radii of the decaying nuclei is also exercised to understand the $\overline{\mathrm{TKE}}$ dynamics of ${}^{48}\mathrm{Ca}+{}^{238}\mathrm{U},{}^{244}\mathrm{Pu},{}^{248}\mathrm{Cm}$ reactions.

The decay widths of four-body double-pion decays $d^{*}\to pn{\pi }^0{\pi }^0,d^{*}\to pn{\pi }^{+}{\pi }^{-}$, and isoscalar parts of $d^{*}\to pp{\pi }^0{\pi }^{-}$ and $d^{*}\to nn{\pi }^{+}{\pi }^0$ are explicitly calculated with the help of the $d^{*}$ wave function obtained in a chiral SU(3) quark model calculation. The effect of the dynamical structure on $d^{*}$'s width is analyzed both in the single $\mathrm{\Delta }\mathrm{\Delta }$ channel and the $\mathrm{\Delta }\mathrm{\Delta }+CC$ coupled-channel approximations. It is found that in the latter case, the obtained partial decay widths of $d^{*}\to pn{\pi }^0{\pi }^0,d^{*}\to pn{\pi }^{+}{\pi }^{-}$, and those of $d^{*}$ to the isoscalar parts of $pp{\pi }^0{\pi }^{-}$ and $nn{\pi }^{+}{\pi }^0$ are about $9.6\mathrm{MeV},20.6\mathrm{MeV},3.5\mathrm{MeV}$ and $3.5\mathrm{MeV}$, respectively. As a consequence, the total width is about $71.9\mathrm{MeV}$. These widths are consistent with our previous estimation by using cross section data and observed width. Apparently, the resultant mass and width in the $\mathrm{\Delta }\mathrm{\Delta }+CC$ coupled-channel calculation again support our assertion that the $d^{*}$ resonance is a six-quark dominated exotic state.

The volume and surface components of the nuclear symmetry energy (NSE) and their ratio are calculated within the coherent density fluctuation model (CDFM). The estimations use the results of the model for the NSE in finite nuclei based on the Brueckner energy-density functional for nuclear matter. In addition, we present results for the NSE and its volume and surface contributions obtained by using the Skyrme energy-density functional. The CDFM weight function is obtained using the proton and neutron densities from the self-consistent HF+BCS method with Skyrme interactions. We present and discuss the values of the volume and surface contributions to the NSE and their ratio obtained for the Ni, Sn, and Pb isotopic chains, studying their isotopic sensitivity. The results are compared with estimations of other approaches which have used available experimental data on binding energies, neutron-skin thicknesses, excitation energies to isobaric analog states (IAS), and also with results of other theoretical methods.

A ${}^{52}\mathrm{Cr}(p,t){}^{50}\mathrm{Cr}$ two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in ${}^{50}\mathrm{Cr}$ were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited $0^{+}$ state was found. As a result, the $0_2^{+}$ state is reassigned at an excitation energy of $E_x=3895.0\left(5\right)$ keV in ${}^{50}\mathrm{Cr}$. This reassignment directly impacts direct searches for a nonanalog Fermi ${\beta }^{+}$ decay branch in ${}^{50}\mathrm{Mn}$. These results also show better systematic agreement with the theoretical predictions for the $0^{+}$ state spectrum in ${}^{50}\mathrm{Cr}$ using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to ab-initio shell-model predictions using the IM-SRG formalism based on $NN$ and $3N$ forces from chiral-EFT in the $pf$-shell for the first time.

The doubly-odd nucleus ${}^{136}\mathrm{La}$ is theoretically studied in terms of a large-scale shell model. The energy spectrum and transition rates are calculated and compared with the most updated experimental data. The isomerism is investigated for the first ${14}^{+}$ state, which was found to be an isomer in the previous study [Phys. Rev. C 91, 054305 (2015)]. It is found that the ${14}^{+}$ state becomes an isomer due to a band crossing of two bands with completely different configurations. The yrast band with the ($\nu h_{11/2}^{-1}\otimes \pi h_{11/2}$) configuration is investigated, revealing a staggering nature in $M1$ transition rates.

To investigate the dependence of giant dipole resonance (GDR) width on temperature $\left(T\right)$ and angular momentum $\left(J\right)$, high energy $\gamma$-ray spectra were measured in the reaction ${}^{28}\mathrm{Si}+{}^{124}\mathrm{Sn}$ at $E_{{}^{28}\mathrm{Si}}=135$ MeV. The $J$ information was deduced from multiplicity of low-energy $\gamma$ rays. The GDR parameters, namely, the centroid energy and width are extracted using statistical model analysis. The observed variation of the GDR width for $T\sim 1.2$–1.37 MeV and $J\sim 20\hslash$–$40\hslash$ is consistent with the universal scaling given by Kusnezov et al., which is applicable in the liquid-drop regime. The GDR input cross sections extracted from the statistical model best fits are compared with thermal shape fluctuation model (TSFM) calculations and are found to be in good agreement. The TSFM calculations predominantly favor the noncollective oblate shape, while the statistical model fit with both prolate and oblate shapes describes the data. The present data together with earlier measurements indicate a very slow variation of the GDR width for $T\sim 1.2$ to 1.5 MeV. The observed trend is well explained by the TSFM calculations, although the calculated values are $\sim 4$%–13% higher than the data.

A model to calculate particle-induced reaction cross sections with statistical Hauser-Feshbach theory including direct reactions is given. The energy average of the scattering matrix from the coupled-channels optical model is diagonalized by the transformation proposed by Engelbrecht and Weidenmüller [C. A. Engelbrecht and H. A. Weidenmüller, Phys. Rev. C 8, 859 (1973)]. The ensemble average of $S$-matrix elements in the diagonalized channel space is approximated by a model of Moldauer [P. A. Moldauer, Phys. Rev. C 12, 744 (1975)] using the newly parametrized channel degree-of-freedom ${\nu }_a$ to better describe the Gaussian orthogonal ensemble (GOE) reference calculations. The Moldauer approximation is confirmed by a Monte Carlo study using a randomly generated $S$ matrix, as well as the GOE threefold integration formula. The method proposed is applied to the ${}^{238}\mathrm{U}\left(n,n^{\prime }\right)$ cross-section calculation in the fast-energy range, showing an enhancement in the inelastic scattering cross sections.