Effects of an external magnetic field on various properties of quantum chromodynamics (QCD) matter under extreme conditions of temperature and density (chemical potential) have been analyzed. To this end, we use SU(3) Polyakov $\text{linear}-\sigma$ model and assume that the external magnetic field $\left(eB\right)$ adds some restrictions to the quarks' energy due to the existence of free charges in the plasma phase. In doing this, we apply the Landau theory of quantization, which assumes that the cyclotron orbits of charged particles in a magnetic field should be quantized. This requires an additional temperature to drive the system through the chiral phase transition. Accordingly, the dependence of the critical temperature of chiral and confinement phase transitions on the magnetic field is characterized. Based on this, we have studied the thermal evolution of thermodynamic quantities (energy density and trace anomaly) and the first four higher-order moment of particle multiplicity. Having all these calculations, we have studied the effects of the magnetic field on the chiral phase transition. We found that both critical temperature $T_c$ and critical chemical potential increase with increasing magnetic field, $eB$. Last but not least, the magnetic effects of the thermal evolution of four scalar and four pseudoscalar meson states are studied. We concluded that the meson masses decrease as the temperature increases up to $T_c$. Then, the vacuum effect becomes dominant and rapidly increases with the temperature $T$. At low $T$, the scalar meson masses normalized to the lowest Matsubara frequency rapidly decrease as $T$ increases. Then, starting from $T_c$, we find that the thermal dependence almost vanishes. Furthermore, the meson masses increase with increasing magnetic field. This gives a characteristic phase diagram of $T$ vs external magnetic field $eB$. At high $T$, we find that the masses of almost all meson states become temperature independent. It is worthwhile to highlight that the various meson states likely have different critical temperatures.

The pole structure of the current George Washington University (GWU-SAID) partial-wave analysis of elastic $\pi N$ scattering and $\eta N$ production data is studied. Pole positions and residues are extracted from both the energy-dependent and single-energy fits, using two different methods. For the energy-dependent fits, both contour integration and a Laurent + Pietarinen approach are used. In the case of single-energy fits, the Laurent+Pietarinen approach is used. Errors are estimated and the two sets of results are compared to other fits to data.

The stability of magnetized strange quark matter (MSQM) is studied in the MIT bag model with the density dependent bag pressure. In the consistent thermodynamic description of MSQM, the quark chemical potentials, the total thermodynamic potential, and the anisotropic pressure acquire the corresponding additional term proportional to the density derivative of the bag pressure. The model parameter space is determined for which MSQM is absolutely stable, i.e., its energy per baryon is less than that of the most stable ${}^{56}\mathrm{Fe}$ nucleus under zero external pressure and vanishing temperature. It is shown that there exists a magnetic field strength $H_{umax}$ at which the upper bound $B_{\infty }^u$ on the asymptotic bag pressure $B_{\infty }\equiv B({\varrho }_B\gg {\varrho }_0)$ $({\varrho }_0$ being the nuclear saturation density) from the absolute stability window vanishes. The value of this field, $H_{umax}\sim (1–3)\times {10}^{18}$ G, represents the upper bound on the magnetic field strength, which can be reached in a strongly magnetized strange quark star. It is clarified how the absolute stability window and upper bound on the magnetic field strength are affected by varying the parameters in the Gaussian parametrization for the density dependence of the bag pressure.

We study the fusion reaction of light systems with one-dimensional barrier penetration model using the $\alpha \text{−}\alpha$ double-folding cluster (DFC) potential. We especially analyze the fusion cross sections of the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C},{}^{16}\mathrm{O},{}^{24}\mathrm{Mg},{}^{28}\mathrm{Si},{}^{16}\mathrm{O}+{}^{16}\mathrm{O},{}^{24}\mathrm{Mg}+{}^{24}\mathrm{Mg},{}^{28}\mathrm{Si}$, and ${}^{28}\mathrm{Si}+{}^{28}\mathrm{Si}$ reactions. The results are compared with the one obtained with M3Y double folding (DFM) and the Akyüz-Winther (A-W) potentials. It is found that the calculations with DFM and DFC potentials can reproduce the experimental data much better than the calculations using the A-W potential. We also carried out an analysis on the astrophysical aspect of the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C},{}^{16}\mathrm{O}$, and ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ reactions. The calculations using DFC and DFM potentials could fit the $S$-factor data reasonably well. However, the calculated reaction rates are lower than the compilation of Caughlan and Fowler at low temperatures. In the important range of temperatures in stellar evolution, the DFC potential reproduces very satisfactory fitting to the experimental cross section and the $S$-factor data and gives a consistent prediction of astrophysical reaction rates. This finding indicates that the DFC potential could be used as an alternative potential to study the fusion reactions in the astrophysical interest.

We study the impact of three-body forces on the response functions of cold neutron matter. These response functions are determined in the random phase approximation from a residual interaction expressed in terms of Landau parameters. Special attention is paid to the noncentral part, including all terms allowed by the relevant symmetries. Using Landau parameters derived from realistic nuclear two- and three-body forces grounded in chiral effective field theory, we find that the three-body term has a strong impact on the excited states of the system and in the static and long-wavelength limit of the response functions for which a new exact formula is established.

Reaction cross sections of ${}^8\mathrm{Li}$ on stable targets were measured at intermediate energies. With the existing experimental data of interaction cross sections at 790 MeV/nucleon the nucleon density distribution of ${}^8\mathrm{Li}$ was extracted by the use of the modified Glauber model. Meanwhile, the existing data of ${}^8\mathrm{B}$ have been also reanalyzed. Structures of ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ were compared through the density. On the basis of dilute surface densities, the discussion of ${}^7\mathrm{Li}\left(n,\gamma \right){}^8\mathrm{Li}$ and ${}^7\mathrm{Be}\left(p,\gamma \right){}^8\mathrm{B}$ capture reactions was performed within the framework of the direct capture reaction mechanism. The calculations agreed quite well with the experimental data as well as other analyses.

Background: The isobaric yield ratio difference (IBD) between reactions is know to be sensitive to the density difference between projectiles in heavy-ion collisions around the Fermi energy.

Purpose: The target effects in the isobaric yield ratio (IYR) and the IBD results have been studied.

Methods: The amount of isotopes in the $140A$ MeV ${}^{48,40}\mathrm{Ca}+{}^{181}\mathrm{Ta}{/}^9\mathrm{Be}$ and ${}^{58,64}\mathrm{Ni}+{}^{181}\mathrm{Ta}{/}^9\mathrm{Be}$ reactions have been previously measured with high accuracy. The IYR and IBD results have been obtained from these reactions to study the effects of the light ${}^9\mathrm{Be}$ and heavy ${}^{181}\mathrm{Ta}$ targets. A ratio ($r_{\Delta \mu }$) between the IBD results for the reactions with Ta and Be targets is defined to quantitatively show the target dependence of the IBD results. Results The IYRs for reactions with symmetric projectiles are more easily affected than those for reactions with neutron-rich projectiles. The IBD results are suppressed by using the ${}^{181}\mathrm{Ta}$ target to different degrees.

Conclusions: The IYR and IBD results are influenced by the target used. The IBD for the $I=1$ isobaric chain is suggested as a probe to study the difference between the neutron and proton densities of the reaction systems.

We compute the photon emission rate from a quark-gluon plasma with an anisotropic particle momentum distribution induced by a nonvanishing local shear pressure tensor. Our calculation includes photon production through Compton scattering and quark-antiquark annihilation at leading order in ${\alpha }_s$, with all off-equilibrium corrections to leading order in the momentum anisotropy. For fermions we prove that the Kubo-Martin-Schwinger relation holds in the hard loop regime for any particle momentum distribution function that is reflection symmetric. This supports the equivalence, for 2-to-2 scattering processes, of the diagrammatic and kinetic approaches to calculating the photon emission rate. We compare the viscous rates from these two approaches at weak and realistic coupling strengths and provide parametrizations of the equilibrium and viscous photon emission rates for phenomenological studies in relativistic heavy-ion collisions.

I investigate the pairing properties at finite temperature of the Wigner–Seitz cells in the inner crust of a neutron star obtained with the recent Brussels–Montreal Skyrme functional BSk21. In particular I analyze the phenomena of persistence and reentrance of pairing correlations and their impact on the specific heat in the low-density region of the inner crust.

There is a degeneracy between the equation of state (EOS) of superdense neutron-rich nuclear matter and the strong-field gravity in understanding properties of neutron stars. While the EOS is still poorly known, there are also longstanding ambiguities in choosing Einstein's general relativity (GR) or alternative gravity theories in the not-so-well-tested strong-field regime. Besides the possible appearance of hyperons and new phases, the most uncertain part of the nucleonic EOS is currently the density dependence of nuclear symmetry energy especially at suprasaturation densities. At the same time, the EOS of symmetric nuclear matter (SNM) has been significantly constrained at saturation and suprasaturation densities. To provide information that may help break the EOS-gravity degeneracy, we investigate effects of nuclear symmetry energy within its uncertain range determined by recent terrestrial nuclear laboratory experiments on the gravitational binding energy and space-time curvature of neutron stars within GR and the scalar-tensor subset of alternative gravity models, constrained by recent measurements of the relativistic binary pulsars J1738 + 0333 and J0348 + 0432. In particular, we focus on effects of the following three parameters characterizing the EOS of superdense neutron-rich nucleonic matter: (1) the incompressibility $K_0$ of SNM, (2) the slope $L$ of nuclear symmetry energy at saturation density, and (3) the high-density behavior of nuclear symmetry energy. We find that the variation of either the density slope $L$ or the high-density behavior of nuclear symmetry energy leads to large changes in both the binding energy and the curvature of neutron stars while effects of varying the more constrained $K_0$ are negligibly small. The difference in predictions using the GR and the scalar-tensor theory appears only for massive neutron stars, and even then it is significantly smaller than the differences resulting from variations in the symmetry energy. We conclude that, within the scalar-tensor subset of gravity models, the EOS-gravity degeneracy has been broken by the recent relativistic pulsar measurements and that measurements of neutron-star properties sensitive to the compactness constrain mainly the density dependence of the symmetry energy at saturation and suprasaturation densities.

Background: ${}^{15}\mathrm{Be}$ is expected to have low-lying $3/2^{+}$ and $5/2^{+}$ states. A first search did not find the $3/2^{+}$ [A. Spyrou et al., Phys. Rev. C 84, 044309 (2011)]; however, a resonance in ${}^{15}\mathrm{Be}$ was populated in a second attempt and determined to be unbound with respect to ${}^{14}\mathrm{Be}$ by 1.8(1) MeV with a tentative spin-parity assignment of $5/2^{+}$ [J. Snyder et al., Phys. Rev. C 88, 031303(R) (2013)].

Purpose: Search for the predicted ${}^{15}\mathrm{Be}3/2^{+}$ state in the three-neutron decay channel.

Method: A two-proton removal reaction from a 55 MeV/u ${}^{17}\mathrm{C}$ beam was used to populate neutron-unbound states in ${}^{15}\mathrm{Be}$. The two-, three-, and four-body decay energies of the ${}^{12}\mathrm{Be}+$ neutron(s) detected in coincidence were reconstructed using invariant mass spectroscopy. Monte Carlo simulations were performed to extract the resonance and decay properties from the observed spectra.

Results: The low-energy regions of the decay energy spectra can be described with the first excited unbound state of ${}^{14}\mathrm{Be}$ ($E_x=1.54$ MeV, $E_r=0.28$ MeV). Including a state in ${}^{15}\mathrm{Be}$ that decays through the first excited ${}^{14}\mathrm{Be}$ state slightly improves the fit at higher energies though the cross section is small.

Conclusions: A ${}^{15}\mathrm{Be}$ component is not needed to describe the data. If the $3/2^{+}$ state in ${}^{15}\mathrm{Be}$ is populated, the decay by three-neutron emission through ${}^{14}\mathrm{Be}$ is weak, $\le 11\%$ up to 4 MeV. In the best fit, ${}^{15}\mathrm{Be}$ is unbound with respect to ${}^{12}\mathrm{Be}$ by 1.4 MeV (unbound with respect to ${}^{14}\mathrm{Be}$ by 2.66 MeV) with a strength of $7\%$.

The presence of paired or unpaired protons and neutrons in the open-shell radioactive α emitter affects the preformation probability of the α cluster inside it. The α-preformation probability inside the $\mathrm{odd}(Z\left)\text{−}\mathrm{even}\right(N)$, $\mathrm{even}(Z\left)\text{−}\mathrm{odd}\right(N)$, and $\mathrm{odd}(Z\left)\text{−}\mathrm{odd}\right(N)$ α emitters is investigated. The study is restricted to those decays with no angular momentum transfer to make a precise prediction about the mere pairing effect. The extended cluster model of α decay and the WKB approximation are used by taking into account the deformation degrees of freedom to carry out the calculations for 105 parent nuclei in the mass region of $A=175–289.$ The $\alpha$ + daughter interaction potential is calculated by using the Hamiltonian energy-density approach in terms of the SLy4 Skyrme-like interaction, then it is implemented to find the average decay width over the different orientations. The half-life of the decay is then estimated and employed in turn to extract the α-preformation probability by taking account of errors on both the released energy and the experimental half-life time. According to the present calculations, it is found that the α cluster preformation probability inside the nuclei which have unpaired nucleons is less than it would be in the neighboring nuclei of the same shell and subshell closures but have no unpaired nucleons. In particular, the effect of the single unpaired neutron in the $\mathrm{even}(Z\left)\text{−}\mathrm{odd}\right(N)$ nuclei is slightly larger than that of the single unpaired proton in the $\mathrm{odd}(Z\left)\text{−}\mathrm{even}\right(N)$ ones. The effect of the unpaired nucleons appears more clearly in the $\mathrm{odd}(Z\left)\text{−}\mathrm{odd}\right(N)$ nuclei which have both an unpaired neutron and an unpaired proton. Based on the obtained results, an empirical pairing term is added to the empirical formula [J. Phys. G 40, 105102 (2013)] that relates the α cluster preformation probability to the proton and neutron numbers outside the closed shells of the parent nucleus.

Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods.

Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT).

Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range.

Results: Two-dimensional PES's of ${}^{226,228,230,232}\mathrm{Th}$ and ${}^{232,234,236,238}\mathrm{U}$ are mapped and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and ${}^{238}\mathrm{U}$. The third minima in ${}^{230,232}\mathrm{Th}$ are very shallow, whereas those in ${}^{226,228}\mathrm{Th}$ and ${}^{238}\mathrm{U}$ are quite prominent. With the functional PC-PK1 a third barrier is found only in ${}^{226,228,230}\mathrm{Th}$. Single-nucleon levels around the Fermi surface are analyzed in ${}^{226}\mathrm{Th}$, and it is found that the formation of the third minimum is mainly due to the $Z=90$ proton energy gap at ${\beta }_{20}\approx 1.5$ and ${\beta }_{30}\approx 0.7$.

Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases with increasing neutron number. The origin of the third minimum is due to the proton $Z=90$ shell gap at relevant deformations.

The sub-barrier capture (fusion) reactions ${}^{32}\mathrm{S}+{}^{90,94,96}\mathrm{Zr}$, ${}^{36}\mathrm{S}+{}^{90,96}\mathrm{Zr}$, ${}^{40}\mathrm{Ca}+{}^{90,94,96}\mathrm{Zr}$, and ${}^{48}\mathrm{Ca}+{}^{90,96}\mathrm{Zr}$ with positive and negative $Q$ values for neutron transfer are studied with the quantum diffusion approach and the universal fusion function representation. For these systems, the $s$-wave capture probabilities are extracted from the experimental excitation functions and are also analyzed. Different effects of the positive $Q_{xn}$-value neutron transfer in the fusion enhancement are revealed in the relatively close reactions ${}^{32}\mathrm{S}+{}^{94,96}\mathrm{Zr}$ and ${}^{40}\mathrm{Ca}+{}^{94,96}\mathrm{Zr}$.

We report a measurement of $e^{+}{e}^{-}$ pairs from semileptonic heavy-flavor decays in $d+\text{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV. By exploring the mass and transverse-momentum dependence of the yield, the bottom decay contribution can be isolated from charm, and quantified by comparison to pythia and mc@nlo simulations. The resulting $b\overline{b}$-production cross section is ${\sigma }_{b\overline{b}}^{d\mathrm{Au}}=1.37\pm 0.28\left(\mathrm{stat}\right)\pm 0.46\left(\mathrm{syst}\right)$ mb, which is equivalent to a nucleon-nucleon cross section of ${\sigma }_{bb}^{NN}=3.4\pm 0.8\left(\mathrm{stat}\right)\pm 1.1\left(\mathrm{syst}\right)\mu b$.

We present a parametrization of the statistical rate function, $f$, for 20 superallowed $0^{+}\to 0^{+}$ nuclear $\beta$ transitions between $T=1$ analog states, and for 18 superallowed “mirror” transitions between analog $T=1/2$ states. All these transitions are of interest in the determination of $V_{ud}$. Although most of the transition $Q_{EC}$ values have been measured, their precision will undoubtedly be improved in the future. Our parametrization allows a user to easily calculate the corresponding new $f$ value to high precision $(\pm 0.01$%) without complicated computing.

A nucleon resonance with spin-parity $J^P=3/2^{-}$ and mass about 2.1 GeV is essential to reproducing the photoproduction cross sections for $\Lambda \left(1520\right)$ released by the LEPS and CLAS collaborations. It can be explained as the third nucleon resonance state ${[3/2^{-}]}_3$ in the constituent quark model so that there is no position to settle the $N\left(1875\right)$ which is listed by the Particle Data Group as the third $N3/2^{-}$ nucleon resonance. An interpretation is proposed that the $N\left(1875\right)$ is from the interaction of a decuplet baryon $\Sigma \left(1385\right)$ and an octet meson $K$, which is favored by the calculation of binding energy and decay pattern in a Bethe-Salpeter approach.

The Wigner $d$ function, which is the essential part of an irreducible representation of SU(2) and SO(3) parameterized with Euler angles, has been know to suffer from a serious numerical errors at high spins, if it is calculated by means of the Wigner formula as a polynomial of cos and sin of half of the second Euler angle. This paper shows a way to avoid this problem by expressing the $d$ functions as the Fourier series of the half angle. A precise numerical table of the coefficients of the series is provided as Supplemental Material.

We present a nucleon elastic scattering calculation based on Green's function formalism in the random-phase approximation. For the first time, the finite-range Gogny effective interaction is used consistently throughout the whole calculation to account for the complex, nonlocal, and energy-dependent optical potential. Effects of intermediate single-particle resonances are included and found to play a crucial role in the account for measured reaction cross sections. Double counting of the particle-hole second-order contribution is carefully addressed. The resulting integro-differential Schrödinger equation for the scattering process is solved without localization procedures. The method is applied to neutron and proton elastic scattering from ${}^{40}\mathrm{Ca}$. A successful account for differential and integral cross sections, including analyzing powers, is obtained for incident energies up to 30 MeV. Discrepancies at higher energies are related to a much-too-high volume integral of the real potential for large partial waves. This work opens the way to simultaneously assess effective interactions suitable for both nuclear structure and reactions.