In this work, we study the thermal evolution of twin star pairs, i.e., stars that present the same mass but different radius and compactness. We collect available equations of state that give origin to a second branch of stable compact stars with quarks in their core. For each equation of state, we investigate the particle composition inside stars and how differently each twin evolves over time, which depends on the central density/pressure and consequent crossing of the threshold for the Urca cooling process. We find that, although the general stellar thermal evolution depends on mass and particle composition, within one equation of state, only twin pairs that differ considerably on compactness can be clearly distinguished by how they cool down.

The properties of the deformed halo of ${}^{31}\mathrm{Ne}$ are discussed using the antisymmetrized molecular dynamics plus resonating group method $(\mathrm{AMD}+\mathrm{RGM})$. The $\mathrm{AMD}+\mathrm{RGM}$ calculations describe a large neutron radius for the ground state and reveal that the ground state is dominated by core-excited components. The resonant states are also investigated by applying the analytical continuation of the coupling constant. It is found that the first excited state (the $5/2^{-}$ state) is also dominated by core-excited components and has a small decay width, whereas the second excited state (the $7/2^{-}$ state) is dominated by the valence neutron in the $f$ wave coupled to the ground state of ${}^{30}\mathrm{Ne}$.

I revisit the construction of first-order spin hydrodynamics and find that the constitution relations receive the corrections from the cross effects resulting from spin-orbit coupling. Starting from a routine entropy analysis, I show how to identify cross effects and new cross transport coefficients from the second law of thermodynamics. Interestingly, the conventional transport coefficient heat conductivity $\kappa$ is bounded from below by the product of cross transport coefficients, which means the threshold of heat conduction is changed. With recourse to Zubarev's nonequilibrium statistical operator, we reproduce the construction of first-order spin hydrodynamics and identification of cross effects in a more rigorous way. By seeking the dispersion relations of normal modes, I find that these cross effects suppress the attenuation of sound modes and heat mode appearing in conventional hydrodynamics and also have impacts on the damping of non-hydrodynamic spin modes.

Assuming that quark and antiquark numbers are separately conserved during hadronization, I calculate bremsstrahlung photons from a hadronizing quark-gluon plasma. The quark and antiquark numbers are obtained from the hadron numbers in the statistical model and the transition amplitudes for the hadronization from the constraint that all quarks and antiquarks must be consumed in the hadronization. Then bremsstrahlung photons from the hadronization are obtained in the soft photon approximation, and one finds that their contribution to the direct photons increases in low-energy heavy-ion collisions and in peripheral collisions where the lifetime of a quark-gluon plasma (QGP) is relatively short.

Effective spectral functions of the $\rho$ meson are reconstructed by considering the lifetimes inside different media using the hadronic transport SMASH (Simulating Many Accelerated Strongly interacting Hadrons). Due to inelastic scatterings, resonance lifetimes are dynamically shortened (collisional broadening), even though the employed approach assumes vacuum resonance properties. Analyzing the $\rho$ meson lifetimes allows one to quantify an effective broadening of the decay width and spectral function, which is important in order to distinguish dynamical effects from additional genuine medium modifications to the spectral functions, indicating, e.g., an onset of chiral symmetry restoration. The broadening of the spectral function in a thermalized system is shown to be consistent with other theoretical calculations. The effective $\rho$ meson spectral function is also presented for the dynamical evolution of heavy-ion collisions, and shows a clear correlation of the broadening to system size, which is explained by an observed dependence of the width on the local hadron density. Furthermore, the difference in the results between the thermal system and full collision dynamics is explored, which may point to nonequilibrium effects.

In this paper, the parametrization of the nuclear structure function, which is directly constrained by the dynamics of QCD in its high-energy limit, is considered. This simple parametrization of the nuclear structure function is obtained from the proton experimental data by relying on a Froissart-bounded parametrization of the proton structure function. This phenomenological model describes high-energy QCD in the presence of saturation effects. Numerical calculations and comparison with available data from the NMC, EMC, and E665 Collaborations demonstrate that the suggested method by Armesto, Salgado, and Wiedemann (the ASW model) provides a reliable ratio of the nuclear structure functions $F_2^A/A{F}_2^p$ at low $x$ for light and heavy nuclei. The magnitude of nuclear shadowing is predicted for various kinematic regions and can be applied as well in the analysis of ultrahigh-energy processes by future experiments at electron-ion colliders.

This paper presents an extension of the MK single-pion production model [Kabirnezhad, Phys. Rev. D 97, 013002 (2018); Phys. Rev. D 102, 053009 (2020)] to high hadron invariant mass ($W$) and high momentum transfer ($Q^2$) to conform to the predictions of perturbative QCD due to the quark-hadron duality evidence. New form factors for several resonances and nonresonant background in the electron-nucleon cross sections are determined taking into account the experimental data and improved evaluation techniques. Fits to electron-proton scattering data are used to constrain free parameters and to assign the related uncertainties of the model. The results from this work can be used to determine the vector current in the corresponding neutrino-nucleon cross sections, which is an important input for event generators in long-baseline neutrino-oscillation measurements.

The $\mathrm{\Lambda }$ separation energies of the isospin triplet ${}_{\mathrm{\Lambda }}{}^7\mathrm{He}, {}_{\mathrm{\Lambda }}{}^7\mathrm{Li}^{*}, {}_{\mathrm{\Lambda }}{}^7\mathrm{Be}$, and the $T=1/2$ doublet ${}_{\mathrm{\Lambda }}{}^8\mathrm{Li}, {}_{\mathrm{\Lambda }}{}^8\mathrm{Be}$ are investigated within the no-core shell model. Calculations are performed based on a hyperon-nucleon potential derived from chiral effective field theory at next-to-leading order. The potential includes the leading charge-symmetry breaking (CSB) interaction in the $\mathrm{\Lambda }N$ channel, whose strength has been fixed to the experimentally known difference of the $\mathrm{\Lambda }$ separation energies of the mirror hypernuclei ${}_{\mathrm{\Lambda }}{}^4\mathrm{He}$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$. It turns out that the CSB predicted for the $A=7$ systems is small and agrees with the splittings deduced from the empirical binding energies within the experimental uncertainty. In the case of the $A=8$ doublet, the computed CSB is somewhat larger than the available experimental value.

The nuclear properties of ${}^{36}\mathrm{Ar}$ composite $\alpha$-like nuclei produced at 46.72 MeV of excitation energy via the ${}^{24}\mathrm{Mg}+{}^{12}\mathrm{C}$ reaction were investigated. In the past, at this excitation energy, resonant structures with peak-to-valley variation of 50–100 mb have been observed for this system and associated with fusion cross sections. To reveal the nature of this phenomenon the fusion channel observable was investigated. Exclusive measurements of $\alpha$ particles and evaporation residues were carried out at Laboratori Nazionali di Legnaro using the $8\pi \mathrm{LP}$ apparatus coupled to an evaporation residue detector. Then the experimental data were interpreted through the comparison with statistical model predictions. The energy spectra in coincidence with evaporation residues evidence the limitation of the statistical model assuming nuclear shape of the compound nucleus according to the rotating liquid drop model. To reproduce the experimental data very elongated nuclear shapes and reduced barriers for light particle emission have to be considered, with a major to minor axis ratio up to 3 at higher angular momenta. This large value for the axis ratio is selected in agreement with the predictions of the cranked cluster model and is consistent with previous findings for $\alpha$-like nuclei.

Background: The neutron scattering data was previously analyzed using a semi-microscopic optical model with channel coupling to inelastic excited states [Phys. Rev. C 100, 014603 (2019)]. The real part of the potential was constructed by single folding the density-independent M3Y-Paris bare nucleon-nucleon ($NN$) interaction, with zero-range knock-on exchange term, over the density of the target nucleus. The model reproduced the overall features of the inelastic angular distributions and polarization data. The elastic angular distributions were well reproduced.

Purpose: In this work we test the effectiveness of the semi-microscopic optical model with channel coupling, but we employ a density-dependent BDM3Y1-Paris bare ($NN$) interaction, with the finite-range form of the knock-on exchange term, in describing the scattering observables, particularly, the inelastic distributions and polarization data.

Method: The real volume term of the semi-microscopic model is constructed by single folding the density-dependent BDM3Y1-Paris bare ($NN$) interaction, over the matter distribution of the target nucleus. The ground state is coupled to low-lying inelastic excitation levels. The potential parameters are determined by fitting the elastic, inelastic, and polarization data corresponding to nucleon scattering off a wide range of mass numbers in the range $7\le A\le 208$ for various energies from 10–95 MeV.

Results: The density-dependent model resulted in significant improvements in the description of the inelastic angular distributions and analyzing power. In addition, the potential depths showed systematic linear dependence on incident energy, and one set of geometrical parameters is obtained for each nuclear target. We used our best-fit potential parameters to calculate the total cross sections corresponding to nucleon scattering off the considered nuclei. The calculated cross sections are in good agreement with the measured data.

Conclusions: In a semi-microscopic optical model, construction of the real volume term by single folding the density-dependent BDM3Y1-Paris bare ($NN$) interaction, with finite form of the knock-on exchange term, results in significant improvements in reproducing the inelastic angular distributions and polarization data as compared to the case of using the density-independent M3Y-Paris bare nucleon-nucleon ($NN$) interaction, with either zero-range or finite-range exchange term.

We build a relativistic model to perform calculations of exclusive, semiexclusive, and inclusive unpolarized cross sections and various polarization observables in electron and neutrino scattering experiments with deuteron targets. The strong interaction dynamics is defined by an explicit dynamical unitary representation of the Poincaré group, where representations of space translations and rotations in the interacting and noninteracting representations are the same. The Argonne V18 potential is used to construct a relativistic nucleon-nucleon interaction reproducing the experimental deuteron binding energy and nucleon-nucleon scattering observables. Our formalism does not include the pion production channel and neglects two-body contributions in the electromagnetic as well as in the weak nuclear current operator. We show that it is applicable to processes at kinematics, where the internal two-nucleon energy remains below the pion production threshold but the magnitude of the three-momentum transfer extends at least to several GeV.

The nucleus ${}^{11}\mathrm{C}$ plays an important role in the boron-proton fusion reactor environment as a catalyzer of the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ reaction which, by producing a long-lived isotope of ${}^7\mathrm{Be}$, poisons the aneutronic fusion process ${}^{11}\mathrm{B}(p,2\alpha ){}^4\mathrm{He}$. The low-energy cross section of ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ depends on the near-threshold states $7/2_1^{+}, 5/2_2^{+}, 5/2_3^{+}$ in ${}^{11}\mathrm{C}$ whose properties are primarily known from the indirect measurements. In this work, we present the theoretical analysis of these resonances and their collectivization via the coupling to the proton emission threshold. By using the shell model embedded in the continuum, we show that a significant collectivization takes place that enhances the spectroscopic factor of proton capture confirming the phenomenological value of Wiescher et al. [Phys. Rev. C 95, 044617 (2017)].

Background: Mainly because of its long half-life and despite its scientific relevance, spectroscopic measurements of ${}^{176}\mathrm{Lu}$ forbidden $\beta$ decays are very limited and lack formulation of shape factors. A direct precise measurement of its Q value is also presently unreported. In addition, the description of forbidden decays provides interesting challenges for nuclear theory. The comparison of precise experimental results with theoretical calculations for these decays can help to test underlying models and can aid the interpretation of data from other experiments.

Purpose: Perform the first precision measurements of ${}^{176}\mathrm{Lu}\beta$-decay spectra and attempt the observation of its electron capture decays, as well as perform the first precision direct measurement of the ${}^{176}\mathrm{Lu}\beta$-decay Q value. Compare the shape of the precisely determined experimental $\beta$ spectra to theoretical calculations, and compare the end point energy to that obtained from an independent Q value measurement.

Method: The ${}^{176}\mathrm{Lu}\beta$-decay spectra measurements and the search for electron capture decays were performed with an experimental setup that employed lutetium-containing scintillator crystals and a NaI(Tl) spectrometer for coincidence counting. The $\beta$ decay Q value was determined via high-precision Penning trap mass spectrometry (PTMS) with the LEBIT facility at the National Superconducting Cyclotron Laboratory. The $\beta$-spectrum calculations were performed within the Fermi theory formalism with nuclear structure effects calculated using a shell model approach.

Results: Both $\beta$ transitions of ${}^{176}\mathrm{Lu}$ were experimentally observed and corresponding shape factors formulated in their entire energy ranges. The search for electron capture decay branches led to an experimental upper limit of $6.3\times {10}^{-6}$ relative to its $\beta$ decays. The ${}^{176}\mathrm{Lu}\beta$-decay and electron capture Q values were measured using PTMS to be 1193.0(6) and 108.9(8) keV, respectively. This enabled precise $\beta$ end point energies of 596.2(6) and 195.3(6) keV to be determined for the primary and secondary $\beta$ decays, respectively. The conserved vector current hypothesis was applied to calculate the relativistic vector matrix elements. The $\beta$-spectrum shape was shown to significantly depend on the Coulomb displacement energy and on the value of the axial vector coupling constant $g_A$, which was extracted according to different assumptions.

Conclusion: The implemented self-scintillation method has provided unmatched observations of ${}^{176}\mathrm{Lu}$, independently validated by the first direct measurements of its $\beta$-decay Q value by Penning trap mass spectrometry. Theoretical study of the main $\beta$ transition led to the extraction of very different effective $g_A$ and ${log}_{10}f$ values, showing that a high-precision description of this transition would require a realistic nuclear structure with nucleus deformation.

The time evolution of particle number fluctuations in nuclear collisions at intermediate energies ($E_{\mathrm{lab}}=1.23\text{–}10A\mathrm{GeV}$) is studied by means of the UrQMD-3.5 transport model. The transport description incorporates baryonic interactions through a density-dependent potential. This allows for an implementation of a first-order phase transition including a mechanically unstable region at large baryon density. The scaled variance of the baryon and proton number distributions is calculated in the central cubic spatial volume of the collisions at different times. A significant enhancement of fluctuations associated with the unstable region is observed. This enhancement persists to late times, reflecting a memory effect for the fluctuations. The presence of the phase transition has a much smaller influence on the observable event-by-event fluctuations of protons in momentum space.

The ring structures that appear in $\mathrm{Au}+\mathrm{Au}$ collisions at collision energies $\sqrt{s_{NN}}=$ 3–30 GeV are studied. The calculations are performed within the model of three-fluid dynamics. It is demonstrated that a pair of vortex rings are formed, one at forward and another at backward rapidities, in ultracentral $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}>$ 4 GeV. The vortex rings carry information about the early stage of the collision, in particular about the stopping of baryons. It is shown that these rings can be detected by measuring the ring observable $R_{\mathrm{\Lambda }}$ even in the rapidity range $0<y<0.5$ (or $-0.5<y<0$) on the level of 0.5–1.5% at $\sqrt{s_{NN}}=$ 5–20 GeV. At forward/backward rapidities, the $R_{\mathrm{\Lambda }}$ signal is expected to be stronger. The possibility of observation of the vortex-ring signal against the background of noncollective transverse polarization is discussed.

The excitation scheme of the ${}^{63}\mathrm{Cu}$ nucleus has been probed following its population in a light-ion induced fusion-evaporation reaction and using an array of Compton suppressed HPGe clover detectors as the detection system. Apart from ascribing $\gamma$-ray transitions to the level scheme of the nucleus, through $\gamma \text{−}\gamma$ coincidence measurements, and identifying the new transitions in the process, measurements of angular correlation and linear polarization of the $\gamma$ rays have also been carried out towards assigning their multipolarities and electric and magnetic characters. The observed level scheme has been interpreted through shell model calculations in two different model spaces. One of these was the $f5pg9$ space outside the ${}^{56}\mathrm{Ni}$ core while the other included the $f_{7/2}$ orbital for the protons outside the ${}^{48}\mathrm{Ca}$ core and was directed at probing the influence of the $f_{7/2}$ excitations in the regime of spins being investigated. The latter has been found to be of rather modest impact, in general, and the observed level structure can largely be interpreted through particle excitations in the $f5pg9$ model space.

The α decay and $2\alpha$ decay of various isotopes of Pu, Am, Cm, Bk, Cf, Es, Fm, and Md in the mass region $A=218$ to 273 are investigated using the modified generalized liquid drop model (MGLDM) and universal decay law. The comparison of experimental alpha decay half-lives with the predicted half-lives proves the consistency of our calculations. As a result we broadened our investigation to also include a study of double alpha decay of these isotopes. There is a considerable interest in performing research on double alpha decay, as seen by the proposal submitted at CERN to investigate the double alpha radioactivity of ${}^{224}\mathrm{Ra}$. In view of this, the decay half-lives of most probable $2\alpha$ emitters, calculated using MGLDM by employing different preformation factors, are presented which can be beneficial for upcoming experimental investigations on this topic. A peak or dip in α and $2\alpha$ decay half-life is witnessed which indicates the stability of parent or daughter isotopes correspondingly. Minimum and maximum half-lives for decay are observed when the daughter and parent nuclei, respectively, contain a magic number of neutrons. From our study, 126 and 162 are found as magic/semimagic numbers. A linear plot is obtained while plotting ${\log }_{10}{T}_{1/2}$ of all the isotopes against $Z{Q}^{-1/2}$, which emphasizes that our estimations are reliable.

Azimuthal anisotropy of produced particles is one of the most important observables used to access the collective properties of the expanding medium created in relativistic heavy-ion collisions. In this paper, we present second ($v_2$) and third ($v_3$) order azimuthal anisotropies of $K_S^0, \varphi , \mathrm{\Lambda }, \mathrm{\Xi }$, and $\mathrm{\Omega }$ at midrapidity ($\left|y\right|<1$) in Au+Au collisions at $\sqrt{s_{NN}}=54.4$ GeV measured by the STAR detector. The $v_2$ and $v_3$ are measured as a function of transverse momentum and centrality. Their energy dependence is also studied. $v_3$ is found to be more sensitive to the change in the center-of-mass energy than $v_2$. Scaling by constituent quark number is found to hold for $v_2$ within 10%. This observation could be evidence for the development of partonic collectivity in 54.4 GeV Au+Au collisions. Differences in $v_2$ and $v_3$ between baryons and antibaryons are presented, and ratios of $v_3/v_2^{3/2}$ are studied and motivated by hydrodynamical calculations. The ratio of $v_2$ of $\varphi$ mesons to that of antiprotons $[v_2\left(\varphi \right)/v_2\left(\overline{p}\right)]$ shows centrality dependence at low transverse momentum, presumably resulting from the larger effects from hadronic interactions on antiproton $v_2$.

Nucleosynthesis in primordial stellar environments may lead to a substantial production of ${}^{10}\mathrm{B}$ isotopes, which either are converted by the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ reaction to ${}^7\mathrm{Be}$ or processed further by ${}^{10}\mathrm{B}+\alpha$ reactions towards the carbon, nitrogen, and oxygen range. This paper focuses on low energy studies of the ${}^{10}\mathrm{B}(\alpha ,p){}^{13}\mathrm{C}$ and ${}^{10}\mathrm{B}(\alpha ,d){}^{12}\mathrm{C}$ reactions to determine the low energy cross section and the reaction rates in stellar environments using $R$-matrix analysis techniques. The experimental results cover a broad energy range, from 0.21 MeV up to 1.4 MeV in the center of mass frame, extending down to the Gamow energy range. A substantial increase in the reaction rate compared to previous predictions is found, due to the identification of near threshold $\alpha$-cluster resonance structures.