The quasielastic scattering of muon neutrino and electrons on a carbon target are analyzed using the relativistic distorted-wave impulse approximation (RDWIA). We also evaluate the contribution of the two-particle and two-hole meson exchange current ($2p\text{−}2h$ MEC) to electroweak response functions. The nuclear model dependence of the (anti)neutrino cross sections is studied within the RDWIA+MEC approach and RDWIA model with the large nucleon axial mass. It is shown that the results for the squared momentum transfer distribution $d\sigma /d{Q}^2$ and for invariant mass of the final hadronic system distribution $d\sigma /dW$ obtained within these models are substantially different.

We present a minimal nuclear energy density functional (NEDF) called “SeaLL1” that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by seven significant phenomenological parameters, each related to a specific nuclear property. It describes the nuclear masses of even-even nuclei with a mean energy error of $0.97\mathrm{MeV}$ and a standard deviation of $1.46\mathrm{MeV}$, two-neutron and two-proton separation energies with rms errors of $0.69\mathrm{MeV}$ and $0.59\mathrm{MeV}$ respectively, and the charge radii of 345 even-even nuclei with a mean error ${\epsilon }_r=0.022\mathrm{fm}$ and a standard deviation ${\sigma }_r=0.025\mathrm{fm}$. SeaLL1 incorporates constraints on the equation of state (EoS) of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body ($\mathit{NN}$) interactions at the next-to-next-to-next-to leading order (N3LO) level and three-body ($\mathit{NNN}$) interactions at the next-to-next-to leading order (N2LO) level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. We identify additional phenomenological parameters that have little effect on ground-state properties but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.

I have examined spectroscopic factors for predominantly $1d_{5/2}$ single-particle states in isospin multiplets having $A=14-16$. Results indicate a serious problem with the width of the $5/2^{+}$ resonance in ${}^{15}\mathrm{F}$. Calculations provide recommended widths in ${}^{14}\mathrm{O}$ and ${}^{16}\mathrm{F}$.

The reaction ${}^{12}\mathrm{C}+{}^{13}\mathrm{C}$ at $95\mathrm{MeV}$ bombarding energy is studied using the Garfield + Ring Counter apparatus located at the INFN Laboratori Nazionali di Legnaro. In this paper we want to investigate the de-excitation of ${}^{25}\mathrm{Mg}$ aiming both at a new stringent test of the statistical description of nuclear decay and a direct comparison with the decay of the system ${}^{24}\mathrm{Mg}$ formed through ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reactions previously studied. Thanks to the large acceptance of the detector and to its good fragment identification capabilities, we could apply stringent selections on fusion-evaporation events, requiring their completeness in charge. The main decay features of the evaporation residues and of the emitted light particles are overall well described by a pure statistical model; however, as for the case of the previously studied ${}^{24}\mathrm{Mg}$, we observed some deviations in the branching ratios, in particular for those chains involving only the evaporation of $\alpha$ particles. From this point of view the behavior of the ${}^{24}\mathrm{Mg}$ and ${}^{25}\mathrm{Mg}$ decay cases appear to be rather similar. An attempt to obtain a full mass balance even without neutron detection is also discussed.

Evidence of the enhanced nuclear radius in the Hoyle rotational state, $2_2^{+}$, is derived from the differential cross sections in $\alpha +{}^{12}\mathrm{C}$ inelastic scattering. The prominent shrinkage is observed in the differential cross section of the $2_2^{+}$ state in comparison to the yrast $2_1^{+}$ state, and this shrinkage is the first evidence of the enhanced nuclear radius which originates from the $3\alpha$ structure in the $2_2^{+}$ state. A diffraction formula, that is, Blair's phase rule, is applied to the differential cross sections, and the present analysis predicts an enhancement of 0.6 to 1.0 fm in the nuclear radius of the $2_2^{+}$ state in comparison to the radius of the yrast $2_1^{+}$, which is considered to have a normal nuclear radius. Constraint on the recent ab initio calculation for $3\alpha$ states in ${}^{12}\mathrm{C}$ is also discussed.

In this work, we improve on and extend to low- and high-$Q^2$ values the extractions of the two-photon-exchange (TPE) amplitudes and the ratio $P_l/P_l^{\mathrm{Born}}(\varepsilon ,Q^2)$ using world data on electron-proton elastic scattering cross section ${\sigma }_R(\varepsilon ,Q^2)$ with an emphasis on data covering the high-momentum region, up to $Q^2=5.20{(\mathrm{GeV}/\mathrm{c})}^2$, to better constrain the TPE amplitudes in this region. We provide a new parametrization of the TPE amplitudes, along with an estimate of the fit uncertainties. We compare the results to several previous phenomenological extractions and hadronic TPE predictions. We use the new parametrization of the TPE amplitudes to extract the ratio $P_l/P_l^{\mathrm{Born}}(\varepsilon ,Q^2)$, and then compare the results to previous extractions, several theoretical calculations, and direct measurements at $Q^2=2.50{(\mathrm{GeV}/\mathrm{c})}^2$.

Background: The evolution of nuclear magic numbers at extremes of isospin is a topic at the forefront of contemporary nuclear physics. $N=50$ is a prime example, with increasing experimental data coming to light on potentially doubly magic ${}^{100}\mathrm{Sn}$ and ${}^{78}\mathrm{Ni}$ at the proton-rich and proton-deficient extremes, respectively; however, experimental discrepancies exist in the data for less exotic systems.

Purpose: In ${}^{86}\mathrm{Kr}$ the $B(E2;2_1^{+}\to 0_1^{+})$ value—a key indicator of shell evolution—has been experimentally determined by two different methodologies, with the results deviating by $3\sigma$. Here, we report on a new high-precision measurement of this value, as well as the first measured lifetimes and hence transition strengths for the $2_2^{+}$ and $3_{\left(2\right)}^{-}$ states in the nucleus.

Methods: The Doppler-shift attenuation method was implemented using the TRIUMF-ISAC $\gamma$-ray escape-suppressed spectrometer (TIGRESS) $\gamma$-ray spectrometer and the TIGRESS integrated plunger device. High-statistics Monte Carlo simulations were utilized to extract lifetimes in accordance with state-of-the-art methodologies.

Results: Lifetimes of $\tau \left(2_1^{+}\right)=336\pm 4\text{(stat.)}\pm 20\text{(sys.)}$ fs, $\tau \left(2_2^{+}\right)=263\pm 9\text{(stat.)}\pm 19\text{(sys.)}$ fs, and $\tau \left(3_{\left(2\right)}^{-}\right)=73\pm 6\text{(stat.)}\pm 32\text{(sys.)}$ fs were extracted. This yields a transition strength for the first-excited state of $B(E2;2_1^{+}\to 0_1^{+})=259\pm 3\text{(stat.)}\pm 16\text{(sys.)}$ $e^2$ ${\mathrm{fm}}^4$.

Conclusions: The measured lifetime disagrees with the previous Doppler-shift attenuation method measurement by more than $3\sigma$, while agreeing well with a previous value extracted from Coulomb excitation. The newly extracted $B(E2;2_1^{+}\to 0_1^{+})$ value indicates a more significant reduction in the $N=50$ isotones approaching $Z=40$.

Excited states in the neutron-rich isotopes ${}^{33}\mathrm{P}$ and ${}^{34}\mathrm{P}$ were populated by the ${}^{18}\mathrm{O}+{}^{18}\mathrm{O}$ fusion-evaporation reaction at $E_{\mathrm{lab}}=24$ MeV. The Gammasphere array was used along with the Microball particle detector array to detect $\gamma$ transitions in coincidence with the charged particles emitted from the compound nucleus ${}^{36}\mathrm{S}$. The use of Microball enabled the selection of the proton emission channel. It also helped in determining the exact position and energy of the emitted proton; this was later employed in kinematic Doppler corrections. 16 new transitions and 13 new states were observed in ${}^{33}\mathrm{P}$ and 21 $\gamma$ rays and 20 energy levels were observed in ${}^{34}\mathrm{P}$ for the first time. The nearly $4\pi$ geometry of Gammasphere allowed the measurement of $\gamma$-ray angular distributions leading to spin assignments for many states. The experimental observations for both isotopes were interpreted with the help of shell-model calculations using the (0+1)$\hslash \omega$ PSDPF interaction. The calculations accounted for both the 0p-0h and 1p-1h states reasonably well and indicated that 2p-2h excitations might dominate the higher-spin configurations in both ${}^{33}\mathrm{P}$ and ${}^{34}\mathrm{P}$.

The validity of impact parameter estimation from the multiplicity of charged particles at low-intermediate energies is checked within the framework of the improved quantum molecular dynamics model. The simulations show that the multiplicity of charged particles cannot estimate the impact parameter of heavy ion collisions very well, especially for central collisions at the beam energies lower than $\sim 70$ MeV/u due to the large fluctuations of the multiplicity of charged particles. The simulation results for the central collisions defined by the charged particle multiplicity are compared to those by using impact parameter $b=2$ fm and it shows that the charge distribution for ${}^{112}\mathrm{Sn}+{}^{112}\mathrm{Sn}$ at the beam energy of 50 MeV/u is different evidently for two cases; and the chosen isospin sensitive observable, the coalescence invariant single neutron to proton yield ratio, reduces less than 15% for neutron-rich systems ${}^{124,132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at $E_{\mathrm{beam}}=50$ MeV/u, while the coalescence invariant double neutron to proton yield ratio does not have obvious difference. The sensitivity of the chosen isospin sensitive observables to effective mass splitting is studied for central collisions defined by the multiplicity of charged particles. Our results show that the sensitivity is enhanced for ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ relative to that for ${}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$, and this reaction system should be measured in future experiments to study the effective mass splitting by heavy ion collisions.

The dynamics of baryon-antibaryon annihilation and reproduction ($B\overline{B}\leftrightarrow 3M$) is studied within the Parton-Hadron-String Dynamics (PHSD) transport approach for Pb+Pb and Au+Au collisions as a function of centrality from lower Super Proton Synchrotron (SPS) up to Large Hadron Collider (LHC) energies on the basis of the quark rearrangement model. At Relativistic Heavy-Ion Collider (RHIC) energies we find a small net reduction of baryon-antibaryon ($B\overline{B}$) pairs while for the LHC energy of $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ a small net enhancement is found relative to calculations without annihilation (and reproduction) channels. Accordingly, the sizable difference between data and statistical calculations in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV for proton and antiproton yields [ALICE Collaboration, B. Abelev et al., Phys. Rev. C 88, 044910 (2013)], where a deviation of 2.7 $\sigma$ was claimed by the ALICE Collaboration, should not be attributed to a net antiproton annihilation. This is in line with the observation that no substantial deviation between the data and statistical hadronization model (SHM) calculations is seen for antihyperons, since according to the PHSD analysis the antihyperons should be modified by the same amount as antiprotons. As the PHSD results for particle ratios are in line with the ALICE data (within error bars) this might point towards a deviation from statistical equilibrium in the hadronization (at least for protons and antiprotons). Furthermore, we find that the $B\overline{B}\leftrightarrow 3M$ reactions are more effective at lower SPS energies where a net suppression for antiprotons and antihyperons up to a factor of 2–2.5 can be extracted from the PHSD calculations for central Au+Au collisions.

The phase transition from hadronic matter to chirally symmetric quark-gluon plasma is expected to be a rapid crossover at zero quark chemical potential ($\mu$), becoming first order at some finite value of $\mu$, indicating the presence of a critical point. Using a three-flavor soft-wall model of anti–de Sitter/QCD, we investigate the effect of varying the light and strange quark masses on the order of the chiral phase transition. At zero quark chemical potential, we reproduce the Columbia Plot, which summarizes the results of lattice QCD and other holographic models. We then extend this holographic model to examine the effects of finite quark chemical potential. We find that the the chemical potential does not affect the critical line that separates first-order from rapid crossover transitions. This excludes the possibility of a critical point in this model, suggesting that a different setup is necessary to reproduce all the features of the QCD phase diagram.

We study the effect of an anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions. We use the Glauber model to generate initial conditions and ignore hydrodynamic expansion in the transverse direction. We employ the Beer-Lambert law to allow for the transmittance of produced hadrons in the medium and calculate the anisotropy generated due to the suppression of particles traversing through the medium. To separate non-flow contribution due to surface bias effects, we ignore hydrodynamic expansion in the transverse direction and consider purely longitudinal boost-invariant expansion. We calculate the transverse momentum dependence of elliptic flow, generated from an anisotropic escape mechanism due to surface bias effects, for various centralities in $\sqrt{s_{NN}}=200$ GeV $\mathrm{Au}+\mathrm{Au}$ collisions at the Relativistic Heavy Ion Collider and $\sqrt{s_{NN}}=2.76$ TeV $\mathrm{Pb}+\mathrm{Pb}$ collisions at the Large Hadron Collider. We find that the surface bias effects make a sizable contribution to the total elliptic flow observed in heavy-ion collisions, indicating that the viscosity of the QCD matter extracted from hydrodynamic simulations may be underestimated.

We investigate the robustness of third family solutions for hybrid compact stars with a quark matter core that correspond to the occurrence of high-mass twin stars against a softening of the phase transition by means of a construction that mimics the effects of pasta structures in the mixed phase. We consider a class of hybrid equations of state that exploits a relativistic mean-field model for the hadronic as well as for the quark matter phase. We present parametrizations that correspond to branches of high-mass twin star pairs with maximum masses between $2.05M_{\odot }$ and $1.48M_{\odot }$ having radius differences between 3.2 and 1.5 km, respectively. When compared to a Maxwell construction with a fixed value of critical pressure $P_c$, the effect of the mixed phase construction consists in the occurrence of a region of pressures around $P_c$ belonging to the coexistence of hadronic and quark matter phases between the onset pressure at $P_H$ and the end of the transition at $P_Q$. The maximum broadening which would still allow mass-twin compact stars is found to be ${(P_Q-P_H)}_{\max }\approx P_c$ for all parametrizations within the present class of models. At least the heavier of the neutron stars of the binary merger GW170817 could have been a member of the third family of hybrid stars. We present the example of another class of hybrid star equations of state for which the appearance of the third family branch is not as robust against mixed phase effects as that of the present work.

Background: The reaction rates used in $\gamma$-process nucleosynthesis network calculations are mostly derived from theoretical, statistical model cross sections. Experimental data is scarce for charged particle reactions at astrophysical, low energies. Where experimental ($\alpha ,\gamma$) data exists, it is often strongly overestimated by Hauser-Feshbach statistical model calculations. Further experimental $\alpha$-capture cross sections in the intermediate and heavy mass region are necessary to test theoretical models and to gain understanding of heavy element nucleosynthesis in the astrophysical $\gamma$ process.

Purpose: The aim of the present work is to measure the ${}^{121}\mathrm{Sb}(\alpha ,\gamma ){}^{125}\mathrm{I}, {}^{121}\mathrm{Sb}(\alpha ,\mathrm{n}){}^{124}\mathrm{I}$, and ${}^{123}\mathrm{Sb}(\alpha ,\mathrm{n}){}^{126}\mathrm{I}$ reaction cross sections. These measurements are important tests of astrophysical reaction rate predictions and extend the experimental database required for an improved understanding of p-isotope production.

Method: The $\alpha$-induced reactions on natural and enriched antimony targets were investigated using the activation technique. The ($\alpha ,\gamma$) cross sections of ${}^{121}\mathrm{Sb}$ were measured and are reported for the first time. To determine the cross section of the ${}^{121}\mathrm{Sb}(\alpha ,\gamma ){}^{125}\mathrm{I}, {}^{121}\mathrm{Sb}(\alpha ,\mathrm{n}){}^{124}\mathrm{I}$, and ${}^{123}\mathrm{Sb}(\alpha ,\mathrm{n}){}^{126}\mathrm{I}$ reactions, the yields of $\gamma$ rays following the $\beta$ decay of the reaction products were measured. For the measurement of the lowest cross sections, the characteristic x rays were counted with a low-energy photon spectrometer detector.

Results: The cross section of the ${}^{121}\mathrm{Sb}(\alpha ,\gamma ){}^{125}\mathrm{I}, {}^{121}\mathrm{Sb}(\alpha ,\mathrm{n}){}^{124}\mathrm{I}$, and ${}^{123}\mathrm{Sb}(\alpha ,\mathrm{n}){}^{126}\mathrm{I}$ reactions were measured with high precision in an energy range between 9.74 and 15.48 MeV, close to the astrophysically relevant energy window. The results are compared with the predictions of statistical model calculations. The ($\alpha$,n) data show that the $\alpha$ widths are predicted well for these reactions. The ($\alpha ,\gamma$) results are overestimated by the calculations but this is because of the applied neutron and $\gamma$ widths.

Conclusions: Relevant for the astrophysical reaction rate is the $\alpha$ width used in the calculations. While for other reactions the $\alpha$ widths seem to have been overestimated and their energy dependence was not described well in the measured energy range, this is not the case for the reactions studied here. The result is consistent with the proposal that additional reaction channels, such as Coulomb excitation, may have led to the discrepancies found in other reactions.

The abundance of large clusters of nucleons in neutron-rich matter at subnuclear density is found to be greatly reduced by finite-temperature effects when matter is close to $\beta$ equilibrium, compared to the case where the electron fraction is fixed at $Y_e>0.1$, as often considered in the literature. Large nuclei and exotic nonspherical nuclear configurations called pasta, favored in the vicinity of the transition to uniform matter at $T=0$, dissolve at a relatively low temperature $T_{\mathrm{u}}$ as protons leak out of nuclei and pasta. For matter at $\beta$ equilibrium with a negligible neutrino chemical potential we find that $T_{\mathrm{u}}^{\beta }\simeq 4\pm 1$ MeV for realistic equations of state. This is lower than the maximum temperature $T_{\max }^{\beta }\simeq 9\pm 1$ MeV at which nuclei can coexist with a gas of nucleons and can be explained by a change in the nature of the transition to uniform matter called retrograde condensation. An important new finding is that coherent neutrino scattering from nuclei and pasta makes a modest contribution to the opacity under the conditions encountered in supernovas and neutron star mergers. This is because large nuclear clusters dissolve at most relevant temperatures, and at lower temperatures, when clusters are present, Coulomb correlations between them suppress coherent neutrino scattering off individual clusters. Implications for neutrino signals from galactic supernovas are briefly discussed.

In-medium modifications of light cluster properties in warm stellar matter are studied within the relativistic mean-field approximation. In-medium effects are included by introducing an explicit binding energy shift analytically calculated in the Thomas-Fermi approximation, supplemented with a phenomenological modification of the cluster couplings to the $\sigma$ meson. A linear dependence on the $\sigma$ meson is assumed for the cluster mass, and the associated coupling constant is fixed by imposing that the virial limit at low density is recovered. The resulting cluster abundances come out to be in reasonable agreement with constraints at higher density coming from heavy-ion collision data. Some comparisons with microscopic calculations are also shown.

The Alt-Grassberger-Sandhas $N$-body theory is used to study interaction of $\eta$ mesons with $d, {}^3\mathrm{He}$, and ${}^4\mathrm{He}$. Separable expansion of the subamplitudes is adopted to convert the integral equations into the quasi-two-body form. The resulting formalism is applied to fit the existing data for low-energy $\eta$ production of few-nucleon targets. On the basis of this fitting procedure the scattering lengths $a_{\eta d}, a_{\eta {}^3\mathrm{He}}, a_{\eta {}^4\mathrm{He}}$ as well as the subthreshold behavior of the elementary $\eta N$ scattering amplitude are obtained.

We determine the probability distributions of the shear viscosity over the entropy density ratio $\eta /s$ in the quark-gluon plasma formed in Au + Au collisions at $\sqrt{s_{NN}}=19.6,39$, and $62.4\mathrm{GeV}$, using Bayesian inference and Gaussian process emulators for a model-to-data statistical analysis that probes the full input parameter space of a transport + viscous hydrodynamics hybrid model. We find the most likely value of $\eta /s$ to be larger at smaller $\sqrt{s_{NN}}$, although the uncertainties still allow for a constant value between 0.10 and 0.15 for the investigated collision energy range.