The first measurements of dielectron production at midrapidity $(\left|{\eta }_{\mathrm{e}}\right|<0.8)$ in proton–proton and proton–lead collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ at the LHC are presented. The dielectron cross section is measured with the ALICE detector as a function of the invariant mass $m_{\mathrm{ee}}$ and the pair transverse momentum $p_{\mathrm{T},\mathrm{ee}}$ in the ranges $m_{\mathrm{ee}}<3.5$ $\mathrm{GeV}/c^2$ and $p_{\mathrm{T},\mathrm{ee}}<8$ $\mathrm{GeV}/c$, in both collision systems. In proton–proton collisions, the charm and beauty cross sections are determined at midrapidity from a fit to the data with two different event generators. This complements the existing dielectron measurements performed at $\sqrt{s}=7$ and 13 TeV. The slope of the $\sqrt{s}$ dependence of the three measurements is described by FONLL calculations. The dielectron cross section measured in proton–lead collisions is in agreement, within the current precision, with the expected dielectron production without any nuclear matter effects for ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ pairs from open heavy-flavor hadron decays. For the first time at LHC energies, the dielectron production in proton–lead and proton–proton collisions are directly compared at the same $\sqrt{s_{\mathrm{NN}}}$ via the dielectron nuclear modification factor $R_{\mathrm{pPb}}$. The measurements are compared to model calculations including cold nuclear matter effects, or additional sources of dielectrons from thermal radiation.

We develop a study of the low energy kaon-$\mathrm{\Xi }$ interaction taking into account nonlinear chiral invariant Lagragians. We extend a model proposed to describe the $\pi N$ interaction to the $K\mathrm{\Xi }$ and $\overline{K}\mathrm{\Xi }$ interactions, considering $\mathrm{\Lambda }, \mathrm{\Sigma }$, and $\mathrm{\Omega }$ hyperons and the $\mathrm{\Omega }\left(2012\right)$ resonance in the intermediate states. We calculate their total cross sections, phase shifts, angular distributions, and polarizations in the center-of-mass frame of reference, accordingly to the proposed formalism.

At least three length scales are important in gaining a complete understanding of the physics of nuclei. These are the radius of the nucleus, the average inter-nucleon separation distance, and the size of the nucleon. The connections between the different scales are examined by using examples that demonstrate the direct connection between short-distance and high-momentum transfer physics and also that significant high-momentum content of wave functions is inevitable. The nuclear size is connected via the independent-pair approximation to the nucleon-nucleon separation distance, and this distance is connected via the concept of virtuality to the EMC effect. An explanation of the latter is presented in terms of light-front holographic wave functions of QCD. The net result is that the three scales are closely related, so that a narrow focus on any given specific range of scales may prevent an understanding of the fundamental origins of nuclear properties. It is also determined that, under certain suitable conditions, experiments are able to measure the momentum dependence of wave functions.

The present article investigates the role of heavy nuclear clusters and weakly bound light nuclear clusters based on a newly developed equation of state for core collapse supernova studies. A novel approach is brought forward for the description of nuclear clusters, taking into account the quasiparticle approach and continuum correlations. It demonstrates that the commonly employed nuclear statistical equilibrium approach, based on noninteracting particles, for the description of light and heavy clusters becomes invalid for warm nuclear matter near the saturation density. This has important consequences for studies of core collapse supernovae. To this end, we implement this nuclear equation of state provided for arbitrary temperature, baryon density, and isospin asymmetry, to spherically symmetric core collapse supernova simulations to study the impact on the dynamics as well as on the neutrino emission. For the inclusion of a set of weak processes involving light clusters the rate expressions are derived, including medium modifications at the mean-field level. A substantial impact from the inclusion of a variety of weak reactions involving light clusters on the post bounce dynamics and on the neutrino emission could not be found.

Background: Recent observation of mass-asymmetric fission in neutron-deficient Hg and Pt nuclei has reignited interest in fission fragment mass distributions close to Pb. Investigations at energies close to the fission barrier, where mass-asymmetric fission is expected to be most obvious and the sensitivity to shell effects is maximized, are limited in this mass region.

Purpose: To measure fission mass distributions for ${}^{205,207,209}\mathrm{Bi}$ nuclei at the lowest possible excitation energies to determine how the mass distributions change with excitation energy and the neutron number of the compound nucleus.

Method: Proton beams bombarding targets of ${}^{204,206,208}\mathrm{Pb}$ were used to study the fission of ${}^{205,207,209}\mathrm{Bi}$ at energies from just above to 10 MeV above their fission barriers. Fission fragments were measured using the CUBE fission spectrometer. Fission fragment mass distributions were determined using a newly developed time difference analysis method. Mass distributions were characterized by triple-Gaussian fits to determine the systematic trends across each isotope with excitation energy.

Results: Measured mass distributions of all three Bi isotopes exhibit a component of mass-asymmetric fission at all energies studied. The probability of mass-asymmetric fission decreases significantly with increasing excitation energy, from $\approx 70$ to $\approx 40\%$ over a 10-MeV range. Comparisons between the three Bi isotopes hint at an increase in the mass-symmetric fission yield with increasing neutron number, which could be due to a decrease in the difference between the symmetric and asymmetric fission barriers. The centroids of the mass-asymmetric peaks suggest that several deformed shell gaps in the fission fragments could be contributing to the presence of the mass-asymmetric fission mode with $Z_{\mathrm{light}}\simeq 38$, $Z_{\mathrm{heavy}}\simeq 45$, and $N_{\mathrm{light}}\simeq 56$ all present in the fission fragments.

Conclusions: Measurements of fission mass distributions at the lowest possible excitation energies above the fission barrier provide an excellent platform to investigate the origins of the mass-asymmetric fission mode. Further systematic measurements at these energies offer an opportunity to rigorously test new models of fission in this mass region.

The $\gamma$ process is an explosive astrophysical scenario, which is thought to be the primary source of the rare proton-rich stable $p$ nuclei. However, current $\gamma$-process models remain insufficient in describing the observed $p$-nuclei abundances, with disagreements up to two orders of magnitude. A sensitivity study has identified ${}^{111}\mathrm{In}$ as a model-sensitive $(\gamma ,p)/(\gamma ,n)$ branching point within the $\gamma$ process. Constraining the involved reaction rates may have a significant impact on the predicted $p$-nuclei abundances. Here we report on measurements of the cross sections for ${}^{102}\mathrm{Pd}(p,\gamma ){}^{103}\mathrm{Ag},{}^{108}\mathrm{Cd}(p,\gamma ){}^{109}\mathrm{In}$, and ${}^{110}\mathrm{Cd}(p,\gamma ){}^{111}\mathrm{In}$ reactions for proton laboratory energies 3–8 MeV using the high efficiency total absorption spectrometer and the $\gamma$-summing technique. These measurements were used to constrain Hauser-Feshbach parameters used in talys 1.9, which constrains the ${}^{111}\mathrm{In}(\gamma ,p){}^{110}\mathrm{Cd}$ and ${}^{111}\mathrm{In}(\gamma ,n){}^{110}\mathrm{Ag}$ reaction rates. The newly constrained reaction rates indicate that the ${}^{111}\mathrm{In}(\gamma ,p)/(\gamma ,n)$ branching point occurs at a temperature of $2.71\pm 0.05\mathrm{GK}$, well within the temperature range relevant to the $\gamma$ process. These findings differ significantly from previous studies and may impact the calculated abundances.

Background: This is the third of a series of papers on baryon-baryon (BB) interactions, where the baryons are the lowest lying baryon states with spin and parity $J^P={(1/2)}^{+}$. The paper presents the extended-soft-core (ESC) model ESC16 for BB channels with strangeness $S=-2$.

Purpose: The aim is to describe the ingredients of the $S=-2$ ESC16 potentials, to apply these two-body interactions to BB scattering and via $G$-matrix calculations to hypernuclear systems, and to compare with the presently available experimental information.

Methods:The potentials for $S=-2$ are based on the SU(3) extension of the ESC potentials for the strangeness $S=0$ and $S=-1$ sectors, which are fitted to experimental nucleon-nucleon ($NN$), hyperon-nucleon ($YN$), and hyperon-hyperon ($YY$) data. Flavor SU(3) symmetry is broken only ‘kinematically’ by the masses of the baryons and the mesons. For the $S=-2$ channels almost no experimental scattering data exist, and the information from hypernuclei is also rather limited. Nevertheless, in the fit to the $S=0$ and $S=-1$ sectors information from the Nagara event and the scarce experimental results on the $\mathrm{\Xi }N$ cross sections have been used as (mild) constraints to determine the free parameters in the simultaneous fit of the deuteron and the $NN\oplus YN$ scattering data. Therefore, the potentials for the $S=-2$ sectors are almost completely determined by the fits to the $NN, YN$ data, and SU(3) symmetry.

Results: Various properties of the $S=-2$ potentials are illustrated by giving results for scattering lengths, bound states, phase parameters, and total cross sections. The well-depth $U_{\mathrm{\Xi }}$ is calculated and $\mathrm{\Xi }N G$-matrix interactions are derived and applied to ${\mathrm{\Xi }}^{-}$-capture reactions. Here, a phenomenological $\mathrm{\Xi }N$ interaction is added to describe the experiments. Furthermore, the ESC16 model supplemented with phenomenological SU(3) symmetric gaussian interactions is analyzed, and attractive $\mathrm{\Xi }N$ interactions are obtained. Combined with three-body forces derived from the ESC meson-pair vertices and the Fujita-Miyazawa interaction, yields good baryon well depths.

Conclusions: The ESC16 $S=-2$ potentials, with kinematically broken SU(3) symmetry, provide a basis for realistic calculations in nuclear and hypernuclear physics. For a successful description of the well depth's $U_N,U_{\mathrm{\Lambda }},U_{\mathrm{\Sigma }}$, and $U_{\mathrm{\Xi }}$ and hypernuclear $S=-2$ reactions phenomenological additions are needed.

We report in this paper a study in terms of the nuclear shell model about the location of the calcium isotopes drip line. The starting point is considering the realistic two-body potential derived by Entem and Machleidt within chiral perturbation theory at next-to-next-to-next-to-leading order (${\mathrm{N}}^3\mathrm{LO}$), as well as a chiral three-body force at next-to-next-to-leading order (${\mathrm{N}}^2\mathrm{LO}$) whose structure and low-energy constants are consistent with the two-body potential. Then we construct the effective single-particle energies and residual interaction needed to diagonalize the shell-model Hamiltonian. The calculated two-neutron separation energies agree nicely with experiment until ${}^{56}\mathrm{Ca}$, which is the heaviest isotope whose mass has been measured, and do not show any sign of two-neutron emission until ${}^{70}\mathrm{Ca}$. We discuss the role of the choice of the model space in determining the neutron drip line, and also the dependence of the results on the parameters of the shell-model Hamiltonian.

The evolution of nonhydrodynamic slow processes near the QCD critical point is explored with the novel $\mathrm{hydro}+$ framework, which extends the conventional hydrodynamic description by coupling it to additional explicitly evolving slow modes describing long wavelength fluctuations. Their slow relaxation is controlled by critical behavior of the correlation length and is independent from gradients of matter density and pressure that control the evolution of the hydrodynamic quantities. In this exploratory study, we follow the evolution of the slow modes on top of a simplified QCD matter background, allowing us to clearly distinguish and study, both separately and in combination, the main effects controlling the dynamics of critical slow modes. In particular, we show how the evolution of the slow modes depends on their wave number, the expansion of and advection by the fluid background, and the behavior of the correlation length. Nonequilibrium contributions from the slow modes to bulk matter properties that affect the bulk dynamics (entropy, pressure, temperature, and chemical potential) are discussed and found to be small.

We study the mass-dependent hierarchy of kinetic freeze-out parameters of hadrons in low-energy heavy-ion collisions. For this purpose, the transverse momentum and rapidity spectra of the identified hadrons produced in central $\mathrm{Pb}+\mathrm{Pb}$ collisions, available at super proton synchrotron energies ranging from $E_{\text{Lab}}=20A–158A$ GeV, are analyzed within a generalized non-boost-invariant blast-wave model. We consider separate simultaneous fits for light hadrons (${\pi }^{-}, K^{\pm }$) and heavy strange hadrons ($\mathrm{\Lambda }, \overline{\mathrm{\Lambda }}, \varphi , {\mathrm{\Xi }}^{\pm }, {\mathrm{\Omega }}^{\pm }$), for which the transverse momentum spectra as well as rapidity spectra are available. We also perform a separate fit to transverse momentum spectra of charmonia ($J/\mathrm{\Psi }, {\mathrm{\Psi }}^{\prime }$) at $158A$ GeV collisions. We find a clear mass-dependent hierarchy in the fitted kinetic freeze-out parameters. Further, we study the rapidity spectra using analytical Landau flow solution for nonconformal systems. We find that the fitted value of sound velocity in the medium also shows a similar hierarchy.

We compute the charge radii and ground-state energies of even-mass neon and magnesium isotopes from neutron number $N=8$ to the dripline. Our calculations are based on nucleon-nucleon and three-nucleon potentials from chiral effective field theory that include $\mathrm{\Delta }$ isobars. These potentials yield an accurate saturation point and symmetry energy of nuclear matter. We use the coupled-cluster method and start from an axially symmetric reference state. Binding energies and two-neutron separation energies largely agree with data, and the dripline in neon is accurate. The computed charge radii are accurate for many isotopes where data exist. Finer details, such as isotope shifts, however, are not accurately reproduced. These chiral potentials indicate a subshell closure at $N=14$ for the radii (but not for two-neutron separation energies) and a decrease in charge radii at $N=8$ (observed in neon and predicted for magnesium). They yield a continued increase of charge radii as neutrons are added beyond $N=14$ yet underestimate the large increase at $N=20$ in magnesium.

Differential cross sections for the deuteron breakup ${}^1\mathrm{H}(d,pp)n$ reaction were measured for a large set of 243 geometrical configurations at the beam energy of 80 MeV/nucleon. The cross-section data are normalized by the luminosity factor obtained on the basis of a simultaneous measurement of the elastic-scattering channel and the existing cross-section data for this process. The results are compared with the theoretical calculations modeling nuclear interactions with and without taking into account the three-nucleon force (3NF) and the Coulomb interaction. In the validated region of the phase space, both the Coulomb force and 3NF play an important role in providing a good description of the data. There are also regions in which description improvements due to the inclusion of 3NF are insufficient.

Fission-fragment mass distributions for 23 nuclei (${}^{234-237}\mathrm{U}$, ${}^{236-239}\mathrm{Np}$, ${}^{238-241}\mathrm{Pu}$, ${}^{240-243}\mathrm{Am}$, ${}^{242-245}\mathrm{Cm}$, and ${}^{244-246}\mathrm{Bk}$) were measured using the multinucleon transfer approach in the reaction of ${}^{18}\mathrm{O}+{}^{237}\mathrm{Np}$, and their excitation-energy dependence was obtained up to a maximum of 70 MeV. Among them, the low-energy fission of ${}^{236}\mathrm{Np}$, ${}^{238}\mathrm{Pu}$, and ${}^{245}\mathrm{Cm}$ is reported for the first time. The experimental data for all the studied nuclei were compared to the Langevin calculations. The calculation which takes into account the effects of multichance fission well reproduced the peak-to-valley ratio and mass-asymmetric peak positions of the distributions. The angular momentum given to the fissioning nucleus is also discussed.

A high-precision branching ratio measurement for the superallowed Fermi ${\beta }^{+}$ emitter ${}^{62}\mathrm{Ga}$ was performed with the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high efficiency of the GRIFFIN spectrometer allowed 63 $\gamma$-ray transitions, with intensities down to $\approx 1$ part per million (ppm) per ${}^{62}\mathrm{Ga}{\beta }^{+}$ decay, to be placed in the level scheme of the daughter nucleus ${}^{62}\mathrm{Zn}$, establishing the superallowed $\beta$ branching ratio for ${}^{62}\mathrm{Ga}$ decay to be $99.{8577}_{-0.0029}^{+0.0023}\%$, a factor of 4 more precise than the previous world average. For several cascades, $\gamma \text{−}\gamma$ angular correlation measurements were performed to assign spins and/or determine the mixing ratios of transitions. In particular, the spin of the 2.342 MeV excited state in the daughter nucleus ${}^{62}\mathrm{Zn}$ was definitively assigned as $J=0$. This assignment resolves a discrepancy between previous measurements and has important implications for the isospin symmetry breaking correction, ${\delta }_{C1}$, in ${}^{62}\mathrm{Ga}$ superallowed Fermi $\beta$ decay.

We measured absolute cross sections for neutron transfer channels populated in the ${}^{94}\mathrm{Rb}+{}^{208}\mathrm{Pb}$ binary reaction. Cross sections have been extracted identifying directly the lead isotopes with the high efficiency MINIBALL $\gamma$-ray array coupled to a particle detector combined with a radioactive ${}^{94}\mathrm{Rb}$ beam delivered at $E_{\mathrm{lab}}=6.2$ MeV/nucleon by the HIE-ISOLDE facility. We observed sizable cross sections in the neutron-rich mass region, where the heavy partner acquires neutrons. A fair agreement between the measured cross sections with those from GRAZING calculations gives confidence in the cross-section predictions of more neutron-rich nuclei produced via a larger number of transferred nucleons.

We present direct photon-hadron correlations in 200 GeV/$A$ $\mathrm{Au}+\mathrm{Au}$, $d+\mathrm{Au}$, and $p+p$ collisions, for direct photon $p_T$ from 5–12 $\mathrm{GeV}/c$, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in $d+\mathrm{Au}$ collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in $\mathrm{Au}+\mathrm{Au}$ compared to $p+p$ and $d+\mathrm{Au}$. As the momentum fraction decreases, the yield of hadrons in $\mathrm{Au}+\mathrm{Au}$ increases to an excess over the yield in $p+p$ collisions. The excess is at large angles and at low hadron $p_T$ and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.

The evolution of the hot and rotating ${}^{43}\mathrm{Sc}$ nucleus to a highly deformed shape has been studied by measuring the high-energy $\gamma$ rays from the decay of the giant dipole resonance. The compound nucleus was populated at two initial excitation energies and average angular momenta of $\approx 26$ and $31\hslash$ by using ${}^{16}\mathrm{O}$ beam of energies $E_{\mathrm{lab}}$ = 120 and 142 MeV, respectively. The evaporated neutron energy spectra have been measured for proper determination of nuclear level density. The angular momentum has been determined by measuring the low-energy $\gamma$-ray multiplicities. The high-energy $\gamma$-ray and neutron spectra were analyzed simultaneously. At $\langle J\rangle \approx 26\hslash$ a near-oblate shape is observed, whereas at $\langle J\rangle \approx 31\hslash$ a sharp peak is observed at $E_{\gamma }\approx 10\mathrm{MeV}$ pointing towards the transition to the Jacobi shape with quadruple deformation parameter $\beta \approx 0.7$. The results have been corroborated by the theoretical calculations based on the rotating liquid drop model framework.

Medium and high spin states of the ${}^{96}\mathrm{Y}$ nucleus, located in the shape-coexistence region near $Z=40$ and $N=60$, were populated in thermal-neutron-induced fission of ${}^{233}\mathrm{U}$ and ${}^{235}\mathrm{U}$ targets, diluted in a scintillator. $\gamma$ rays were measured with the FIssion Product Prompt $\gamma$-ray Spectrometer (FIPPS) high-purity germanium (HPGe) detector array, using double and triple $\gamma$-ray coincidence techniques and taking advantage of the efficient fission tag provided by the scintillating target material. A complex level scheme, extending up to 5.2 MeV and including excitations above the $8^{+}\beta$-decaying isomer, was investigated, and firm spin and parity assignments were given to a number of states, on the basis of angular correlation analysis and considerations on the $\gamma$-decay patterns. While the structures built on the $0^{-}$ ground state and the $8^{+}$ isomer show irregular patterns typical for spherical shapes, the ($6^{+}$) isomeric state at 1655 keV [with half-life of 181(9) ns], and the rotational band built on it [with spin-parity values between ($6^{+}$) and ($9^{+}$)], can be explained by Hartree-Fock-Bogoliubov calculations, if an oblate deformation is assumed. This is the first observation of a deformed structure in an $N=57$ isotone, lying three neutrons away from the $N=60$ line. An important finding is also the 115-keV transition which connects the ($6^{+}$) 181(9)-ns isomer to the $\beta$-decaying $8^{+}$ spherical isomer, allowing us to firmly place the latter at 1541 keV excitation energy. This may be relevant for calculations of electron and antineutrino spectra from fission of actinides, for which ${}^{96}\mathrm{Y}$ is a prominent product.