An interpretation of the ridge phenomenon found in $\mathit{pp}$ collisions at 7 TeV is given in terms of enhancement of soft partons due to energy loss of semihard jets. A description of ridge formation in nuclear collisions can directly be extended to $\mathit{pp}$ collisions since hydrodynamics is not used and azimuthal anisotropy is generated by semihard scattering. The observed ridge structure is then understood as a manifestation of soft-soft transverse correlation induced by semihard partons without long-range longitudinal correlation. Both the $p_T$ and multiplicity dependencies are well reproduced. Some predictions are made about other observables.

A hybrid transport approach for the bulk evolution of viscous QCD matter produced in ultra-relativistic heavy-ion collisions is presented. The expansion of the dense deconfined phase of the reaction is modeled with viscous hydrodynamics, while the dilute late hadron gas stage is described microscopically by the Boltzmann equation. The advantages of such a hybrid approach lie in the improved capability of handling large dissipative corrections in the late dilute phase of the reaction, including a realistic treatment of the nonequilibrium hadronic chemistry and kinetic freeze-out. By varying the switching temperature at which the hydrodynamic output is converted to particles for further propagation with the Boltzmann cascade we test the ability of the macroscopic hydrodynamic approach to emulate the microscopic evolution during the hadronic stage and extract the temperature dependence of the effective shear viscosity of the hadron resonance gas produced in the collision. We find that the extracted values depend on the prior hydrodynamic history and hence do not represent fundamental transport properties of the hadron resonance gas. We conclude that viscous fluid dynamics does not provide a faithful description of hadron resonance gas dynamics with predictive power, and that both components of the hybrid approach are needed for a quantitative description of the fireball expansion and its freeze-out.

Photoabsorption cross sections of Nd and Sm isotopes from spherical to deformed even nuclei are systematically investigated by means of the quasiparticle-random-phase approximation based on the Hartree-Fock-Bogoliubov ground states using the Skyrme energy density functional. The gradual onset of deformation in the ground states as the neutron number increases leads to characteristic features of the shape phase transition. The calculations well reproduce the isotopic dependence of broadening and the emergence of a double-peak structure in the cross sections without any adjustable parameter. We also find that the deformation plays a significant role for low-energy dipole strengths. The $E1$ strengths are fragmented and considerably lowered in energy. The summed $E1$ strength up to 10 MeV is enhanced by a factor of 5 or more.

The structure of ${}^{72}\mathrm{Se}$ was investigated following the $\epsilon /{\beta }^{+}$ decay of ${}^{72}\mathrm{Br}$ produced in the ${}^{58}\mathrm{Ni}$(${}^{16}\mathrm{O}$, $\mathit{pn}$) reaction at 50 MeV. Using a beam chopping system, off-beam $\gamma$-ray decay data was collected with an array of clover Ge detectors. $\gamma$-$\gamma$ coincidence measurements provided a significant modification of the prior level scheme, and $\gamma$-$\gamma$ angular correlation measurements allowed spin determinations and multipole mixing ratio extraction. The new information on the non-yrast states was combined with previous in-beam data to investigate the issue of shape coexistence by comparing to various configuration mixing approaches. Clear evidence for shape coexistence is found, with a ground state of modest, or slightly oblate, deformation and a well-deformed prolate shape that would lie at an unperturbed excitation of 875 keV. The shape mixing is near complete at low spin.

The PHENIX experiment at the Relativistic Heavy Ion Collider has performed systematic measurements of $\varphi$ meson production in the $K^{+}{K}^{-}$ decay channel at midrapidity in $p+p$, $d+\mathrm{Au}$, $\mathrm{Cu}+\mathrm{Cu}$, and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{\mathit{NN}}}}=200\hspace{0.5em}\mathrm{GeV}$. Results are presented on the $\varphi$ invariant yield and the nuclear modification factor $R_{\mathrm{AA}}$ for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$, and $R_{\mathrm{dA}}$ for $d+\mathrm{Au}$ collisions, studied as a function of transverse momentum ($1<p_T<7\hspace{0.5em}\mathrm{GeV}/c$) and centrality. In central and midcentral $\mathrm{Au}+\mathrm{Au}$ collisions, the $R_{\mathrm{AA}}$ of $\varphi$ exhibits a suppression relative to expectations from binary scaled $p+p$ results. The amount of suppression is smaller than that of the ${\pi }^0$ and the $\eta$ in the intermediate $p_T$ range ($2-5\hspace{0.5em}\mathrm{GeV}/c$), whereas, at higher $p_T$, the $\varphi$, ${\pi }^0$, and $\eta$ show similar suppression. The baryon (proton and antiproton) excess observed in central $\mathrm{Au}+\mathrm{Au}$ collisions at intermediate $p_T$ is not observed for the $\varphi$ meson despite the similar masses of the proton and the $\varphi$. This suggests that the excess is linked to the number of valence quarks in the hadron rather than its mass. The difference gradually disappears with decreasing centrality, and, for peripheral collisions, the $R_{\mathrm{AA}}$ values for both particle species are consistent with binary scaling. $\mathrm{Cu}+\mathrm{Cu}$ collisions show the same yield and suppression as $\mathrm{Au}+\mathrm{Au}$ collisions for the same number of $N_{\mathrm{part}}$. The $R_{\mathrm{dA}}$ of $\varphi$ shows no evidence for cold nuclear effects within uncertainties.

The directed flow of particles emitted from the fireball created in a heavy-ion collision is shown to be a very sensitive measure of the pressure equilibration in the first 1 fm/c of the evolution. Performing a $(3+1)$-dimensional relativistic hydrodynamic calculation with nonequilibrated longitudinal and transverse pressures, we show that the directed flow is strongly reduced if the pressure imbalance survives for even a short time. Transverse momentum spectra, elliptic flow, and interferometry correlation radii are not very sensitive to this early pressure anisotropy. Comparison with the data points toward a short equilibration time of the order of $0.25$ fm/c or less.

In a previous article, the four-dimensional (4D) half-Skyrmion (or five-dimensional dyonic salt) structure of dense baryonic matter described in crystalline configuration in the large $N_c$ limit was shown to have nontrivial consequences on how antikaons behave in compressed nuclear matter with a possible implication for the “ice-9” phenomenon of deeply bound kaonic matter and condensed kaons in compact stars. We extend the analysis to make a further prediction on the scaling properties of hadrons that have a surprising effect on the nuclear tensor forces, the symmetry energy, and hence on the phase structure at high density. We treat this problem, relying on certain topological structures of chiral solitons. Combined with what can be deduced from hidden local symmetry for hadrons in a dense medium and the “soft” dilatonic degree of freedom associated with the trace anomaly of QCD, we uncover a novel structure of chiral symmetry in the “supersoft” symmetry energy that can influence the structure of neutron stars.

The study of the path-length dependence of high-transverse-momentum ($P_T$) hadron suppression in heavy-ion collisions by measuring the dependence of hard-hadron production on the angle $\varphi$ with the reaction plane in noncentral collisions has so far been one of the most successful tools in constraining the microscopic picture of leading-parton energy loss. With the imminent start of the Large Hadron Collider heavy-ion program and the possibility of full jet reconstruction, the focus has shifted to models that are capable of simulating full in-medium parton showers rather than tracing the leading parton only. Yet, on the level of single-inclusive hadron observables, such shower models need to reproduce the findings of leading-parton energy-loss models; in particular, they need to reproduce the correct reaction-plane-angle dependence of hadron suppression. The aim of this work is to illustrate, using the example of the Monte Carlo in-medium shower code, yajem (Yet another Jet Energy-loss Model), how path-length dependence arises in a Monte Carlo shower formulation, how it relates to path-length dependence of leading-parton energy loss, and how model results compare with data on the reaction-plane dependence of the nuclear suppression factor $R_{\mathit{AA}}(\varphi )$.

We calculate the screening of the ion-ion potential due to electrons, in the presence of a large background magnetic field, at densities of relevance to neutron star crusts. Using the standard approach to incorporate electronic screening through the one-loop polarization function, we show that the magnetic field produces important corrections at both short and long distances. In extreme fields, realized in highly magnetized neutron stars called magnetars, electrons occupy only the lowest Landau levels in the relatively low-density region of the crust. Here our results show that the screening length for Coulomb interactions between ions can be smaller than the inter-ion spacing. More interestingly, we find that the screening is anisotropic, and the screened potential between two static charges exhibits long-range Friedel oscillations parallel to the magnetic field. This long-range oscillatory behavior is likely to affect the lattice structure of ions and can possibly create anisotropic structures in the magnetar crusts. We also calculate the imaginary part of the electron polarization function, which determines the spectrum of electron-hole excitations and plays a role in damping lattice phonon excitations. We demonstrate that even for modest magnetic fields this damping is highly anisotropic and will likely lead to anisotropic phonon heat transport in the outer neutron star crust.

We perform Brueckner-Hartree-Fock calculations of hypernuclear matter at finite temperature and provide convenient analytical parametrizations of the results. We then study the properties of (proto)neutron stars containing hyperons. We find important effects of trapping and finite temperature on the structure of hyperonic stars.

The high spin states of ${}^{112}\mathrm{In}$ have been investigated with in-beam $\gamma$-ray spectroscopic methods using the ${}^{110}\mathrm{Pd}$$({}^7\mathrm{Li},5n)$${}^{112}\mathrm{In}$ reaction at a beam energy of 50 MeV. A level scheme with three band structures has been established and their configurations are discussed. The positive-parity dipole band has been assigned as a magnetic rotation band. Particle-rotor model calculations have also been performed to interpret the rotational structures in ${}^{112}\mathrm{In}$.

We have measured the elastic scattering of the weakly bound ${}^6\mathrm{Li}$ on the ${}^{116,112}\mathrm{Sn}$ targets, at energies close to the Coulomb barrier. The energy dependence of the interaction potential has been investigated by two different methods and the presence of the breakup threshold anomaly is observed. We have also derived the total reaction cross sections for the above systems and compared them to those of other systems with halo, weakly bound, and tightly bound projectiles on targets with similar masses. The reaction cross sections are largest for systems with halo nuclei, then the systems with no-halo weakly bound nuclei, and the smallest cross sections are those for tightly bound systems.

The nucleus-nucleus interaction potential has been studied within the relativistic mean field theory. The systematics of the relativistic effects have been investigated by analyzing the relation between the potential and the bombarding energy as a function of the impact parameter. It is shown that the potential barriers are noticeably sensitive to the bombarding energy for a given impact parameter. At large bombarding energies, the slope at the potential edge decreases with the impact parameter. Comparisons with a nonrelativistic treatment shows that relativistic effects cannot be ignored at bombarding energies around and larger than 100 MeV/nucleon.

Using the AMPT model for relativistic heavy ion collisions, we have studied the di-hadron azimuthal angular correlations triggered by emitted jets in $\text{Au}+\text{Au}$ collisions at center-of-mass energy $\sqrt{s_{\mathit{NN}}}=200$ GeV and impact parameter $b=8$ fm. A double-peak structure for the associated particles at the away side of trigger particles is obtained after subtracting background correlations due to the elliptic flow. Both the near-side peak and the away-side double peaks in the azimuthal angular correlations are, however, significantly suppressed (enhanced) in events of small (large) triangular flow or triangularity in the initial collision geometry as a result of fluctuations. After subtraction of background correlations due to the triangular flow, the away-side double peaks change into a single peak with broad shoulders on both sides. The away side of the di-hadron correlations becomes essentially a single peak after further subtraction of higher-order flows.

Low-lying energy states of the ${}^{147-153}\text{Pm}$ isotopic chain are studied within the framework of the neutron-proton interacting boson-fermion model (IBFM-2). The spectra of these isotopes show a transition from a particle coupled to a vibrational core to a particle coupled to a deformed one. The calculation reproduces this behavior. In addition, reduced transition probabilities $B(E2)$ and $B(M1)$ and quadrupole and magnetic moments, as well as spectroscopic factors corresponding to stripping and pickup transfer reactions, are calculated. Obtained results compare well with the available experimental data, which reinforces the reliability of the wave functions obtained within the IBFM-2 model.

We study the latent heat of the liquid-gas phase transition in symmetric nuclear matter using self-consistent mean-field calculations with a few Skyrme forces. The temperature dependence of the latent heat is rather independent of the mean-field parametrization and it can be characterized by a few parameters. At low temperatures, the latent heat tends to the saturation energy. Near the critical point, the latent heat goes to zero with a well-determined mean-field critical exponent. A maximum value of the latent heat in the range $l~25–30$ MeV is found at intermediate temperatures, which might have experimental relevance. All these features can be explained from very basic principles.

New angular distributions for the ${}^7\mathrm{Li}$(${}^{18}\mathrm{O}$,${}^{17}\mathrm{N}$)${}^8\mathrm{Be}$ reaction at an energy of $E_{\text{lab}}$(${}^{18}\mathrm{O}$)$=$114 MeV for the ground states of ${}^8\mathrm{Be}$ and ${}^{17}\mathrm{N}$ and the excited states of ${}^{17}\mathrm{N}$ were measured. These data and ${}^{18}\mathrm{O}$($d,{}^3$He)${}^{17}\mathrm{N}$ reaction data taken at $E_d=52$ MeV were analyzed within the coupled-reaction-channels method using ${}^7\mathrm{Li}+{}^{18}\mathrm{O}$ and ${}^{18}\mathrm{O}$ + $d$ optical potentials deduced from previous elastic and inelastic scattering results. Shell-model spectroscopic amplitudes were used in the analysis. Both reactions are dominated by single proton transfer. Calculations show that heavy-ion reactions of the type studied in this work can be used to identify final-state spins when measurements are carried to small angles.

We study the perturbative renormalizability of chiral two-pion exchange for singlet and triplet channels within effective field theory, provided that the one-pion exchange piece of the interaction has been fully iterated. We determine the number of counterterms/subtractions needed to obtain finite results when the cutoff is removed, resulting in three counterterms for the singlet channel and six for the triplet. The results show that perturbative chiral two-pion exchange reproduce the data up to a center-of-mass momentum of $k~200–300$ MeV in the singlet channel and $k~300–400$ MeV in the triplet.