The phase transition of hadronic to quark matter at high baryon and isospin density is analyzed. Relativistic mean-field models are used to describe hadronic matter, and the MIT bag model is adopted for quark matter. The boundaries of the mixed phase and the related critical points for symmetric and asymmetric matter are obtained. Due to the different symmetry term in the two phases, isospin effects appear to be rather significant. With increasing isospin asymmetry the binodal transition line of the ($T,{\rho }_B$) diagram is lowered to a region accessible through heavy-ion collisions in the energy range of the new planned facilities (e.g., the FAIR/NICA projects). Some observable effects are suggested, in particular an isospin distillation mechanism with a more isospin asymmetric quark phase, to be seen in charged meson yield ratios, and an onset of quark number scaling of the meson-baryon elliptic flows. The presented isospin effects on the mixed phase appear to be robust with respect to even large variations of the poorly known symmetry term at high baryon density in the hadron phase. The dependence of the results on a suitable treatment of isospin contributions in effective QCD Lagrangian approaches, at the level of explicit isovector parts and/or quark condensates, is discussed.

Two novel QCD effects, double-color filtering and mutual boosting of the saturation scales in colliding nuclei, affect the transparency of the nuclei for quark dipoles in comparison with proton-nucleus collisions. The former effect increases the survival probability of the dipoles, since color filtering in one nucleus makes the other one more transparent. The second effect acts in the opposite direction and is stronger; it makes the colliding nuclei more opaque than in the case of $\mathit{pA}$ collisions. As a result of parton saturation in nuclei the effective scale is shifted upward, which leads to an increase of the gluon density at small $x$. This in turn leads to a stronger transverse momentum broadening in $\mathit{AA}$ compared with $\mathit{pA}$ collisions, i.e., to an additional growth of the saturation momentum. Such a mutual boosting leads to a system of reciprocity equations, which result in a saturation scale, a few times higher in $\mathit{AA}$ than in $\mathit{pA}$ collisions at the energies of the large hadron collider (LHC). Since the dipole cross section is proportional to the saturation momentum squared, the nuclei become much more opaque for dipoles in $\mathit{AA}$ than in $\mathit{pA}$ collisions. For the same reason gluon shadowing turns out to be boosted to a larger magnitude compared with the product of the gluon shadowing factors in each of the colliding nuclei. All these effects make it more difficult to establish a baseline for anomalous $J/\Psi$ suppression in heavy ion collisions at high energies.

A sensitive search for isotopes of a superheavy element (SHE) in natural gold materials has been performed with accelerator mass spectrometry at the Vienna Environmental Research Accelerator, which is based on a 3-MV tandem accelerator. Because the most likely SHE in gold is roentgenium (Rg, $Z$ $=$ 111), the search concentrated on Rg isotopes. Two different mass regions were explored: (i) For the neutron-deficient isotopes  ${}^{261}\mathrm{Rg}$ and ${}^{265}\mathrm{Rg}$, abundance limits in gold of $3\times {10}^{-16}$ were reached (no events observed). This is in stark contrast to the findings of Marinov et al. [Int. J. Mod. Phys. E 18, 621 (2009)], who reported positive identification of these isotopes with inductively coupled plasma sector field mass spectrometry in the $(1-10)\times {10}^{-10}$ abundance range. (ii) Theoretical models of SHEs predict a region of increased stability around the proton and neutron shell closures of $Z$ $=$ 114 and $N$ $=$ 184. We therefore investigated eight heavy Rg isotopes, ${}^A$Rg, $A$ $=$ 289, 290, 291, 292, 293, 294, 295, and 296. For six isotopes no events were observed, setting limits also in the ${10}^{-16}$ abundance range. For ${}^{291}\mathrm{Rg}$ and ${}^{294}\mathrm{Rg}$ we observed two and nine events, respectively, which results in an abundance in the ${10}^{-15}$ range. However, pileup of a particularly strong background in these cases makes a positive identification as Rg isotopes—even after pileup correction—unlikely.

A relativistic formula is derived for the self-energy of $\rho$ meson in nuclear matter from a baryonic loop graph containing nucleon and $\Delta (1232)$. After identifying the Lindhard function, we find another term in it that contributes appreciably to the real part of the self-energy. We also note small errors that may appear in the numerical calculation owing to the use of incorrect $\Delta$ coupling with other fields and presence of quadratic distribution functions in the self-energy formula.

The structure of proton-unbound ${}^{30}\mathrm{S}$ states strongly determines the thermonuclear ${}^{29}\mathrm{P}$($p,\gamma$)${}^{30}\mathrm{S}$ reaction rate at temperatures characteristic of explosive hydrogen burning in classical novae and type I x-ray bursts. Specifically, the rate had been previously predicted to be dominated by two low-lying, unobserved, levels in the $E_x=$ 4.7–4.8 MeV region, with spin and parity assignments of 3${}^{+}$ and 2${}^{+}$. In recent experimental work, two candidate levels were observed with energies of 4.699 MeV and 4.814 MeV, but no experimental information on their spins and parities was obtained. We have performed an in-beam $\gamma$-ray spectroscopy study of ${}^{30}\mathrm{S}$ with the ${}^{28}\mathrm{Si}$(${}^3\mathrm{He}$, $n\gamma$)${}^{30}\mathrm{S}$ reaction. By constructing the decay schemes of proton-unbound states with a $\gamma$-$\gamma$ coincidence analysis of their decay $\gamma$ rays, their $J^{\pi }$ values were inferred from a comparison to the known decay schemes of the corresponding mirror states in ${}^{30}\mathrm{Si}$. For the two aforementioned states, our results strongly corroborate the spin-parity assignments assumed in recent evaluations of the ${}^{29}\mathrm{P}$($p,\gamma$)${}^{30}\mathrm{S}$ reaction rate.

A new method is presented for the quantitative measurement of charge separation about the reaction plane. A correlation function is obtained whose shape is concave when there is a net separation of positive and negative charges. Correlations not specifically associated with charge, from flow, jets, and momentum conservation, do not influence the shape or magnitude of the correlation function. Detailed simulations are used to demonstrate the effectiveness of the method for the quantitative measurement of charge separation. Such measurements are a prerequisite to the investigation of topological charge effects in the quark-gluon plasma as derived from the “strong $\mathcal{CP}$ problem.”

Modern electron scattering experiments have determined the proton electric form factor $G_{\mathit{Ep}}(Q^2)$ to high precision. We utilize this data, represented by the different empirical form-factor parametrizations, to compute the third Zemach moment of the proton charge distribution. We find that existing data rule out a value of the third Zemach moment large enough to explain the current puzzle with the proton charge radius, determined from the Lamb shift in muonic hydrogen. This is in contrast to the recent paper of De Rújula. We also demonstrate that the size of the third Zemach moment is largely governed by the fourth moment of the conventional charge distributions $\langle r^4\rangle$, which enables us to obtain a rigorous upper bound on the magnitude of the third Zemach moment of the proton.

Fully consistent axially-symmetric deformed quasiparticle random-phase approximation (QRPA) calculations have been performed, using the same Gogny D1S effective force for both the Hartree-Fock-Bogolyubov mean field and QRPA matrix. New implementation of this approach leads to the applicability of QRPA to heavy deformed nuclei. Giant resonances and low-energy collective states for monopole, dipole, quadrupole, and octupole modes are predicted for the heavy deformed nucleus ${}^{238}\mathrm{U}$ and compared with experimental data.

Excited states in ${}^{251}\mathrm{Fm}$ populated via the $\alpha$ decay of ${}^{255}\mathrm{No}$ are studied in detail through $\alpha$-$\gamma$ coincidence and $\alpha$ fine-structure measurements. Five excited states reported previously in ${}^{251}\mathrm{Fm}$ are firmly established through the $\alpha$-$\gamma$ coincidence measurement, and rotational bands built on one-quasiparticle states are newly established through the $\alpha$ fine-structure measurement. Spin-parities and neutron configurations of the excited states in ${}^{251}\mathrm{Fm}$ as well as the ground state of ${}^{255}\mathrm{No}$ are definitely identified on the basis of deduced internal conversion coefficients, lifetimes of $\gamma$ transitions, rotational-band energies built on one-quasiparticle states, and hindrance factors of $\alpha$ transitions. It is found that the excitation energy of the 1/2${}^{+}$[620] state in $N=151$ isotones increases with the atomic number, especially at $Z⩾100$, while that of the 1/2${}^{+}$[631] state decreases at $Z=100$. Ground-state deformations and energies of neutron one-quasiparticle states in the $N=151$ isotones are calculated using a macroscopic-microscopic model, and the energy systematics of the one-quasiparticle states in the isotones are discussed in terms of the evolution of nuclear deformation involving the hexadecapole (${\beta }_4$) and hexacontatetrapole (${\beta }_6$) deformations.

Single-neutron-transfer measurements using ($p$,$d$) reactions have been performed at 33 MeV per nucleon with proton-rich ${}^{34}\mathrm{Ar}$ and neutron-rich ${}^{46}\mathrm{Ar}$ beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between ${}^{34}\mathrm{Ar}$ and ${}^{46}\mathrm{Ar}$. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of ${}^{40-49}\mathrm{Ca}$ isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.

The event-plane method, which is widely used to analyze anisotropic flow in nucleus-nucleus collisions, is known to be biased by nonflow effects, especially at high $p_t$. Various methods (cumulants, Lee-Yang zeros) have been proposed to eliminate nonflow effects, but their implementation is tedious, which has limited their application so far. In this article, we show that the Lee-Yang-zeroes method can be recast in a form similar to the standard event-plane analysis. Nonflow correlations are strongly suppressed by using the information from the length of the flow vector, in addition to the event-plane angle. This opens the way to improved analyses of elliptic flow and azimuthally sensitive observables at the Relativistic Heavy Ion Collider and the Large Hadron Collider.

Electron antineutrinos are commonly detected in liquid scintillator experiments via inverse $\beta$ decay by looking at the coincidence between the reaction products: neutrons and positrons. Prior to positron annihilation, an electron-positron pair may form an orthopositronium (o-Ps) state, with a mean lifetime of a few nanoseconds. Even if the o-Ps decay is speeded up by spin-flip or pick-off effects, it may introduce distortions in the photon emission time distribution, crucial for position reconstruction and pulse shape discrimination algorithms in antineutrino experiments. Reversing the problem, the o-Ps-induced time distortion represents a new signature for tagging antineutrinos in liquid scintillator. In this article, we report the results of measurements of the o-Ps formation probability and lifetime for the most used solvents for organic liquid scintillators in neutrino physics (pseudocumene, linear alkyl benzene, phenylxylylethane, and dodecane). We characterize also a mixture of pseudocumene $+$1.5 g/l of 2,5-diphenyloxazole, a fluor acting as wavelength shifter. In the second part of the article, we demonstrate that the o-Ps-induced distortion of the scintillation photon emission time distributions represent an optimal signature for tagging positrons on an event by event basis, potentially enhancing the antineutrino detection.

Particle-$\gamma$ coincidences from the ${}^{46}\mathrm{Ti}$($p,p^{\prime }\gamma$)${}^{46}\mathrm{Ti}$ inelastic scattering reaction with 15-MeV protons are utilized to obtain $\gamma$-ray spectra as a function of excitation energy. The rich data set allows analyzsis of the coincidence data with various gates on excitation energy. For many independent data sets, this enables a simultaneous extraction of level density and radiative strength function (RSF). The results are consistent with one common level density. The data seem to exhibit a universal RSF as the deduced RSFs from different excitation energies show only small fluctuations provided that only excitation energies above $3$ MeV are taken into account. If transitions to well-separated low-energy levels are included, the deduced RSF may change by a factor of 2–3, which might be expected because of the involved Porter-Thomas fluctuations.

Excited states in the neutron-deficient odd-$Z$ nuclide ${}^{161}\mathrm{Ta}$ were identified for the first time using the ${}^{106}\mathrm{Cd}$(${}^{58}\mathrm{Ni}$,3$p$$\gamma$) reaction at a beam energy of 270 MeV. The $\pi h_{11/2}$ band, yrast at low spin, was observed up to $(47/2^{-})$ and a further four strongly coupled bands have been established to high spin. Quasiparticle configuration assignments for the new band structures have been made on the basis of cranked shell model calculations. This work suggests that the negative-parity $\nu (f_{7/2},h_{9/2})$ orbitals are responsible for the first rotational alignment in the $\pi h_{11/2}$ band.

Reactions that involve the direct and sudden removal of a pair of like or unlike nucleons from a fast projectile beam by a light target nucleus are considered. Specifically, we study the three two-nucleon removal channels from ${}^{12}\mathrm{C}$ that populate final states in the ${}^{10}\mathrm{Be}$, ${}^{10}\mathrm{B}$, and ${}^{10}\mathrm{C}$ reaction residues. The calculated two-nucleon removal cross sections and the residue momentum distributions are compared with available high-energy data at 250, 1050, and 2010 MeV per nucleon, i.e., data that are inclusive with respect to the bound final states of the residues. The measured $\mathit{np}$ removal cross sections only are significantly greater than the values calculated, suggesting that the reaction mechanism observes enhanced $\mathit{np}$ spatial correlations compared to those present in the shell-model wave functions.

We investigate the structure of a proto-neutron star with trapped neutrinos by using quantum hadrodynamics. Ratios of the trapped neutrinos and corresponding leptons to the baryons are usually assumed to be constant. But relevant reactions associated with the $\beta$ equilibrium could be sensitive to the given density and temperature. By adopting a phenomenological lepton density that is smeared near the surface, we calculate and discuss populations of baryons and leptons, equations of state, and the mass-radius relation of a proto-neutron star in an isentropic process.

The recently developed structure model that uses the generator coordinate method to perform configuration mixing of angular-momentum projected wave functions, generated by constrained self-consistent relativistic mean-field calculations for triaxial shapes (3DAMP$+$GCM), is applied in a systematic study of ground states and low-energy collective states in the even-even magnesium isotopes ${}^{20–40}$Mg. Results obtained using a relativistic point-coupling nucleon-nucleon effective interaction in the particle-hole channel and a density-independent $\delta$ interaction in the pairing channel are compared to data and with previous axial 1DAMP$+$GCM calculations, both with a relativistic density functional and the nonrelativistic Gogny force. The effects of the inclusion of triaxial degrees of freedom on the low-energy spectra and $E2$ transitions of magnesium isotopes are examined.

Spectroscopic calculations are carried out for the description of the shape/phase transition in Pt nuclei in terms of the interacting boson model (IBM) Hamiltonian derived from (constrained) Hartree-Fock-Bogoliubov (HFB) calculations with the finite range and density-dependent Gogny-D1S energy density functional. Assuming that the many-nucleon driven dynamics of nuclear surface deformation can be simulated by effective bosonic degrees of freedom, the Gogny-D1S potential energy surface (PES) with quadrupole degrees of freedom is mapped onto the corresponding PES of the IBM. By using this mapping procedure, the parameters of the IBM Hamiltonian, relevant to the low-lying quadrupole collective states, are derived as functions of the number of valence nucleons. Merits of both Gogny-HFB and IBM approaches are utilized so that the spectra and the wave functions in the laboratory system are calculated precisely. The experimental low-lying spectra of both ground-state and sideband levels are well reproduced. From the systematics of the calculated spectra and the reduced $E2$ transition probabilities $B$($E2$), the prolate-to-oblate shape/phase transition is shown to take place quite smoothly as a function of neutron number $N$ in the considered Pt isotopic chain, for which the $\gamma$ softness plays an essential role. All of these spectroscopic observables behave consistently with the relevant PES and the derived parameters of the IBM Hamiltonian as functions of $N$. Spectroscopic predictions are also made for those nuclei that do not have enough experimental $E2$ data.

An extension of the generalized density-dependent cluster model (GDDCM) is presented to study $\alpha$-cluster structure above doubly closed shells. In all cases, the microscopic $\alpha$-core potential is numerically constructed in the double-folding model with CDM3Y6 nucleon-nucleon interactions plus proton-proton Coulomb interactions. The properties of intraband $E2$ transitions and $\alpha$ decays are calculated by the exact solution of the Schrödinger equation with appropriate boundary conditions. It is found that the enhanced $B(E2)$ transition strengths are well reproduced without any effective charge and the calculations of $\alpha$-decay properties show good agreement with the available experimental data. This indicates that the GDDCM has universal applicability and equal validity regardless of whether the $\alpha$-cluster states are in light or heavy nuclei.

Excited states in ${}^{214}\mathrm{Po}$ have been populated using the ${}^{18}\mathrm{O}$ $+$ ${}^{208}\mathrm{Pb}$ reaction at 85-MeV beam energy and studied with the Euroball IV $\gamma$-multidetector array. The level scheme has been built up to $~2.7$-MeV excitation energy and spin $I=12\hslash$ from the triple-$\gamma$ coincidence data. Spin and parity values of most of the observed states have been assigned from the $\gamma$-angular properties. The configurations of the yrast states are discussed using results of empirical shell-model calculations and by analogy with the neighboring nuclei. The ${}^{214}\mathrm{Po}$ level scheme established in this work constitutes an important step for the determination of the effective nucleon-nucleon interactions beyond $N=126$.