Cross sections for the ${}^1\mathrm{H}$($e,e^{\prime }{\pi }^{+})n$ process on ${}^1\mathrm{H}$, ${}^2\mathrm{H}$, ${}^{12}\mathrm{C}$, ${}^{27}\mathrm{Al}$, ${}^{63}\mathrm{Cu}$, and ${}^{197}\mathrm{Au}$ targets were measured at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) to extract nuclear transparencies. Data were taken from $Q^2=1.1$–4.7 GeV${}^2$ for a fixed center-of-mass energy of $W=2.14$ GeV. The ratio of ${\sigma }_L$ and ${\sigma }_T$ was extracted from the measured cross sections for ${}^1\mathrm{H}$, ${}^2\mathrm{H}$, ${}^{12}\mathrm{C}$, and ${}^{63}\mathrm{Cu}$ targets at $Q^2=2.15$ and 4.0 GeV${}^2$, allowing for additional studies of the reaction mechanism. In this article, we present the experimental setup and the analysis of the data in detail, including systematic uncertainty studies. Differential cross sections and nuclear transparencies as a function of the pion momentum at different values of $Q^2$ are presented. Our results are consistent with the predicted early onset of color transparency in mesons. Global features of the data are discussed and the data are compared with model calculations for the ${}^1\mathrm{H}$($e,e^{\prime }{\pi }^{+}$)n reaction from nuclear targets.

The pseudorapidity density of charged particles produced at collisions at energies available at the CERN Large Hadron Collider (LHC) are predicted by using two complementary production mechanisms with a set of consistent integrated and unintegrated parton distributions. We discuss the limiting fragmentation hypothesis and its possible violation, and we compare our model with other partonic models.

We study the propagation of perturbations in the quark gluon plasma. This subject has been addressed in other works and in most of the theoretical descriptions of this phenomenon the hydrodynamic equations have been linearized for simplicity. We propose an alternative approach, also based on hydrodynamics but taking into account the nonlinear terms of the equations. We show that these terms may lead to localized waves or even solitons. We use a simple equation of state for the QGP and expand the hydrodynamic equations around equilibrium configurations. The resulting differential equations describe the propagation of perturbations in the energy density. We solve them numerically and find that localized perturbations can propagate for long distances in the plasma. Under certain conditions our solutions mimic the propagation of Korteweg-de Vries solitons.

The ground-state bands of ${}^{248,250,252}\mathrm{Cf}$ have been established up to the ${10}^{+}$, ${12}^{+}$, and ${10}^{+}$ states, respectively, by in-beam $\gamma$-ray spectroscopy using neutron-transfer reactions with a $153$-MeV ${}^{18}\mathrm{O}$ beam and a highly radioactive Cf target. The deexcitation $\gamma$ rays in ${}^{248,250,252}\mathrm{Cf}$ were identified by taking coincidences with outgoing particles of ${}^{16-19}\mathrm{O}$ measured with Si $\Delta E-E$ detectors, and by selecting their kinetic energies. Moments of inertia of ${}^{248,250,252}\mathrm{Cf}$ were discussed in terms of the $N=152$ deformed shell gap.

The kaon electroproduction reaction ${}^1\mathrm{H}$($e,e^{\prime }{K}^{+}$)$\Lambda$ was studied as a function of the virtual-photon four-momentum, $Q^2$, total energy, $W$, and momentum transfer, $t$, for different values of the virtual-photon polarization parameter. Data were taken at electron beam energies ranging from $3.40$ to $5.75$ GeV. The center of mass cross section was determined for twenty-one kinematics corresponding to $Q^2$ of $1.90$ and $2.35$ GeV${}^2,$ and the longitudinal, ${\sigma }_L$, and transverse, ${\sigma }_T$, cross sections were separated using the Rosenbluth technique at fixed $W$ and $t$. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model, which better describes the observed energy dependence of ${\sigma }_T$ and ${\sigma }_L$.

Nucleon transfer reactions in low-energy deuteron-deuteron scattering are described by solving exact four-particle equations in momentum space. The Coulomb interaction between the protons is included using the screening and renormalization method. Various realistic potentials are used between nucleon pairs. The energy dependence of the differential cross section, analyzing powers, polarizations, spin-transfer coefficient, and the quintet suppression factor is studied.

We calculate the dimensionless Fermi liquid parameters (FLPs), $F_{0,1}^{\mathrm{sym}}$ and $F_{0,1}^{\mathrm{asym}}$, for spin asymmetric dense quark matter. In general, the FLPs are infrared divergent due to the exchange of massless gluons. To remove such divergences, the hard density loop (HDL) corrected gluon propagator is used. The FLPs so determined are then invoked to calculate magnetic properties such as magnetization $\langle M\rangle$ and magnetic susceptibility ${\chi }_M$ of spin polarized quark matter. Finally, we investigate the possibility of magnetic instability by studying the density dependence of $\langle M\rangle$ and ${\chi }_M$.

Using the momentum-dependent effective interaction (MDI) for nucleons, we have studied the transition density and pressure at the boundary between the inner crust and the liquid core of hot neutron stars. We find that their values are larger in neutrino-trapped neutron stars than in neutrino-free neutron stars. Furthermore, both are found to decrease with increasing temperature of a neutron star as well as increasing slope parameter of the nuclear symmetry energy, except that the transition pressure in neutrino-trapped neutron stars for the case of small symmetry energy slope parameter first increases and then decreases with increasing temperature. We have also studied the effect of the nuclear symmetry energy on the critical temperature above which the inner crust in a hot neutron star disappears and found that with increasing value of the symmetry energy slope parameter, the critical temperature decreases slightly in neutrino-trapped neutron stars but first decreases and then increases in neutrino-free neutron stars.

We use two available methods, the Duhem-Gibbs relation and the entropy formula in terms of particle phase-space distributions, to calculate the entropy in a quark combination model. The entropy of the system extracted from the Duhem-Gibbs relation is found to increase in hadronization if the average temperature of the hadronic phase is lower than that of the quark phase. The increase of the entropy can also be confirmed from the entropy formula if the volume of the hadronic phase is larger than $2.5$–$3.0$ times that of the quark phase. So whether the entropy increases or decreases during combination depends on the temperature before and after combination and on how much expansion the system undergoes during combination. The current study provides an example to shed light on the entropy issue in the quark combination model.

The dipole response of the doubly magic nuclide ${}^{208}\mathrm{Pb}$ was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 9.0 and 15.0 MeV. The present $(\gamma ,{\gamma }^{\prime })$ data combined with $(\gamma ,n)$ data from the literature are compared with results of shell-model calculations and calculations using a quasiparticle random-phase approximation. The shell-model calculations including (2p-2h) excitations describe the experimental $E1$ strength well and reproduce the spreading of the giant dipole resonance by applying a small smearing width only.

To study the energy dependence of incomplete fusion processes, the recoil range distributions for the reactions ${}^{181}\mathrm{Ta}$(${}^{16}\mathrm{O}$,xn), ${}^{181}\mathrm{Ta}$(${}^{16}\mathrm{O}$,pxn), ${}^{181}\mathrm{Ta}$(${}^{16}\mathrm{O}$,$\alpha$n), ${}^{181}\mathrm{Ta}$(${}^{16}\mathrm{O}$,$\alpha 2$n), ${}^{181}\mathrm{Ta}$(${}^{16}\mathrm{O}$,$\alpha 3$n), and ${}^{181}\mathrm{Ta}$(${}^{16}\mathrm{O}$,$2\alpha 3$n) have been measured at $\approx 81$-, 90-, and 96 MeV beam energies. The disentanglement of the complete and incomplete fusion processes have been done in terms of full and partial linear momentum transfer from the projectile to the target nucleus. The measurements have been done using recoil catcher technique. The experimentally measured forward recoil range distributions have been interpreted in terms of breakup fusion model. Detailed analysis of the data indicates that incomplete fusion processes have significant contribution at energies as low as $\approx 5$ MeV/nucleon and their contribution is found to increase with energy.

We introduce the concepts of participant triangularity and triangular flow in heavy-ion collisions, analogous to the definitions of participant eccentricity and elliptic flow. The participant triangularity characterizes the triangular anisotropy of the initial nuclear overlap geometry and arises from event-by-event fluctuations in the participant-nucleon collision points. In studies using a multiphase transport model (AMPT), a triangular flow signal is observed that is proportional to the participant triangularity and corresponds to a large third Fourier coefficient in two-particle azimuthal correlation functions. Using two-particle azimuthal correlations at large pseudorapidity separations measured by the PHOBOS and STAR experiments, we show that this Fourier component is also present in data. Ratios of the second and third Fourier coefficients in data exhibit similar trends as a function of centrality and transverse momentum as in AMPT calculations. These findings suggest a significant contribution of triangular flow to the ridge and broad away-side features observed in data. Triangular flow provides a new handle on the initial collision geometry and collective expansion dynamics in heavy-ion collisions.

High-precision measurements of superallowed $0^{+}\to 0^{+}$ $\beta$ decays of $T=2$ nuclides such as ${}^{20}\mathrm{Mg}$, ${}^{24}\mathrm{Si}$, ${}^{28}\mathrm{S}$, and ${}^{32}\mathrm{Ar}$ can contribute to searches for physics beyond the standard model of particle physics if the $Q_{\mathrm{EC}}$ values are accurate to a few keV or better. As a step toward providing precise $Q_{\mathrm{EC}}$ values for these decays, the ground-state masses of the respective daughter nuclei ${}^{20}\mathrm{Na}$, ${}^{24}\mathrm{Al}$, ${}^{28}\mathrm{P}$, and ${}^{32}\mathrm{Cl}$ have been determined by measuring the (${}^3\mathrm{He},t$) reactions leading to them with the ${}^{36}\mathrm{Ar}$(${}^3\mathrm{He},t$)${}^{36}\mathrm{K}$ reaction as a calibration. A quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph was used together with thin ion-implanted carbon-foil targets of ${}^{20}\mathrm{Ne}$, ${}^{24}\mathrm{Mg}$, ${}^{28}\mathrm{Si}$, ${}^{32}\mathrm{S}$, and ${}^{36}\mathrm{Ar}$. The masses of ${}^{20}\mathrm{Na}$ and ${}^{32}\mathrm{Cl}$ are found to be in good agreement with the values from the 2003 Atomic Mass Evaluation (AME03) [G. Audi, A. H. Wapstra, and C. Thibault, Nucl. Phys. A 729, 337 (2003)], and the precision has been improved by a factor of 6 in both cases. The masses of ${}^{24}\mathrm{Al}$ and ${}^{28}\mathrm{P}$ are found to be higher than the values from AME03 by 9.5 keV ($3.2\sigma$) and 11.5 keV ($3.6\sigma$), respectively, and the precision has been improved by a factor of 2.5 in both cases. The new ${}^{32}\mathrm{Cl}$ mass is used together with the excitation energy of its lowest $T=2$ level and the mass of ${}^{32}\mathrm{Ar}$ to derive an improved superallowed $Q_{\mathrm{EC}}$ value of 6087.3(22) keV for this case. The effects on quantities related to standard-model tests including the $\beta$-$\nu$ correlation coefficient $a$ and the isospin-symmetry-breaking correction ${\delta }_C$ are examined for the $A=32$ case.

A novel method for extracting absolute resonance strengths has been investigated. By implanting ${}^{22}\mathrm{Ne}$ ions into a thick aluminum backing and simultaneously measuring the ${}^{22}\mathrm{Ne}$$+p$ and ${}^{27}\mathrm{Al}$$+p$ reactions, the strength of the $E_r^{\mathrm{lab}}=479$ keV resonance in ${}^{22}\mathrm{Ne}$($p$,$\gamma$)${}^{23}\mathrm{Na}$ was determined to be $\omega \gamma =0.524(51)$ eV. This result has significantly reduced uncertainties compared to earlier work. Our results are important for the absolute normalizations of resonance strengths in the ${}^{22}\mathrm{Ne}$($p$,$\gamma$)${}^{23}\mathrm{Na}$ hydrogen-burning reaction and in the ${}^{22}\mathrm{Ne}$$+\alpha \hspace{0.5em}s$-process neutron-source reactions.

We propose a description of pairing properties in finite systems within the canonical and microcanonical ensembles. The approach is derived by solving the BCS and self-consistent quasiparticle random-phase approximation with the Lipkin-Nogami particle-number projection at zero temperature. The obtained eigenvalues are embedded into the canonical and microcanonical ensembles. The results obtained are found in quite good agreement with the exact solutions of the doubly-folded equidistant multilevel pairing model as well as the experimental data for ${}^{56}\mathrm{Fe}$ nucleus. The merit of the present approach resides in its simplicity and its application to a wider range of particle number, where the exact solution is impracticable.

The mass excess of the superallowed $\beta$ emitter ${}^{26}\mathrm{Si}$ has been determined with the LEBIT Penning trap mass spectrometer to be $-7140.4(2.9)$ keV, in agreement with recent measurements.

The level lifetimes have been measured for a shears band of ${}^{108}\mathrm{Cd}$ that exhibits band crossing. The observed level energies and $B(M1)$ rates have been successfully described by a semiclassical geometric model based on shear mechanism. In this geometric model, the band crossing in the shears band has been described as the reopening of the angle between the blades of a shear.

Second random-phase approximation (RPA) calculations with a Skyrme force are performed to describe both high- and low-lying excited states in ${}^{16}\mathrm{O}$. The coupling between one particle-one hole and two particle-two hole as well as that between two particle-two hole configurations among themselves are fully taken into account, and the residual interaction is never neglected; we do not resort therefore to a generally used approximate scheme where only the first kind of coupling is considered. The issue of the rearrangement terms in the matrix elements beyond the standard RPA will be considered in detail in a forthcoming paper. Two approximations are employed here for these rearrangement terms: they are either neglected or evaluated with the RPA procedure. As a general feature of second RPA results, a several-MeV shift of the strength distribution to lower energies is systematically found with respect to RPA distributions. A much more important fragmentation of the strength is also naturally provided by the second RPA owing to the huge number of two particle–two hole configurations. A better description of the excitation energies of the low-lying $0^{+}$ and $2^{+}$ states is obtained with the second RPA than with the RPA.

The stable and neutron-rich isotopes ${}^{168}\mathrm{Er}$, ${}^{170}\mathrm{Er}$, and ${}^{172}\mathrm{Er}$ have been studied with Gammasphere using inelastic excitation with energetic ${}^{136}\mathrm{Xe}$ beams. The previously assigned structures based on the proposed $K^{\pi }=4^{-}$ isomeric intrinsic states in both ${}^{168}\mathrm{Er}$ and ${}^{170}\mathrm{Er}$ have been re-evaluated and an equivalent band identified in ${}^{172}\mathrm{Er}$. In ${}^{170}\mathrm{Er}$, the identification of a $K^{\pi }=6^{-}$ band with transitions close in energy to those of the $4^{-}$ band leads to a modified interpretation, since the overlap would have compromised previous analyses. The $g_K-g_R$ values for the $4^{-}$ bands deduced from the in-band $\gamma$-ray intensities for the sequence of isotopes suggest a predominantly two-neutron configuration in ${}^{168}\mathrm{Er}$, an equally mixed two-neutron, two-proton configuration in ${}^{170}\mathrm{Er}$, and a two-proton configuration in ${}^{172}\mathrm{Er}$. A comprehensive decay scheme for the previously proposed $6^{+}$ isomer in ${}^{172}\mathrm{Er}$ has also been established, as well as band structures built on this isomer that closely resemble the $6^{+}$ and $7^{-}$ two-neutron structures known in the isotone ${}^{174}\mathrm{Yb}$. The implied $K$ hindrances are discussed. The main decay path of the $6^{+}$ isomer occurs through the newly identified $4^{-}$ isomer. The measured lifetimes of the $4^{-}$ and $6^{+}$ isomers in ${}^{172}\mathrm{Er}$ are 57(3) and 822(90) ns, respectively. Multiquasiparticle calculations support the suggested configuration changes across the isotopic chain.