Recent experimental data appear to confirm the existence of the exotic ${\Theta }^{+}\left(uudd\overline{s}\right)$ baryon. Simple statistical considerations, which have generally proven rather successful, suggest that this particle should be produced in observable abundance in relativistic nuclear collisions at RHIC, where it may be identified through the ${\mathrm{pK}}_s^0$ invariant mass spectrum. The observation would not only add new evidence for its existence, but would also provide an additional means for probing the collision system, especially with regard to strangeness.

The polarized longitudinal-transverse structure function ${\sigma }_{{\mathrm{LT}}^{\prime }}$ has been measured in the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonance region at $Q^2=0.40\mathrm{}$ and $0.65{\mathrm{GeV}}^2.$ Data for the $p\left(\overrightarrow{e}{,e}^{\prime }p\right){\pi }^0$ reaction were taken at Jefferson Lab with the CEBAF large acceptance spectrometer (CLAS) using longitudinally polarized electrons at an energy of 1.515 GeV. For the first time a complete angular distribution was measured, permitting the separation of different nonresonant amplitudes using a partial wave analysis. Comparison with previous beam asymmetry measurements at MAMI indicate a deviation from the predicted $Q^2$ dependence of ${\sigma }_{{\mathrm{LT}}^{\prime }}$ using recent phenomenological models.

The level structure of ${}^{229}\mathrm{Th},$ produced by α-particle decay of ${}^{233}\mathrm{U},$ was studied with γ-ray spectroscopy measurements. The sources were continuously separated from daughters with ion-exchange chromatographic methods. Singles and coincidence measurements were performed with high-purity germanium detectors. Energies and intensities of about 220 $\gamma$ rays were accurately determined. About 70 transitions were reported for the first time, especially in the 300–700 keV energy range. A ${}^{229}\mathrm{Th}$ level scheme was proposed, accounting for 220 transitions among 47 excited states. Alpha-particle feeding intensities and hindrance factors were deduced and compared to direct α-particle measurements; the agreement was found to be relatively good. The level structure was interpreted in the framework of rotational and/or reflection asymmetric models. The agreement with experimental data was shown to be satisfactory.

Proton emission from the odd-odd nuclei ${}^{146}\mathrm{Tm}$ and ${}^{150}\mathrm{Lu}$ has been reinvestigated by means of the recoil mass spectrometer. In the ${}^{146}\mathrm{Tm}$ study, the strongest proton transitions at 1.12 MeV and at 1.19 MeV have been assigned to the decay of ${}^{146m}\mathrm{Tm}$ ${(T}_{1/2}=200\mathrm{}\pm 10\mathrm{ms})$ and to the ${}^{146gs}\mathrm{Tm}$ decay ${(T}_{1/2}=80\mathrm{}\pm 10\mathrm{ms}),$ respectively. Three new proton lines were identified at 0.89 MeV, 0.94 MeV, and 1.01 MeV. The observed decay pattern has been interpreted by using spherical estimates of emission probabilities. The decays of ${}^{146m,gs}\mathrm{Tm}$ to the $\nu s_{1/2}$ ${}^{145}\mathrm{Er}$ ground state and to excited neutron states originating from the $\nu h_{11/2}$ orbital are reported. This work represents the first observation of fine structure in proton emission from an odd-odd nucleus. In the ${}^{150}\mathrm{Lu}$ study, the proton energy and half-life values of $E_p=1277\mathrm{}\pm 8\mathrm{keV}$ and $T_{1/2}{=39\mathrm{}}_{-6}^{+8\mathrm{}}\mu \mathrm{s}$ for the decay of ${}^{150m}\mathrm{Lu}$ were obtained with better precision, but no evidence for fine structure in the proton emission was found.

Using a relativistic effective Lagrangian at the hadronic level, near-threshold $\omega$- and $\phi$-meson productions in proton-proton $\mathrm{}\left(\mathrm{pp}\right)\mathrm{}$ collisions, $p\overrightarrow{p}\mathrm{pp}\omega /\phi ,$ are studied within the distorted wave Born approximation. Both initial and final state $\mathrm{pp}$ interactions are included. In addition to total cross section data, both $\omega$ and $\phi$ angular distribution data are used to constrain further the model parameters. For the $p\overrightarrow{p}\mathrm{pp}\omega$ reaction, we consider two different possibilities: with and without the inclusion of nucleon resonances. The nucleon resonances are included in a way to be consistent with the ${\pi }^{-}\overrightarrow{p}\omega n$ reaction. It is shown that the inclusion of nucleon resonances can describe the data better overall than without their inclusion. However, the SATURNE data in the range of excess energies $Q<\mathrm{}31\mathrm{}$ MeV are still underestimated by about a factor of 2. As for the $p\overrightarrow{p}\mathrm{pp}\phi$ reaction, it is found that the presently limited available data from DISTO can be reproduced by four sets of values for the vector and tensor $\phi \mathrm{NN}$ coupling constants. Further measurements of the energy dependence of the total cross section near threshold energies should help to constrain better the $\phi \mathrm{NN}$ coupling constant.

Fission lifetime studies are performed using the “neutron-clock” technique associated with statistical and dynamical model calculations. In this framework we have undertaken, at the Louvain-la-Neuve cyclotron facility, the study of ${}^{20}\mathrm{Ne}{+}^{159}\mathrm{Tb}$ and ${}^{20}\mathrm{Ne}{+}^{169}\mathrm{Tm}$ induced fission reactions between $E/A=8\mathrm{}$ and 16 MeV. In this work we have determined (a) fusion-evaporation and fusion-fission cross sections; (b) the prescission and postscission multiplicities of evaporated light particle (neutron, proton, and alpha) and their energy and angular distributions, and (c) the total energy balance of fission process after taking into account preequilibrium or incomplete-fusion processes. The comparison of the experimental data, multiplicities, and cross sections, with the statistical-model calculations incorporating simple aspects of the dynamics have enabled us to determine the ranges of fission lifetimes and the contribution of fast fission at different compound-nucleus excitation energies.

We present an analysis of the reaction ${}^8\mathrm{Li}{+}^{208}\mathrm{Pb},$ which has been recently measured at energies around the Coulomb barrier. The study is focused on the elastic and one-neutron removal channels. The elastic angular distribution has been analyzed by means of the optical model and coupled-channels method. The measured ${}^7\mathrm{Li}$ yield has been assumed to come from the one-neutron transfer reaction ${}^{208}\mathrm{Pb}{(}^8\mathrm{Li},$ ${}^7\mathrm{Li}{)}^{209}\mathrm{Pb}$ and the breakup reaction ${}^8\mathrm{Li}{+}^{208}\mathrm{Pb}\to {n+}^7\mathrm{Li}{+}^{208}\mathrm{Pb}.$ For the former, an analysis in terms of the distorted wave Born approximation and coupled-channels Born approximation (CCBA) methods has been performed. For the breakup reaction, a generalization of the CCBA method has been used, in which the final states are described as ${n+}^{208}\mathrm{Pb}$ continuum states. Transfer and breakup are then treated consistently. The summed angular distribution for the two processes reproduces the shape and absolute magnitude of the measured ${}^7\mathrm{Li}$ distribution. We conclude that most of the measured ${}^7\mathrm{Li}$ yield comes from the one-neutron transfer channel. We also show that the elastic scattering is notably affected by the strong coupling to transfer channels.

The color dielectric modification of the gluon dispersion relation in a dense QCD medium suppresses both the soft and collinear gluon radiation associated with jet production. We compute the longitudinal and transverse plasmon contributions to the zeroth order in opacity radiative energy loss in the one-loop hard thermal loop approximation. This is QCD analog of the Ter-Mikayelian effect in QED and leads to $\sim 30\%$ reduction of the energy loss of high transverse momentum charm quarks produced in a QCD plasma with a characteristic Debye mass $\mu \sim 0.5\mathrm{GeV}.$

We calculate total hadron-hadron cross sections at high energies using the Low-Nussinov two-gluon model of the Pomeron. The gluon exchange is represented by a phenomenological potential including screened color-Coulomb, screened confining, and spin-spin interactions. We use bound-state wave functions obtained from a potential model for mesons, and a Gaussian wave function for a proton. We evaluate total cross sections for collisions involving $\pi ,$ K, $\rho ,$ $\phi ,$ D, $J/\psi ,$ ${\psi }^{\prime },$ ${\rm Y},$ ${{\rm Y}}^{\prime },$ and the proton. We find that the total cross sections increase with the square of the sum of the root-mean-square radii of the colliding hadrons, but there are variations arising from the spin-spin interaction. We also calculate the total cross sections of a mixed-color charmonium state on a pion and on a proton. The dependence of the total cross section on the size and the color state of the charmonium is investigated.

In this paper an equation of state of neutron star matter, which includes strange baryons in the framework of Zimanyi and Moszkowski model has been obtained. We focus on the effects of the isospin dependence of the equation of state and construct the hyperon star model for the fitted parameters. Numerous neutron star models show that the appearance of hyperons is connected with the increasing density in neutron star interiors. Analysis carried out in this paper shows that the inclusion of $\delta$ meson and additional nonlinear meson interaction terms affects the density dependence of the symmetry energy and the chemical composition of a neutron star. Since the effective baryon masses contribute to baryon chemical potentials, they also alter the chemical composition of the star. The obtained model of the star not only excludes large population of hyperons but also does not significantly reduce the lepton content in the star interior.

Structure of cold nuclear matter at subnuclear densities for the proton fraction $x=0.5,$ 0.3, and 0.1 is investigated by quantum molecular dynamics (QMD) simulations. We demonstrate that the phases with slablike and rodlike nuclei, etc. can be formed dynamically from hot uniform nuclear matter without any assumptions on nuclear shape, and also systematically analyze the structure of cold matter using two-point correlation functions and Minkowski functionals. In our simulations, we also observe intermediate phases, which have complicated nuclear shapes. It has been found out that these phases can be characterized as those with negative Euler characteristic. Our result implies the existence of these kinds of phases in addition to the simple “pasta” phases in neutron star crusts and supernova inner cores. In addition, we investigate the properties of the effective QMD interaction used in the present work to examine the validity of our results. The resultant energy per nucleon ${\epsilon }_n$ of the pure neutron matter, the proton chemical ${\mu }_p^{\mathrm{}\left(0\right)\mathrm{}}$ in pure neutron matter and the nuclear surface tension $E_{\mathrm{surf}}$ are generally reasonable in comparison with other nuclear interactions.

Nuclear medium effects in the neutrino cooling of neutron stars through the reaction channel $\gamma \overrightarrow{\gamma }{\pi }^0\to {\nu }_R{\overline{\nu }}_L\left({\nu }_L{\overline{\nu }}_R\right)$ are incorporated. Throughout the paper we discuss different possibilities of right-handed neutrinos, massive left-handed neutrinos, and standard massless left-handed neutrinos (reaction is then allowed only with medium modified vertices). It is demonstrated that multiparticle effects suppress the rate of this reaction channel in the dense hadron matter by 6–7 orders of magnitude that does not allow to decrease existing experimental upper limit on the corresponding ${\pi }^0\nu \overline{\nu }$ coupling. Other possibilities of the manifestation of the given reaction channel in different physical situations, e.g., in the quark color superconducting cores of the most massive neutron stars, are also discussed. We demonstrate that in the color-flavor-locked superconducting phase for temperatures $T\lesssim 0.1–10\mathrm{MeV}$ (depending on the effective pion mass and the decay width) the process is feasibly the most efficient neutrino cooling process, although the absolute value of the reaction rate is rather small.

A thermodynamic model for multifragmentation which is frequently used appears to give very different values for specific heat at constant volume depending upon whether canonical or grand canonical ensemble is used. The cause for this discrepancy is analyzed.

Mean lifetimes of five levels in the S band and three levels in the ground-state band of ${}^{156}\mathrm{Dy},$ populated via the ${}^{124}\mathrm{Sn}{(}^{36}\mathrm{S},4n)$ reaction at $E=145\mathrm{}\mathrm{MeV},$ were measured by the Doppler-shift attenuation technique using a line-shape analysis. The differential decay-curve method was applied for a lifetime determination. In contrast with earlier data, the present $B\left(E2\mathrm{}\right)\mathrm{}$ values in the yrast band do not indicate a reduction in the collectivity after the crossing between the S band and the ground-state band, and confirm the results of theoretical calculations using mean-field approaches.

Here we calculate the first correction to the thermal distribution function of an expanding gas due to shear viscosity. With this modified distribution function we estimate viscous corrections to spectra, elliptic flow, and Hanbury Brown–Twiss (HBT) radii in hydrodynamic simulations of heavy ion collisions using the blast wave model. For reasonable values of the shear viscosity, viscous corrections become of the order of 1 when the transverse momentum of the particle is larger than 1.7 GeV. This places a bound on the $p_T$ range accessible to hydrodynamics for this observable. Shear corrections to elliptic flow cause $v_2{(p}_T)$ to veer below the ideal results for $p_T\approx 0.9\mathrm{GeV}.$ Shear corrections to the longitudinal HBT radius $R_L^2$ are large and negative. The reduction of $R_L^2$ can be traced to the reduction of the longitudinal pressure. Viscous corrections cause the longitudinal radius to deviate from the $1/\sqrt{m_T}$ scaling which is observed in the data and which is predicted by ideal hydrodynamics. The correction to the sideward radius $R_S^2$ is small. The correction to the outward radius $R_O^2$ is also negative and tends to make $R_O{/R}_S\approx 1.$

We identify conditions under which a summation over nucleon resonances can yield, via quark-hadron duality, parton model results for electromagnetic and neutrino structure functions at large x. While a summation over the lowest even and odd parity multiplets is sufficient to achieve duality in the symmetric quark model, a suppression of transitions to specific final states is required for more realistic cases incorporating SU(6) breaking. We outline several scenarios consistent with duality, discuss their implications for the high $Q^2$ behavior of transition form factors, and illustrate how they can expose the patterns in the flavor-spin dependence of interquark forces.

We investigate the properties of mixed stars formed by hadronic and quark matter in $\beta$ equilibrium described by appropriate equations of state (EOS) in the framework of relativistic mean-field theory. We use the nonlinear Walecka model for the hadron matter and the MIT Bag and the Nambu-Jona-Lasinio (NJL) models for the quark matter. The phase transition to a deconfined quark phase is investigated. In particular, we study the dependence of the onset of a mixed phase and a pure quark phase on the hyperon couplings, quark model, and properties of the hadronic model. We calculate the strangeness fraction with baryonic density for the different EOS. With the NJL model the strangeness content in the mixed phase decreases. The calculations were performed for $T=0\mathrm{}$ and for finite temperatures in order to describe neutron and proto-neutron stars. The star properties are discussed. Both the Bag model and the NJL model predict a mixed phase in the interior of the star. Maximum allowed masses for proto-neutron stars are larger for the NJL model $\left(\sim {1.9M}_{\odot }\right)$ than that for the Bag model $\left(\sim {1.6M}_{\odot }\right).\mathrm{}$

We systematically analyze the recent claim that nonrelativistic and relativistic mean field (RMF) based random phase approximation (RPA) calculations for the centroid energy $E_0$ of the isoscalar giant monopole resonance yield for the nuclear matter incompressibility coefficient $K_{\mathrm{nm}}$ values which differ by about $20\%.$ For an appropriate comparison with the RMF based RPA calculations, we obtain the parameters of the Skyrme force used in the nonrelativistic model by adopting the same procedure as employed in the determination of the NL3 parameter set of the effective Lagrangian used in the RMF model. Our investigation suggests that the discrepancy between the values of $K_{\mathrm{nm}}$ predicted by the relativistic and nonrelativistic models is significantly less than $20\%.$

Higher order Fourier coefficients of the azimuthally dependent single particle spectra resulting from noncentral heavy ion collisions are investigated. For intermediate to large transverse momenta, these anisotropies are expected to become as large as 5%, and should be clearly measurable. The physics content of these observables is discussed from two different extreme but complementary viewpoints, hydrodynamics and the geometric limit with extreme energy loss.

TRIUMF experiment 497 has measured the parity-violating longitudinal analyzing power $A_z$ in $\overrightarrow{p}p$ elastic scattering at 221.3 MeV incident proton energy. This comprehensive paper includes details of the corrections, some of magnitude comparable to $A_z$ itself, required to arrive at the final result. The largest correction was for the effects of first moments of transverse polarization. The addition of the result, $A_z=[0.84\pm 0.29(\mathrm{stat}.\mathrm{})\pm 0.17(\mathrm{syst}.\mathrm{}\left)\right]\times {10}^{-7},$ to the $\overrightarrow{p}p$ parity-violation experimental data base greatly improves the experimental constraints on the weak meson-nucleon coupling constants $h_{\rho }^{\mathrm{pp}}$ and $h_{\omega }^{\mathrm{pp}},$ and also has implications for the interpretation of electron parity-violation experiments.