We argue that multiparticle production in high energy hadron and nuclear collisions can be considered as proceeding through the production of gluons in the background classical field. In this approach we derive the gluon spectrum immediately after the collision and find that at high energies it is parametrically enhanced by $\text{ln}(1/x)$ with respect to the quasiclassical result ($x$ is the Bjorken variable). We show that the produced gluon spectrum becomes thermal (in three dimensions) with an effective temperature determined by the saturation momentum $Q_s,T=c{Q}_s/2\pi$ during the time $\sim 1/T$; we estimate $c=\sqrt{2\pi }/2\simeq 1.2$. Although this result by itself does not imply that the gluon spectrum will remain thermal at later times, it has an interesting applications to heavy ion collisions. In particular, we discuss the possibility of Bose-Einstein condensation of the produced gluon pairs and estimate the viscosity of the produced gluon system.

The excitation spectra of nuclei in the regions $150<A<190$ and $220<A<250$ are commonly considered as showing characteristics of the rotational motion. In the present work, however, there is evidence indicating that the nuclei can evolve from rotation to vibration. We have used two simple models to discuss the collective motions of a nucleus for different spin ranges. In addition, in order to get the insight into the rotational-like properties of nuclei, as an example, shape calculations using the total Routhian surfaces (TRS) model have been carried out for positive-parity states in ${}^{156}\mathrm{Gd}$. Also we have shown the result of the nucleus ${}^{102}\mathrm{Ru}$ which is given as an example of the reverse transition, i.e., vibration to rotation. The TRS plots reveal that, with increasing spin, the former nucleus becomes slightly soft in $\gamma$ and $\beta$ deformations, while the latter one becomes rigid in the $\gamma$ deformation.

We systematically analyze total reaction cross sections of carbon isotopes with $N=$ 6–16 on a ${}^{12}\mathrm{C}$ target for wide range of incident energy. The intrinsic structure of the carbon isotope is described by a Slater determinant generated from a phenomenological mean-field potential, which reasonably well reproduces the ground-state properties for most of the even $N$ isotopes. We need separate studies not only for odd nuclei but also for ${}^{16}\mathrm{C}$ and ${}^{22}\mathrm{C}$ to improve their wave functions. The density of the carbon isotope is constructed by eliminating the effect of the center-of-mass motion. For the calculations of the cross sections, we take two schemes, the Glauber approximation and the eikonal model using a global optical potential. Both the reaction models successfully reproduce low and high incident energy data on the cross sections of ${}^{12}\mathrm{C}$, ${}^{13}\mathrm{C}$, and ${}^{16}\mathrm{C}$ on ${}^{12}\mathrm{C}$. The calculated reaction cross sections of ${}^{15}\mathrm{C}$ are found to be considerably smaller than the empirical values observed at low energy. We find a consistent parametrization of the nucleon-nucleon scattering amplitude, differently from previous ones. Finally, we predict the total reaction cross section of ${}^{22}\mathrm{C}$ on ${}^{12}\mathrm{C}$.

A precise fusion excitation function has been measured for the ${}^{12}\mathrm{C}$+${}^{208}\mathrm{Pb}$ reaction at energies around the barrier, allowing the fusion barrier distribution to be extracted. The fusion cross sections at high energies differ significantly from existing fusion data. Coupled reaction channels calculations have been carried out with the code FRESCO. A bare potential previously claimed to uniquely describe a wide range of ${}^{12}\mathrm{C}$+${}^{208}\mathrm{Pb}$ near-barrier reaction channels failed to reproduce the new fusion data. The nuclear potential diffuseness of 0.95 fm which fits the fusion excitation function over a broad energy range fails to reproduce the elastic scattering. A diffuseness of 0.55 fm reproduces the fusion barrier distribution and elastic scattering data, but significantly overpredicts the fusion cross sections at high energies. This may be due to physical processes not included in the calculations. To constrain calculations, it is desirable to have precisely measured fusion cross sections, especially at energies around the barrier.

In the frame of a phenomenological approach based on Compton-like Feynman amplitudes, we study the annihilation channel in antiproton nucleon collisions with production of a single charged or neutral pion and a lepton-antilepton pair. These reactions allow us to access nucleon and axial electromagnetic form factors in the time-like region and offer a unique possibility to study the kinematical region below the two-nucleon threshold. The differential cross section in an experimental setup where the pion is fully detected is given with explicit dependence on the relevant nucleon form factors. The possibility of measuring a heavy charged pion in the annihilation channel is also discussed.

A complete classification of $\mathit{qq}\overline{q}\overline{q}$ tetraquark states in terms of the spin-flavor, color, and spatial degrees of freedom was constructed. The permutation symmetry properties of both the spin-flavor and orbital parts of the $\mathit{qq}$ and $\overline{q}\overline{q}$ subsystems are discussed. This complete classification is general and model independent and it is useful both for model builders and experimentalists. The total wave functions are also explicitly constructed in the hypothesis of ideal mixing; this basis for tetraquark states will enable the eigenvalue problem to be solved for a definite dynamical model. An evaluation of the tetraquark spectrum was obtained from the Iachello mass formula for normal mesons, here generalized to tetraquark systems. This mass formula is a generalization of the Gell-Mann Okubo mass formula, whose coefficients have been upgraded by a study of the latest PDG data. The ground-state tetraquark nonet was identified with $f_0(600),\kappa (800),f_0(980),a_0(980)$. The diquark-antidiquark limit was also studied.

We study the properties of cold asymmetric nuclear matter at high density, applying the quark meson coupling model with excluded volume corrections in the framework of the Landau theory of relativistic Fermi liquids. We discuss the role of the finite spatial extension of composite baryons on dynamical and statistical properties such as the Landau parameters, the compressibility, and the symmetry energy. We have also calculated the low-lying collective eigenfrequencies arising from the collisionless quasiparticle transport equation, considering both unstable and stable modes. An overall analysis of the excluded volume correlations on the collective properties is performed.

We use the Glauber-Gribov multiple scattering formalism and the theory of leading-twist nuclear shadowing to develop a method for the calculation of leading-twist hard coherent diffraction in hadron-nucleus processes. We demonstrate that soft multiple rescatterings lead to the factorization breaking of hard diffraction in proton-nucleus scattering, which is larger than that in hadron-nucleon scattering. For the kinematics encountered at the CERN Large Hadron Collider (LHC) and at the BNL Relativistic Heavy Ion Collider (RHIC), we compare the hard diffr-active to electromagnetic (e.m.) mechanisms of hard coherent production of two jets in proton-nucleus scattering. We study the $x_{IP},\beta ,$ and $A$ dependence of the ratio of the dijet production cross sections due to the two effects, $R$, at the LHC and RHIC kinematics. We demonstrate that in proton-heavy nucleus hard coherent diffraction at the LHC, $R$ is small, which offers a clean method to study hard photon-proton scattering at energies exceeding those available at the DESY Hadron Electron Ring Accelerator (HERA) by a factor of ten. In contrast, the use of lighter nuclei, such as ${}^{40}\mathrm{Ca}$, allows the study of the screened nuclear diffractive parton distribution. Moreover, a comparison of the dijet diffractive production to the heavy-quark-jet diffractive production will estimate the scree-ned nuclear diffractive gluon PDF, which will be measured in nucleus-nucleus ultraperipheral collisions at the LHC.

A significant improvement has been made in the identification of $\gamma$ rays from muon capture in I, Au, and Bi, all monisotopic elements. The (${\mu }^{-},\nu n$) reaction was clearly observed in all nuclei, but the levels excited do not correlate well with the spectroscopic factors from the ($d,{}^3\mathrm{He}$) reaction. Some (${\mu }^{-},\nu 2n$), (${\mu }^{-},\nu 3n$), (${\mu }^{-},\nu 4n$), (${\mu }^{-},\nu 5n$) and other reactions have been observed at a lower yield. The muonic x-ray cascades have also been studied in detail.

In this paper, we calculate some properties of polarized neutron matter using the lowest order constrained variational method with the ${\mathrm{AV}}_{18}$ potential and employing a microscopic point of view. A comparison is also made between our results and those of other many-body techniques.

We show that the conditions which originate the spin and pseudospin symmetries in the Dirac equation are the same that produce equivalent energy spectra of relativistic spin-1/2 and spin-0 particles in the presence of vector and scalar potentials. The conclusions do not depend on the particular shapes of the potentials and can be important in different fields of physics. When both scalar and vector potentials are spherical, these conditions for isospectrality imply that the spin-orbit and Darwin terms of either the upper component or the lower component of the Dirac spinor vanish, making it equivalent, as far as energy is concerned, to a spin-0 state. In this case, besides energy, a scalar particle will also have the same orbital angular momentum as the (conserved) orbital angular momentum of either the upper or lower component of the corresponding spin-1/2 particle. We point out a few possible applications of this result.

We have calculated fusion cross sections for 64 heavy-ion systems based on a method that takes into account the couplings to a complete set of states for surface vibrations of the nuclear densities. For the nuclear interaction we have assumed the parameter-free São Paulo potential. The predictions have been obtained without using any adjustable parameter, and are in good agreement with the experimental results for most of the systems, even at sub-barrier energies.

High-spin states in ${}^{164}\mathrm{Lu}$ were populated in the ${}^{121}\mathrm{Sb}$(${}^{48}\mathrm{Ca}$,$5n$) reaction at 215 MeV and γ-ray coincidences were measured with the Gammasphere spectrometer. Through this experiment the eight known triaxial superdeformed bands in ${}^{164}\mathrm{Lu}$ could be confirmed. Some of these bands were extended to higher as well as to lower spins. Evidence is reported for the first time for weak $\Delta I=1,E1$ transitions linking TSD3 and TSD1. This observation may imply coupling to octupole vibrational degrees of freedom. The decay mechanism is different from the one observed in the neighboring even-$N$ isotopes, which exhibit wobbling excitations built on the $\pi i_{13/2}$ structure with $E2(M1),\Delta I=1$ interband decay. An additional sequence decaying at high spin into TSD1 was observed up to $I^{\pi }=({50}^{-})$. This band has a constant dynamic moment of inertia of ∼$70\hslash {}^2{\mathrm{MeV}}^{-1}$ and an alignment that is $\text{∼}2\hslash$ larger than that found for TSD1. A revision of the assumed spin-parity-assignment of TSD2 is based on the observed decay-out to normal-deformed structures. The parity and signature quantum numbers of TSD2 are now firmly assigned as $(\pi ,\alpha )=(+,0)$, in disagreement with the former assignment of $(\pi ,\alpha )=(-,1)$, which was based on the assumption that TSD2 is the signature partner of TSD1. TSD1 and TSD2 show an alignment gain at $\hslash \omega \text{∼}0.67$ and 0.60 MeV, respectively. In TSD1 the involvement of the $j_{15/2}$ neutron orbital is suggested to be responsible for the high-frequency crossing.

A particle rotor model (PRM) with a quasi-proton and a quasi-neutron coupled with a triaxial rotor is developed and applied to study chiral doublet bands with configurations of an $h_{11/2}$ proton and an $h_{11/2}$ quasi-neutron. With pairing treated by the BCS approximation, the present quasiparticle PRM is aimed at simulating one proton and many neutron holes coupled with a triaxial rotor. After a detailed analysis of the angular momentum orientations, energy separation between the partner bands, and behavior of electromagnetic transitions, for the first time we find aplanar rotation or equivalently chiral geometry beyond the usual one proton and one neutron hole coupled with a triaxial rotor.

Fission fragments of 1 GeV/nucleon ${}^{238}\mathrm{U}$ nuclei interacting with a deuterium target have been investigated with the Fragment Separator at GSI (Darmstadt) by measuring the isotopic production cross sections and fragment velocities. The combination of these two observables enabled to disentangle the high- and low-energy fission modes. Specific properties of these two modes were analyzed; in particular, the charge distribution of the fissioning projectile-like prefragments could be determined for the first time.

The thermal and phase properties of a multifragmentation model that uses clusters as degrees of freedom are explored as a function of isospin. Good qualitative agreement is found with the phase diagram of asymmetric nuclear matter as established by different mean-field models. In particular, from the convexity properties of the nuclear entropy, we show that uncharged finite nuclei display first- and second-order liquid-gas-like phase transitions. Different quantities are examined to connect the thermal properties of the system to cluster observables. In particular, we show that fractionation is only a loose indication of phase coexistence. A simple analytical formula is proposed and tested to evaluate the symmetry (free) energy from the widths of isotopic distributions. Assuming that one may restore the isotopic composition of breakup fragments, it is found that some selected isotopic observables can allow one to quantitatively access the freeze-out symmetry energy in multifragmentation experiments.

Excitations in ${}^{94}\mathrm{Ru}$ were populated through the ${\beta }^{+}/\epsilon$ decay of ${}^{94}\mathrm{Rh}$ following the fusion evaporation reaction ${}^{58}\mathrm{Ni}$(${}^{40}\mathrm{Ca}$,$3\mathit{pn}$)${}^{94}\mathrm{Rh}$. Recoiling nuclei were implanted on the Yale moving tape collector at the Wright Nuclear Structure Laboratory, and delayed γ-rays were observed via an array of four Compton suppressed HPGe clover detectors. Nine new γ-transitions and five new levels were added to the level scheme of $(\pi 1g_{\frac{9}{2}}){}_{J^{\pi }=6^{+}}^4$ level, in close agreement with prediction.

We discuss the systematics of the $2^{+}$ excitation energy and the transition probability from this $2^{+}$ to the ground state for most of the even-even nuclei, from ${}^{16}\mathrm{O}$ up to the actinides, for which data are available. To that aim we calculate their correlated $J=0$ ground state and $J=2$ first excited state by means of the angular-momentum and particle-number projected generator coordinate method, using the axial mass quadrupole moment as the generator coordinate and self-consistent mean-field states only restricted by axial, parity, and time-reversal symmetries. The calculation, which is an extension of a previous systematic calculation of correlations in the ground state, is performed within the framework of a nonrelativistic self-consistent mean-field model using the same Skyrme interaction SLy4 and a density-dependent pairing force to generate the mean-field configurations and mix them. To separate the effects due to angular-momentum projection and those related to configuration mixing, the comparison with the experimental data is performed for the full calculation and also by taking a single configuration for each angular momentum, chosen to minimize the projected energy. The theoretical energies span more than 2 orders of magnitude, ranging below 100 keV in deformed actinide nuclei to a few MeV in doubly-magic nuclei. Both approaches systematically overpredict the experiment excitation energy, by an average factor of about 1.5. The dispersion around the average is significantly better in the configuration mixing approach compared to the single-configuration results, showing the improvement brought by the inclusion of a dispersion on the quadrupole moment in the collective wave function. Both methods do much better for the quadrupole properties; using the configuration mixing approach the mean error on the experimental $B(E2)$ values is only 50%. We discuss possible improvements of the theory that could be made by introducing other constraining fields.

The spallation residues produced in the bombardment of ${}^{56}\mathrm{Fe}$ at $1.5A,1.0A,0.75A,0.5A$, and $0.3A$ GeV on a liquid-hydrogen target have been measured using the reverse kinematics technique and the fragment separator at GSI (Darmstadt). This technique has permitted the full identification in charge and mass of all isotopes produced with cross sections larger than ${10}^{-2}$ mb down to $Z=8$. Their individual production cross sections and recoil velocities at the five energies are presented. Production cross sections are compared with previously existing data and with empirical parametric formulas, often used in cosmic-ray astrophysics. The experimental data are also extensively compared with the results of different combinations of intranuclear cascade and deexcitation models. It is shown that the yields of the lightest isotopes cannot be accounted for by standard evaporation models. The GEMINI model, which includes an asymmetric fission decay mode, gives an overall good agreement with the data. These experimental data can be directly used for the estimation of composition modifications and damages in materials containing iron in spallation sources. They are also useful for improving high-precision cosmic-ray measurements.

An effective-Lagrangian framework for $K\Sigma$ photoproduction from the proton is presented. The proposed model is applicable at forward kaon angles and photon lab energies from threshold up to 16 GeV. The high-energy part of the $p(\gamma ,K^{+}){\Sigma }^0$ and $p(\gamma ,K^0){\Sigma }^{+}$ amplitudes is expressed in terms of Regge-trajectory exchange in the $t$ channel. By supplementing this Regge background with a number of $s$-channel resonances, the model is extended toward the resonance region. The resulting “Regge-plus-resonance” (RPR) approach has the advantage that the background contributions involve only a few parameters, which can be largely constrained by the high-energy data. This work compares various implementations of the RPR model, and explores which resonance contributions are required to fit the data presently at hand. It is demonstrated that, through the inclusion of one $K$ and two $K^{*}$ trajectories, the RPR framework provides an efficient and unified description of the $K^{+}{\Sigma }^0$ and $K^0{\Sigma }^{+}$ photoproduction channels over an extensive energy range.