Momentum spectrum of hadronic secondaries in the multiperipheral model

Journal ArticleMotivated by a simplified multiperipheral model, we formulate a general qualitative description of the momentum spectrum of secondaries, resulting from a collision of two hadrons at high energies. Arguing from two fundamental multiperipheral concepts, (a) that transverse momenta are limited and (b) that distant particles on the multiperipheral chain are uncorrelated, we predict that at sufficiently high incident energies, the momentum spectrum of particle X in the reaction a ± b → X + anything, when presented in the variables pi and y = sinh-1[pll(pi2±mx2)½], develops a central plateau in the y dependence, which elongates and flattens to a value that is normalized b y the total cross section as the incident energy increases. Moreover, it is shown that the resultant particle density distribution is consistent with the hypothesis of limiting fragmentation. We contrast this description with the predictions of the two-fireball model, the isobar-pionization model, and the statistical thermodynamical model

Quark-bag model with low-energy pion interactions. I. Theory

Journal ArticleA standard method for restoring chiral symmetry in the bag model is to introduce an explicit external pion field. Questions of the consistency and compatibility of this method with the assumptions of the static-cavity approximation of the bag model are discussed. An approximate version of the model is justified. It is argued that consistency requires treating pion-induced quark-pair creation and annihilation at the bag surface as a zeroth-order process in pion-coupling perturbation theory. An approximation treating these pairs as an inward extension of the pion field is discussed. The resulting model gives an improved value of gA

Hadronic deformation energy. II. Two-nucleon interaction

Journal ArticleThe MIT bag model for hadrons is treated in the static cavity approximation. The adiabatic deformation of a six-quark hadron with quantum numbers of the deuteron is studied in a configuration which permits the separation of two triplets with quantum numbers of the neutron and proton. The energy of the system is computed to second order in the gluon coupling and presented as a function of two choices of a single collective variable: a separation parameter for the nucleons and the baryonic quadrupole moment. The present study considers only interactions at short and intermediate range in a state with nuclear spins aligned in parallel along the deformation axis. It does not treat effects depending on nucleon momenta. The energy, when expressed in terms of a nuclear separation parameter, exhibits a soft repulsive core at short range due to a color-magnetic gluon interaction, and strong attraction in intermediate range due to a color-electric interaction

Pseudodeconfinement and dynamical confinement in the quark plasma

Journal ArticleWe elaborate upon phenomenological models of high-temperature hadronic matter at zero baryon density. We discuss the choice of a practical set of "fundamental" degrees of freedom, indicate their relationship to dynamically confined plasma modes, and suggest in what way they may account for the phase transition and other thermodynamic features. We offer a partial resolution to the conflict between the requirement of dynamical confinement and the apparent thermodynamic deconfinement of the plasma. When all quark masses are large, the quarks may appear to be deconfined, even though they are technically confined

Quark Gluon Plasma from Numerical Simulations of Lattice QCD

Numerical simulations of quantum chromodynamics at nonzero temperature provide information from first principles about the physical properties of the quark gluon plasma. Because the lattice approximation can be refined indefinitely, results of lattice simulations now provide the most reliable basis for our understanding of the nonperturbative characteristics of the plasma and of the high temperature phase transition. Following a brief overview of the methodology of lattice gauge theory at nonzero temperature, recent results and insights from lattice simulations are discussed. These include our understanding of the phase diagram of QCD, the nature of the phase transition, and the structure of the plasma.Comment: Review article to appear in Quark Gluon Plasma 2, edited by R. Hwa, World Scientific, 1995. 50 pp in one Postscript file, gz-compressed, uuencode