Flash of photons from the early stage of heavy-ion collisions

The dynamics of partonic cascades may be an important aspect for particle production in relativistic collisions of nuclei at CERN SPS and BNL RHIC energies. Within the Parton-Cascade Model, we estimate the production of single photons from such cascades due to scattering of quarks and gluons q g -> q gamma, quark-antiquark annihilation q qbar -> g gamma, or gamma gamma, and from electromagnetic brems-strahlung of quarks q -> q gamma. We find that the latter QED branching process plays the dominant role for photon production, similarly as the QCD branchings q -> q g and g -> g g play a crucial role for parton multiplication. We conclude therefore that photons accompanying the parton cascade evolution during the early stage of heavy-ion collisions shed light on the formation of a partonic plasma.Comment: 4 pages including 3 postscript figure

Closed classes of functions, generalized constraints and clusters

Classes of functions of several variables on arbitrary non-empty domains that are closed under permutation of variables and addition of dummy variables are characterized in terms of generalized constraints, and hereby Hellerstein's Galois theory of functions and generalized constraints is extended to infinite domains. Furthermore, classes of operations on arbitrary non-empty domains that are closed under permutation of variables, addition of dummy variables and composition are characterized in terms of clusters, and a Galois connection is established between operations and clusters.Comment: 21 page

Analysis of reaction dynamics at RHIC in a combined parton/hadron transport approach

We introduce a transport approach which combines partonic and hadronic degrees of freedom on an equal footing and discuss the resulting reaction dynamics. The initial parton dynamics is modeled in the framework of the parton cascade model, hadronization is performed via a cluster hadronization model and configuration space coalescence, and the hadronic phase is described by a microscopic hadronic transport approach. The resulting reaction dynamics indicates a strong influence of hadronic rescattering on the space-time pattern of hadronic freeze-out and on the shape of transverse mass spectra. Freeze-out times and transverse radii increase by factors of 2 - 3 depending on the hadron species.Comment: 10 pages, 4 eps figures include

Imprint of Gravitational Lensing by Population III Stars in Gamma Ray Burst Light Curves

We propose a novel method to extract the imprint of gravitational lensing by Pop III stars in the light curves of Gamma Ray Bursts (GRBs). Significant portions of GRBs can originate in hypernovae of Pop III stars and be gravitationally lensed by foreground Pop III stars or their remnants. If the lens mass is on the order of $10^2-10^3M_\odot$ and the lens redshift is greater than 10, the time delay between two lensed images of a GRB is $\approx 1$s and the image separation is $\approx 10 \mu$as. Although it is difficult to resolve the two lensed images spatially with current facilities, the light curves of two images are superimposed with a delay of $\approx 1$ s. GRB light curves usually exhibit noticeable variability, where each spike is less than 1s. If a GRB is lensed, all spikes are superimposed with the same time delay. Hence, if the autocorrelation of light curve with changing time interval is calculated, it should show the resonance at the time delay of lensed images. Applying this autocorrelation method to GRB light curves which are archived as the {\it BATSE} catalogue, we demonstrate that more than half light curves can show the recognizable resonance, if they are lensed. Furthermore, in 1821 GRBs we actually find one candidate of GRB lensed by a Pop III star, which may be located at redshift 20-200. The present method is quite straightforward and therefore provides an effective tool to search for Pop III stars at redshift greater than 10. Using this method, we may find more candidates of GRBs lensed by Pop III stars in the data by the {\it Swift} satellite.Comment: 13 pages, 13 figures, accepted for publication in Ap

Space, Time and Color in Hadron Production Via e+e- -> Z0 and e+e- -> W+W-

The time-evolution of jets in hadronic e+e- events at LEP is investigated in both position- and momentum-space, with emphasis on effects due to color flow and particle correlations. We address dynamical aspects of the four simultanously-evolving, cross-talking parton cascades that appear in the reaction e+e- -> gamma/Z0 -> W+W- -> q1 q~2 q3 q~4, and compare with the familiar two-parton cascades in e+e- -> Z0 -> q1 q~2. We use a QCD statistical transport approach, in which the multiparticle final state is treated as an evolving mixture of partons and hadrons, whose proportions are controlled by their local space-time geography via standard perturbative QCD parton shower evolution and a phenomenological model for non-perturbative parton-cluster formation followed by cluster decays into hadrons. Our numerical simulations exhibit a characteristic `inside-outside' evolution simultanously in position and momentum space. We compare three different model treatments of color flow, and find large effects due to cluster formation by the combination of partons from different W parents. In particular, we find in our preferred model a shift of several hundred MeV in the apparent mass of the W, which is considerably larger than in previous model calculations. This suggests that the determination of the W mass at LEP2 may turn out to be a sensitive probe of spatial correlations and hadronization dynamics.Comment: 52 pages, latex, 18 figures as uu-encoded postscript fil

Analysis of location uncertainty for a microearthquake cluster: A case study

In many reservoirs, an increase in permeability and conductivity is achieved by hydraulic fracturing/stimulations which open cracks and fractures that then act as pathways for fluids to navigate in the subsurface. Mapping, localization, and general characterization of these fracture systems is of key importance in oil, gas, and geothermal energy production. The location of the microseismic events triggered during hydraulic fracturing or stimulation can help to characterize the properties of the fracture system. There are many different methods for localizing microearthquakes and, in general, these methods yield different locations, velocity models, and event origin times, due to differences in algorithms and input models. Here we focus on studying location confidence intervals associated with two localization methods, classical (triangulation) and Double-Difference, where uncertainties due to origin times can be marginalized away, thus decreasing uncertainties in the event locations. We relocate events using these two methods and three different velocity models. Of the two methods used here, Double-Difference produces smallest confidence regions. We also illustrate that, for our dataset in particular, marginalizing away the influence of the unknown origin times also improves the confidence intervals

Isoscalar-isovector mass splittings in excited mesons

Mass splittings between the isovector and isoscalar members of meson nonets arise in part from hadronic loop diagrams which violate the Okubo-Zweig-Iizuka rule. Using a model for these loop processes which works qualitatively well in the established nonets, I tabulate predictions for the splittings and associated isoscalar mixing angles in the remaining nonets below about 2.5 GeV, and explain some of their systematic features. The results for excited vector mesons compare favorably with experiment.Comment: 8 RevTeX pages, including 1 LaTeX figure. CMU-HEP93-23/DOE-ER-40682-4

Deep-Inelastic Final States in a Space-Time Description of Shower Development and Hadronization

We extend a quantum kinetic approach to the description of hadronic showers in space, time and momentum space to deep-inelastic $ep$ collisions, with particular reference to experiments at HERA. We follow the history of hard scattering events back to the initial hadronic state and forward to the formation of colour-singlet pre-hadronic clusters and their decays into hadrons. The time evolution of the space-like initial-state shower and the time-like secondary partons are treated similarly, and cluster formation is treated using a spatial criterion motivated by confinement and a non-perturbative model for hadronization. We calculate the time evolution of particle distributions in rapidity, transverse and longitudinal space. We also compare the transverse hadronic energy flow and the distribution of observed hadronic masses with experimental data from HERA, and find encouraging results. The techniques developed in this paper may be applied in the future to more complicated processes such as eA, pp, pA and AA collisions.Comment: 44 pages plus 14 postscript figure

Validation of gyrokinetic modelling of light impurity transport including rotation in ASDEX Upgrade

Upgraded spectroscopic hardware and an improved impurity concentration calculation allow accurate determination of boron density in the ASDEX Upgrade tokamak. A database of boron measurements is compared to quasilinear and nonlinear gyrokinetic simulations including Coriolis and centrifugal rotational effects over a range of H-mode plasma regimes. The peaking of the measured boron profiles shows a strong anti-correlation with the plasma rotation gradient, via a relationship explained and reproduced by the theory. It is demonstrated that the rotodiffusive impurity flux driven by the rotation gradient is required for the modelling to reproduce the hollow boron profiles at higher rotation gradients. The nonlinear simulations validate the quasilinear approach, and, with the addition of perpendicular flow shear, demonstrate that each symmetry breaking mechanism that causes momentum transport also couples to rotodiffusion. At lower rotation gradients, the parallel compressive convection is required to match the most peaked boron profiles. The sensitivities of both datasets to possible errors is investigated, and quantitative agreement is found within the estimated uncertainties. The approach used can be considered a template for mitigating uncertainty in quantitative comparisons between simulation and experiment.Comment: 19 pages, 11 figures, accepted in Nuclear Fusio