Global digital data sets of soil type, soil texture, surface slope and other properties: Documentation of archived data tape

The file structure and coding of four soils data sets derived from the Zobler (1986) world soil file is described. The data were digitized on a one-degree square grid. They are suitable for large-area studies such as climate research with general circulation models, as well as in forestry, agriculture, soils, and hydrology. The first file is a data set of codes for soil unit, land-ice, or water, for all the one-degree square cells on Earth. The second file is a data set of codes for texture, land-ice, or water, for the same soil units. The third file is a data set of codes for slope, land-ice, or water for the same units. The fourth file is the SOILWRLD data set, containing information on soil properties of land cells of both Matthews' and Food and Agriculture Organization (FAO) sources. The fourth file reconciles land-classification differences between the two and has missing data filled in

Energy Loss of a High Charge Bunched Electron Beam in Plasma

There has been much interest in the blowout regime of plasma wakefield acceleration (PWFA), which features ultra-high fields and nonlinear plasma motion. Using an exact analysis, we examine here a fundamental limit of nonlinear PWFA excitation, by an infinitesimally short, relativistic electron beam. The beam energy loss in this case is shown to be linear in charge even for nonlinear plasma response, where a normalized, unitless charge exceeds unity. The physical basis for this effect is discussed, as are deviations from linear behavior observed in simulations with finite length beams.Comment: Submitted to Physical Review Letter

Probing Gauge String Formation in a Superconducting Phase Transition

Superconductors are the only experimentally accessible systems with spontaneously broken gauge symmetries which support topologically nontrivial defects, namely string defects. We propose two experiments whose aim is the observation of the dense network of these strings thought to arise, via the Kibble mechanism, in the course of a spontaneous symmetry breaking phase transition. We suggest ways to estimate the order of magnitude of the density of flux tubes produced in the phase transition. This may provide an experimental check for the theories of the production of topological defects in a spontaneously broken gauge theory, such as those employed in the context of the early Universe.Comment: 16 pages (Latex), 4 figures included, change in title, some minor changes, published versio

The Glueball in a Chiral Linear Sigma Model with Vector Mesons

We present a two-flavour linear sigma model with global chiral symmetry and (axial-)vector mesons as well as an additional glueball degree of freedom. We study the structure of the well-established scalar resonances f0(1370) and f0(1500): by a fit to experimentally known decay widths we find that f0(1370) is predominantly a \bar{q}q state and f0(1500) is predominantly a glueball state. The overall phenomenology of these two resonances can be well described. Other assignments for our mixed quarkonium-glueball states are also tested, but turn out to be in worse agreement with the phenomenology. As a by-product of our analysis, the gluon condensate is determined.Comment: 8 page

Numerical Study of the Lowest Energy Configurations for Global String-Antistring Pairs

We investigate the lowest energy configurations for string - antistring pairs at fixed separations by numerically minimizing the energy. We show that for separations smaller than a critical value, a region of false vacuum develops in the middle due to large gradient energy density. Consequently, well defined string - antistring pairs do not exist for such separations. We present an example of vortex - antivortex production by vacuum bubbles where this effect seems to play a dynamical role in the annihilation of the pair. We also study the dependence of the energy of an string-antistring pair on their separation and find deviations from a simple logarithmic dependence for small separations.Comment: 14 pages, in LATEX, 7 figures (not included

Topological String Defect Formation During the Chiral Phase Transition

We extend and generalize the seminal work of Brandenberger, Huang and Zhang on the formation of strings during chiral phase transitions(berger) and discuss the formation of abelian and non-abelian topological strings during such transitions in the early Universe and in the high energy heavy-ion collisions. Chiral symmetry as well as deconfinement are restored in the core of these defects. Formation of a dense network of string defects is likely to play an important role in the dynamics following the chiral phase transition. We speculate that such a network can give rise to non-azimuthal distribution of transverse energy in heavy-ion collisions.Comment: 10 pages, 4 figures, minor correction

Semiclassical Decay of Excited String States on Leading Regge Trajectories

We study the decay of hadrons based on a semiclassical string model. By including quark mass effects we find that the width to mass ratio \G/m is an increasing function of $m$, which increases most rapidly for massive quarks. This is consistent with the available data. The decay probability of hadrons on the leading Regge trajectories is computed taking the effect of the string rotation into account. The resulting decay probability is no longer uniform along the length of the string but varies in a manner that is in qualitative agreement with the available data. We argue in favour of possible experiments that would test our predictions more accurately and help open a window to the nonperturbative aspects of QCD.Comment: 15 PAGES, UR-1326, ER-40685-776, SU-4240-55

Photoinjector-generation of a flat electron beam with transverse emittance ratio of 100

The generation of a flat electron beam directly from a photoinjector is an attractive alternative to the electron damping ring as envisioned for linear colliders. It also has potential applications to light sources such as the generation of ultra-short x-ray pulses or Smith-Purcell free electron lasers. In this Letter, we report on the experimental generation of a flat-beam with a measured transverse emittance ratio of $100\pm 20.2$ for a bunch charge of $\sim 0.5$ nC; the smaller measured normalized root-mean-square emittance is $\sim 0.4$ $\mu$m and is limited by the resolution of our experimental setup. The experimental data, obtained at the Fermilab/NICADD Photoinjector Laboratory, are compared with numerical simulations and the expected scaling laws.Comment: 5 pages, 3 figure

Tunable Electron Multibunch Production in Plasma Wakefield Accelerators

Synchronized, independently tunable and focused $\mu$J-class laser pulses are used to release multiple electron populations via photo-ionization inside an electron-beam driven plasma wave. By varying the laser foci in the laboratory frame and the position of the underdense photocathodes in the co-moving frame, the delays between the produced bunches and their energies are adjusted. The resulting multibunches have ultra-high quality and brightness, allowing for hitherto impossible bunch configurations such as spatially overlapping bunch populations with strictly separated energies, which opens up a new regime for light sources such as free-electron-lasers