The role of nuclear reactions in Monte Carlo calculations of absorbed and biological effective dose distributions in hadron therapy

Monte Carlo codes are rapidly spreading among hadron therapy community due to their sophisticated nuclear/electromagnetic models which allow an improved description of the complex mixed radiation field produced by nuclear reactions in therapeutic irradiation. In this contribution results obtained with the Monte Carlo code FLUKA are presented focusing on the production of secondary fragments in carbon ion interaction with water and on CT-based calculations of absorbed and biological effective dose for typical clinical situations. The results of the simulations are compared with the available experimental data and with the predictions of the GSI analytical treatment planning code TRiP

Ground-state Spectrum of Light-quark Mesons

A confining, Goldstone theorem preserving, separable Ansatz for the ladder kernel of the two-body Bethe-Salpeter equation is constructed from phenomenologically efficacious $u$, $d$ and $s$ dressed-quark propagators. The simplicity of the approach is its merit. It provides a good description of the ground-state isovector-pseudoscalar, vector and axial-vector meson spectrum; facilitates an exploration of the relative importance of various components of the two-body Bethe-Salpeter amplitudes, showing that sub-leading Dirac components are quantitatively important in the isovector-pseudoscalar meson channels; and allows a scrutiny of the domain of applicability of ladder truncation studies. A colour-antitriplet diquark spectrum is obtained. Shortcomings of separable Ans\"atze and the ladder kernel are highlighted.Comment: 30 pages, LaTeX/REVTEX 3.0, no figure

Isospin Multiplet Structure in Ultra--Heavy Fermion Bound States

The coupled Bethe--Salpeter bound state equations for a $Q\bar Q$ system, where $Q=(U,D)$ is a degenerate, fourth generation, super--heavy quark doublet, are solved in several ladder approximation models. The exchanges of gluon, Higgs and Goldstone modes in the standard model are calculated in the ultra--heavy quark limit where weak $\gamma, W^\pm$ and $Z^0$ contributions are negligible. A natural $I=0$ and $I=1$ multiplet pattern is found, with large splittings occuring between the different weak iso--spin states when $M_Q$, the quark masses, are larger than values in the range $0.4 TeV<M_Q<0.8 TeV$, depending on which model is used. Consideration of ultra--heavy quark lifetime constraints and $U-D$ mass splitting constraints are reviewed to establish the plausibility of lifetime and mass degeneracy requirements assumed for this paper.Comment: 20 pages, 7 figures (hard copy available upon request), report# KU-HEP-93-2

Computerized Scanning Auger Microprobe

An Auger spectrometer has been automated using a microcomputer. Fundamental considerations in the design and choice of the computerized system are presented and should be of general interest. The spectrometer was a Physical Electronics Ind. model 545 scanning Auger microprobe. The microcomputer chosen was a Southwest Technical Products 6809 computer system. Hardware details are discussed with emphasis on the four computer-spectrometer interface boards. These boards are (1) Auger energy control board, which sets the Auger detection energy with its 16 bit digital-to-analog converter (DAC); (2) read Auger signal board, which reads the Auger signal intensity with its 12 bit analog-to-digital converter; (3) multipurpose DAC board, which uses two pairs of 8 bit DAC\u27s to position the excitation beam and display the data in memory on a CRT monitor, and (4) timing and relay control board, which selects various instruments and power supplies as required during the fully automated depth profiling sputter sequences. Organizational details of the control, analysis, and output software are discussed. The operation of the main Auger control program is emphasized along with its menu driven options, which provide great versatility to the operator. Examples are shown of the various data output modes, which include displays on the CRT monitor and plots from the multicolor digital plotter. © 1985, American Vacuum Society. All rights reserved

Turbulence and passive scalar transport in a free-slip surface

We consider the two-dimensional (2D) flow in a flat free-slip surface that bounds a three-dimensional (3D) volume in which the flow is turbulent. The equations of motion for the two-dimensional flow in the surface are neither compressible nor incompressible but strongly influenced by the 3D flow underneath the surface. The velocity correlation functions in the 2D surface and in the 3D volume scale with the same exponents. In the viscous subrange the amplitudes are the same, but in the inertial subrange the 2D one is reduced to 2/3 of the 3D amplitude. The surface flow is more strongly intermittent than the 3D volume flow. Geometric scaling theory is used to derive a relation between the scaling of the velocity field and the density fluctuations of a passive scalar advected on the surface.Comment: 11 pages, 10 Postscript figure

Decay constants, semi-leptonic and non-leptonic decays in a Bethe-Salpeter Model

We evaluate the decay constants for the B and $D$ mesons and the form factors for the semileptonic decays of the B meson to $D$ and $D^*$ mesons in a Bethe-Salpeter model. From data we extract $V_{cb}=0.039 \pm 0.002$ from ${\bar B} \to D^* l {\bar{\nu}}$ and $V_{cb}=0.037 \pm 0.004$ from ${\bar B} \to D l {\bar{\nu}}$ decays. The form factors are then used to obtain non-leptonic decay partial widths for $B\to D \pi (K)$ and $B \to D D (D_s)$ in the factorization approximation.Comment: 15 Pages, 3 Postscript figures (available also from [email protected]

Turbulence in a free surface

We report an experimental and numerical study of turbulent fluid motion in a free surface. The flow is realized experimentally on the surface of a tank filled with water stirred by a vertically oscillating grid positioned well below the surface. Particles floating on the surface are used to visualize the flow. The effect of surface waves appears to be negligible. The flow is unconventional in that it is confined to two dimensions but does not have squared vorticity as a conservation law, that it is not divergence free and that it inherits scaling features of the mean square velocity differences S_2(R) and the vorticity fluctuations Omega(R) from the bulk 3-d turbulence.Comment: 4 pages, 4 Postscript figure

Relativistic Calculation of the Meson Spectrum: a Fully Covariant Treatment Versus Standard Treatments

A large number of treatments of the meson spectrum have been tried that consider mesons as quark - anti quark bound states. Recently, we used relativistic quantum "constraint" mechanics to introduce a fully covariant treatment defined by two coupled Dirac equations. For field-theoretic interactions, this procedure functions as a "quantum mechanical transform of Bethe-Salpeter equation". Here, we test its spectral fits against those provided by an assortment of models: Wisconsin model, Iowa State model, Brayshaw model, and the popular semi-relativistic treatment of Godfrey and Isgur. We find that the fit provided by the two-body Dirac model for the entire meson spectrum competes with the best fits to partial spectra provided by the others and does so with the smallest number of interaction functions without additional cutoff parameters necessary to make other approaches numerically tractable. We discuss the distinguishing features of our model that may account for the relative overall success of its fits. Note especially that in our approach for QCD, the resulting pion mass and associated Goldstone behavior depend sensitively on the preservation of relativistic couplings that are crucial for its success when solved nonperturbatively for the analogous two-body bound-states of QED.Comment: 75 pages, 6 figures, revised content