HERMES : a Monte Carlo program system for beam materials interaction studies

HERMES ($\underline{H}$igh $\underline{E}$nergy $\underline{R}$adiation $\underline{M}$onte Carlo $\underline{E}$laborate $\underline{S}$ystem) is a system of Monte-Carlo computer codes that are necessary to treat the different physics to be considered in computer simulation of radiation Iransport and interaction problems. In addition HERMES offers powerful capabilities of Monte-Carlo analysis and of verging the outcomes of partial programs into final results. An interfacing system - the "HERMES submission file" - provides easy interchange of input/output data between programs by standardized date structures and aliows unproblematicextension of the HERMES System by introducing new programs. The HERMES collection of physics programs permits the simulation of secondary particle histories induced by primary particles of any energy up to the regime of high-energy physics and down to thermal energies, e. g. for neutrons. The particles, that are considered by the programs of the HERMES system are p, n, $\pi^{+}$, $\pi^{-}$, $\pi^{O}$, $\pi^{\pm}$, e$^{+}$, e$^{-}$, $\gamma$, and light ions to A=10. The development of particle cascades can be simulated within very complex geometries and material configurations wich only minor restrictions. The geometry description is identical for all Monte-Carlo programs incorporated in HERMES and made in input terms of the approved "Combinatorial Geometry (CG)" in a KFA extended version. The well established programs of the HERMES System in general have been taken as original Codes as far as possible. However, to satisfy the needs of some applications, e. g., the high energy calorimeter simulation, some extensions and changes became necessary. Also the interfacing technique by HERMES submission fites needs some additional programming. Therefore, the name of the original codes were extended by a KFA suffix. All changes made to the original codes are docuvented within this report. For simplicity reasons, however, we refer to the original names throughout this document, e. g. HETC rather than HETC-KFA 2. Several of the system codes, especially for analysis purposes, are provided by the authors. To achieve portability of the HERMES system, the original coding of the programs was converted to the FORTRAN77 standard. This, however, was verified only an two computer systems, the IBM 3081 and the CRAY-KMP22

Isospin decomposition of the basic double-pionic fusion in the region of the ABC effect

Exclusive and kinematically complete high-statistics measurements of the basic double pionic fusion reactions pn -> dpi0pi0, pn -> d pi+pi- and pp -> dpi+pi0 have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the dpi0pi0 channel exhibits the ABC effect, i.e. a low-mass enhancement in the pipi-invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the dpi+pi0 channel shows a smooth behavior consistent with the conventional t-channel Delta Delta process. The dpi+pi- data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account