TIERRAS: A package to simulate high energy cosmic ray showers underground, underwater and under-ice

In this paper we present TIERRAS, a Monte Carlo simulation program based on the well-known AIRES air shower simulations system that enables the propagation of particle cascades underground, providing a tool to study particles arriving underground from a primary cosmic ray on the atmosphere or to initiate cascades directly underground and propagate them, exiting into the atmosphere if necessary. We show several cross-checks of its results against CORSIKA, FLUKA, GEANT and ZHS simulations and we make some considerations regarding its possible use and limitations. The first results of full underground shower simulations are presented, as an example of the package capabilities.Program summaryProgram title: TIERRAS for AIRESCatalogue identifier: AEFO_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFO_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 36 489No. of bytes in distributed program, including test data, etc.: 3 261 669Distribution format: tar.gzProgramming language: Fortran 77 and CComputer: PC, Alpha, IBM, HP, Silicon Graphics and Sun workstationsOperating system: Linux, DEC Unix, AIX, SunOS, Unix System VRAM: 22 Mb bytesClassification: 1.1External routines: TIERRAS requires AIRES 2.8.4 to be installed on the system. AIRES 2.8.4 can be downloaded from http://www.fisica.unlp.edu.ar/auger/aires/eg_AiresDownload.html.Nature of problem: Simulation of high and ultra high energy underground particle showers.Solution method: Modification of the AIRES 2.8.4 code to accommodate underground conditions.Restrictions: In AIRES some processes that are not statistically significant on the atmosphere are not simulated. In particular, it does not include muon photonuclear processes. This imposes a limitation on the application of this package to a depth of 1 km of standard rock (or 2.5 km of water equivalent). Neutrinos are not tracked on the simulation, but their energy is taken into account in decays.Running time:   A TIERRAS for AIRES run of a 1020 eV1020 eV shower with statistical sampling (thinning) below 1012 eV1012 eV and 0.2 weight factor (see [1]) uses approximately 1 h of CPU time on an Intel Core 2 Quad Q6600 at 2.4 GHz. It uses only one core, so 4 simultaneous simulations can be run on this computer. Aires includes a spooling system to run several simultaneous jobs of any type.References:[1]S. Sciutto, AIRES 2.6 User Manual, http://www.fisica.unlp.edu.ar/auger/aires/.