Universal interface of TAUOLA: Technical and physics documentation

Abstract

Because of their narrow width, τ decays can be well separated from their production process. Only spin degrees of freedom connect these two parts of the physics process of interest for high energy collision experiments. In the following, we present a Monte Carlo algorithm which is based on that property. The interface supplements events generated by other programs, with τ decays. Effects of spin, including transverse degrees of freedom, genuine weak corrections or of new physics may be taken into account at the time when a τ decay is generated and written into an event record. The physics content of the C++ interface is already now richer than its FORTRAN predecessor. Program summary Program title: TAUOLA++, versions 1.0.2, 1.0.3, 1.0.4, 1.0.5, 1.0.6 Catalogue identifier: AELH_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AELH_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 649 068 No. of bytes in distributed program, including test data, etc.: 6 544 479 Distribution format: tar.gz Programming language: C++, FORTRAN77 Computer: PCs, workstations Operating system: Linux, MacOS RAM: < 10 MB Classification: 11.2 External routines: HepMC ( http://lcgapp.cern.ch/project/simu/HepMC/), optional; PYTHIA8 ( http://home.thep.lu.se/~torbjorn/Pythia.html) Subprograms used: Cat Id Title Reference ADSM_v2_0 MC-TESTER Comput. Phys. Commun. 182 (2011) 779 Nature of problem: The code of Monte Carlo generators often has to be tuned to the needs of large HEP Collaborations and experiments. In particular τ lepton decays need to be added (or modified) to the previously generated (or measured) events encapsulated in an event record. Solution method: The new algorithm, the universal interface of TAUOLA which works with the HepMC event record of C++ applications is documented. It uses the τ decay generator as described in [2] with the updates explained in [1]. For the new interface spin treatment was improved. For example it features complete spin effects in processes mediated by Z / γ ⁎ interactions. The effects of electroweak corrections can be taken into account in this case as well. In general, the program superseeds its FORTRAN predecessor [1]. The event record analysis as well as initialization is also modernized. Restrictions: The input event record must meet the requirements described in Section 2.3.1 of the documentation. Unusual features: Two sets of installation scripts; an additional tool for calculating tables for electroweak corrections. Running time: Depends on the size and complexity of the events. Small events (<50 particles), require 1 to 7 minutes for processing 1 M events on PC/Linux with a 2.4 GHz processor.