Date post: | 21-Dec-2015 |
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Who am I?
PhD Student from the University of Melbourne, working on ATLAS
Will be in Krakow for 4 months Working on transition of HEPTOOLS
to HepMC
What is HEPEVT? What is HepMC? Event Records for Monte Carlo Generators Makes the interfacing of different event
generators simpler However, there will always be ambiguities
and limitations to the way the event information is stored.
HEPEVENT is the Fortran HEP standard HepMC is a C++ container
Event contains a list of vertices
Vertices have pointers to their incoming and outgoing particles
Spin density matrices can be stored
+ Flow information (such as colour)
Motivation to move to HepMC High Energy Particle Physics tools are
becoming Object Orientated Frameworks for running MC-generators
E.g. Athena (ATLAS software) is written in C++ and python
Monte-Carlo Generators E.g. Pythia 8, Hergwig++
HepMC is becoming a standard container for event records
Step One: MC-tester
Gain experience using HepMC Demonstrates general event record
interface for HEPEVT and HepMC Great testing tool for checking new
C++ Monte-Carlo generators against their older Fortran version.
What is MC-TESTER?
Written by Piotr Golonka, Tomasz Pierzchala, Zbigniew Was.
C++ Program from around 2003 Automates the comparison of intermediate
state decays for different Monte-Carlo generators.
Produces a list comparing branching ratios and invariant mass distributions for the decay modes found.
Table of decay Table of decay modes:modes:
●Decay channel
●Branching ratio for generator #1 and #2
●Rough statistical errors of branching ratios
●Maximal “Shape Difference Parameter”
●Similarity Coefficients(combined: for all decay modes)Slide from one of Piotr’s Talk!
●Histogrammes of invariant mass from generator
#1 and #2
●Ratio of the two histogrammes
●Shape Difference Parameter value
Example of histogrammes:Example of histogrammes:
Slide from one of Piotr’s Talk!
Two classes added
HepMCEvent (Inherits from the HepEvent and HepMC::GenEvent classes) Has a list of HepMCParticles Implemented some basic method to access these
HepMCParticle (Inherits from the HepParticle and HepMC::GenParticle classes) Implemented methods to access GenParticle
properties Also methods to getList of Mother/Daughter
Particles is needed by MC-Tester Other methods left as stub as not needed by MC-
tester
C++ example added
Example of use in main method for the pythia 8 event generatior
… //Initialize MC-TESTER MC_Initialize();… + Some configuration
In event loop { … // Fill phythia event // to HepMC format ToHepMC.fill_next_event( event, HepMCEvt );
//Make new MC-TESTER // HepMCEvent event and // pass to the tester HepMCEvent * temp_event = new HepMCEvent(*HepMCEvt); MC_Analyze(temp_event);}
//Finalise MC-TESTER MC_Finalize();…
Example: Comparision of pythia 6.4 (Fortran) to pythia 8.1 (C++) Is now possible to compare the output
of Fortran and C++ monte-carlo generators.
Example: tau decay in e+eZ0 events