Disclaimer:
this is only an example to get going! Remember that OSCAR and ORCA are
works in progress! We want to demonstrate how to work within the CMS
environment setup on the UAF farm at FNAL. All examples were created
and tested on Redhat 7 based systems (don't forget the
PROC_RESOURCES=RH7 statement in the jdf file) and will not!! work on
the RedHat 6 systems. We will use some simple physics analysis to
demonstrate how:
- Monte-Carlo events are generated and stored
(CMKIN)
- The CMS detector is described and its interaction with particles are
simulated (OSCAR)
- Simulated events are digitized (ORCA)
- To create DST's starting from the digitized events
In addition we will
learn how to:
- Setup the CMS
software environment here at Fermilab
- Use the farm for a small MC production
- Generate a MC sample, convert the ntuple with h2root into a root
file,...
- Use root to make a few plots on generator level
- Run the generated events through OSCAR the GEANT4 base detector
simulation.
- Run the digitization step using ORCA
- Run some ntuple makers on the ORCA output
- Do some simple analysis
Click the
links below to start the exercise. The physics analysis we
will use is a Z' with a mass of 700 GeV that we force to decay into 2
muons. (This actually might be one of the first discoveries at the
LHC). The scope here is to learn about the computing environment and to
do a very simple analysis. In this exercise we don't mix in pile
up (yet)!
Be aware that you
have to do the exercise in sequence! (with the exception of the
last bullet which can be executed without whenever)
1. General setup
2. Available data sets
in DST format
3. Event generation on the
farm with CMKIN (Pythia), Analysis of the generator level output.
4. Simulate the events with
OSCAR.
5. Digitize with ORCA and
produce DST's
6. Run a muon ROOT Tree
maker looking at the DST and make some simple plots
The figure below
shows the simple and robust processing model we will use in all the
examples involving the farm to process events in parallel. When the
process starts all the input data is staged in from Mass Storage.
Then all the
libraries are loaded and all necessary database constants
(geometry ...) are read in. During the processing the nodes are
completely independent all the output is to local disk. In the end the
results are stored in Mass storage. This is very robust all nodes
are completely independent. In case a process fails we just have to
resubmit that process.
For Tutorials
concerning CMKIN and the CMS OO software have a look at the Tutotials
given at CERN :
The Tutorial main
page: http://cmsdoc.cern.ch/cms/software/tutorials/
Absolute beginner: http://cmsdoc.cern.ch/orca/Tutorials/20031114-CERN/NewUser/
Full analysis chain: http://cmsdoc.cern.ch/orca/Tutorials/20031128-CERN/FullChain/Contents.html
COBRA: http://cobra.web.cern.ch/cobra/Tutorial743/index.html
Tracking: http://cmsdoc.cern.ch/orca/Tutorials/20040109-CERN/index.html
Other good web pages to find information are:
http://cobra.web.cern.ch/cobra/Tutorial743/index.html
http://cmsdoc.cern.ch/cmsoo/cmsoo.html
