• access to reconstructed events information
• environment for physics analysis code developments
• tool for mDST processing and filtering of events' sub-samples

Where to find it

Documentation

• Classes
• FAQ (From-time-to-time Asked Questions)
• Release notes
• ./INSTALL and ./coral/README files (it is inside PHAST distributive)

Where to install

How to install

• tar xzvf Phast.tar.gz.x.yyy
• cd phast.x.yyy

If (by chance :-) you have correct environment, then PHAST could be compiled simply by typing

• make

Where to find mDST data

• mDST files of our "official" data production could be found on CASTOR :
  /castor/cern.ch/compass/data/YYYY/oracle_dst/PPP/mDST/
  where YYYY is data taking year and PPP is data taking period.

How to produce mDST

If you want to produce mDST yourself (for example if you need mDST with additional detector hits information), see ./coral/README for instruction how to link PHAST with CORAL, how to activate mDST output and how to control mDST content.
(Where to find CORAL, how to build it, how to run it see on CORAL web page).

How to analyze

Most simple way of analysis is just reading of existing mDST by PHAST and filling histograms with physics values you want to study. You can do it inside so called "user function(s)".

In the same time (inside "user function") one may also create a simple NTUPLE (10-20-30 variables) for interactive analysis in ROOT ('a la PAW').

Reading of mDSTs could be done recursively many times, i.e. at each iteration you may read mDST and write an output microDST with events selected by your algorithm(s). Such microDSTs could be read in again for further event selection etc. etc.

How to do it you may find in examples of user's code:

• ./user/UserEvent0.cc (K0 event selection, K*(892) search)
• ./user/UserEvent1.cc (access to mu+N -> mu'+X reconstructed events kinematics)
Those examples are good "starting point" for newcomers.

The only place user suppose to work with is ./user/ directory (and maybe ./fortran/ for Fortraners)
Main user's "working place" is UserEventN() function(s) (N=0,1,2...) (i.e. files ./user/UserEventN.cc).
For every N there is really 3 user's functions:

• UserEventN() will be called every event.
• UserRunEndN() function will be called every time run number is changing in the input event stream.
• UserJobEndN() will be called at very end of job.
If you need some of them, just create corresponding file(s) (e.g. UserEvent12.cc) in ./user/ directory.

Which set of user functions will be called is controlled by -uN option. Multiple "-u" options are allowed. If more then one "-u" was specified, user functions will be called one after another in the arithmetic order.

All *.h , *.cc files in ./user/ directory will be compiled automatically, than put to shared library and linked to executable by means of "make" command executed in top PHAST directory. For users' ROOT derived classes ROOT dictionary will be created and compiled automatically.
./user/Makefile* should never be modified by user.
If PHAST has to be compiled on a platform different from default one (lxplus.cern.ch), user has to reset symbolic link Makefile in PHAST top directory to Makefile.your_platform

Example of how to start PHAST with UserEvent0 (filtering out of events with K0 candidate):
./phast -u0 -o events_with_K0.root path-to-mDST-directory/mDST*.root

Some defaults:

• histogram file name is 'hist.root' (could be changed by -h option)
• Output (microDST) is off (use '-o out_file' option to switch it on)
• No "user" packages is called (use -uN option(s) to change it)

Input file(s) (as well as output file and histograms) could be CASTOR files (if CASTOR is accessible from your machine). But in this case wildcards in file names are not supported (it's a property of CASTOR itself).
In this case one may create text file with file names you want to process (e.g. files.txt) and give it to PHAST input by -l option. For example:
./phast -l files.txt -u0 -o out.root

To get help on PHAST options, type
./phast
(without arguments)

To force normal termination of PHAST job before it ends itself, just send HUP signal to process:
kill -HUP pid
or type once CTRL-C if you are running interactively.

How to access reconstructed event information and setup related information.

Easiest way to learn it is to start working with provided examples.

Description of classes and functions for data access could be found in HTML documentation generated out of PHAST code comments. PDF version is also available.
It's advisable to look first into PaEvent class documentation as it's top class in the event data hierarchy and to PaSetup as top class for geometry description and other event-independent information.

There are also other (less recommended) ways to access mDST data.

22.07.2011 S.Gerassimov