my_star/StRoot/StFlowMaker/README

Maker:		StFlowMaker
Files:		StFlowMaker.cxx
		StFlowMaker.h
		StFlowEvent.cxx
		StFlowEvent.h
		StFlowTrackCollection.cxx
		StFlowTrackCollection.h
		StFlowTrack.cxx
		StFlowTrack.h
		StFlowCutEvent.cxx
		StFlowCutEvent.h
		StFlowCutTrack.cxx
		StFlowCutTrack.h
		StFlowPicoEvent.h
		StFlowPicoEvent.cxx
		StFlowSelection.h
		StFlowSelection.cxx
		StFlowConstants.h
		StFlowConstants.cxx
Authors		Raimond Snellings, Art Poskanzer, and Sergei Voloshin
		with lots of help from Glenn Cooper 
Date:		Dec 1999
Description:

** StFlowMaker: 

StFlowMaker creates StFlowEvent from StEvent or from StFlowPicoEvent
after event and track cuts. StFlowEvent contains a track collection
(StFlowTrackCollection) which contains tracks (StFlowTrack).

In Init, StFlowMaker reads the PhiWgt values for the TPCs and FTPCs from
flowPhiWgt.hist.root . These are used for making the event plane
isotropic in the lab.

In Make, it stores in StFlowEvent the PhiWgt values, the RunID, the
EventID, the CTB signal, the ZDC east and west signals, the beam
energy, the beam mass for East and West, the trigger word, the
original track multiplicities for negative and positive particles, the
multiplicity within |eta| < 0.75, the centrality bin, and the primary
vertex position. In each StFlowTrack it stores phi, global phi, eta,
global eta, p_t, global p_t, charge, dE/dx, deviant pid for each
particle, pid, dca, global dca, chi2, fit points, and max
points. StFlowTrack can also calculate total p and rapidity.

In Finish, it prints the lists of cuts and selections.

** StFlowEvent:

StFlowEvent contains member functions which return PhiWeight, Mult,
MeanPt, Q (the event plane vector), Psi (the event plane angle), and q
(=Q/sqrt(Mult)). It contains the functions which make the random
sub-events, the eta separated sub-events, and set the pid values.  It
also contains the function which sets the flags for each track saying
whether it is used in the event plane determined for each harmonic,
each selection, and each subevent. StFlowEvent is used in the flow
analysis by StFlowTagMaker and StFlowAnalysisMaker.

It now supports the StFlowCumulantMaker by calculating the generating
functions for the old and new cumulant methods, and a Q vector
normalized by the sum of the squares of the weights.

** Cut Classes:

The StFlowCutEvent and StFlowCutTrack classes have all functions and
data members static. Therefore, there is no need to instantiate. Just
use StuCutEvent::func(); or StuCutTrack::func(); . The reason for
making them static was to keep count of the number of events and
tracks removed by each cut. Call the PrintCutList functions in Finish
to print these counters.

Right now the event cuts are on centrality, multiplicity and primary
vertex position. The track cuts are on chi2, dca, pt, eta, fit points,
and the ratio of fit point to max points. These can be applied to TPC
tracks, FTPC tracks, or global tracks. It is set up so that other cuts
can be easily added. If lo >= hi on a cut, the cut is not applied.

In CheckEvent and CheckTrack the calling argument is a pointer to the
event or track.

CutTrack also stores the number of tracks with positive and negative
pseudorapidity. In CheckEvent::CheckEtaSymmetry these counters are
used to calculate (Pos - Neg) / (Pos + Neg). A cut is put on this
ratio after correcting for an acceptance effect and normalizing with
the square root of the multiplicity. The purpose is to eliminate
beam-gas background where most of the particles would go one way or
the other.

Before run 4 trigger words were used to describe the triggers. After 
run 4 multiple triggers could be satisfied by one event and a trigger
collection is used. The scheme for selecting triggers therefore changed
with the user being forced to make a choice as to which triggers to look
for.

** StFlowPicoEvent:

This is a persistent sub-set of StFlowEvent which can be written out
to disk.

** Selection Class:

The StFlowSelection class is used to select events and tracks from
StFlowEvent which have already passed the above cuts. If one calls the
Select() member function with a pointer to StFlowTrack it selects
tracks for the event plane determination which have the indicated
harmonic, selection, subevent, and PID. The SelectPart() member
function selects tracks for correlating with the event plane which
have the indicated pid, pt, total p, rapidity, eta, fit points, ratio
of fit points to max points, chi2, global dca, and dca.

** Constants:

StFlowConstants contains constants which are used in more than one file.