eff.C basically take 2 pt distributions and take their ratio and fit a 
function to it.

before one runs eff.C, the 2 histograms have to be created using xyz.C. 
these 2 histograms are pt distributions of embedded and reconstructed 
tracks.

eff.C has to be run in a separate directory from hist.C and fits.C

...

detailed procedure (this is the same as procedure.txt in eff/ dir)
1. edit y0templateeff.lsf
        - set up cuts
        - select the data files (pi-, K-, pbar)
2. source yalleff.scr
        - this will run xyz.C and create 2 pt distributions (embedded and
reconstructed tracks)
        - inside fits/, 2 directories will be created, e.g. fits/pi/ and fits/pia
3. edit eff.lsf
        - change the keyword, (the same one used in step 2)
        - change particle type, (ditto)
4. source eff.lsf
        - this calls eff.C, which will takes the ratio of the two pt histograms and
fit it with a function
        - it will create .txt file inside au20/ containing 3 parameters: a, b, and
c. later on, corryield.C will looks for these 3 parameters and apply them to the raw
invariant yields
-------------------------

rp
feb-03