June 11, 2002, updated June 25
2nd method (Dan) to get centrality at 20 GeV
See
a)
all_raw.gif
b)
all_norm.gif
c)
au130+au200.gif
d)
au20+au200.gif
The abcisa factors in the figures for au130 and au200 are shown.
One observes good consistency in the scaling from au200 and au130.
The results shown in the above figures seem consistent with the method
used earlier at 20 GeV suggested by Zhangbu. Updated results of this
method, including 20, 130 and 200 GeV are presented
here
This
Fig.
shows the good agreement observed at 20, 130 and 200 GeV. The
points at 0% cross section were obtained using Zhangbu's method. All the
points above 0% for 130 and 200 GeV were determined previously at STAR.
The points above 0% cross section for 20 GeV were obtained using the 2nd
method discussed here.
Here are details of what was done on the 2nd method suggested by
Dan Cebra:
0) Files :
au20:
/auto/stardata/starspec3/flow_pDST_production/reco/minBias22GeVZDC/ReversedHalfField/P02ge/2001/
au130: /auto/stardata/starspec/schweda/pDST/P01hi/minbias/global/
au200:
/auto/stardata/starspec2/flow_pDST_production/reco/MinBiasVertex/ReversedFullField/P01gk/2001/
1) It was verified independently that mUncorrNegMult and mUncorrPosMult
indeed correspond do the number of tracks as defined in Masashi's code
that produces pDst. See Masashi's e-mail to Roppon:
------------------------------------------------------------------
mUncorrNegMult and mUncorrPosMult are copied from StEventUtilities
function uncorrectedNumberOfNegativePrimaries(const StEvent&) and
uncorrectedNumberOfPositivePrimaries(cont StEvent&).
It is number of tracks that are:
number of Fit points >=10
|eta|<=0.5
DCA < 3.0 cm
For detail, please look at $STAR/StRoot/StEventUtilities/StuRefMult.hh.
mMultEta seems to be defined as number of tracks of which |eta|<0.75.
It is counted by a variable goodTracksEta in StFlowMaker.cxx in SL02e.
I used SL02e to produced 20GeV Au+Au flow pico DSTs, because it is
P02ge production.
Best regards,
Masashi Kaneta
------------------------------------------------------------------------
2) Histograms were made for Nch= mUncorrNegMult+mUncorrPosMult, as defined
in the code. x-bin= 800. Printed out the x and y values.
3) In a spread sheet program (Kaleid) the x-axis for au130
was multiplied by a factor x130 such that the spectra along the x-axis
matches (by eye) the one for au20. Also the y-axis of the au130
spectra was scaled to match (by eye) the spectra at au20.
Similarly, the x-axis for au200 was multiplied by a factor x200 such
that the spectra along the x-axis
matches (by eye) the one for au20. Also the y-axis of the au200
spectra was scaled to match (by eye) the spectra at au20.
The present factors x130 and x200 extracted are listed
in the figures and here:
au130: x130=0.652
au200: x200=0.562
4) Finally, the centrality values for au20 derived from those
determined for au130, as quoted by Manuel, are listed next. The last
column was
obtained by multiplying the au130 values
by x130 = 0.652, as determined above.
cent au130 au20
-------------------
05% 431.00 281
10% 364.00 237
20% 260.00 170
30% 179.00 117
40% 118.00 76
50% 74.000 48
60% 43.000 28
70% 22.000 14
80% 10.000 7