20avril

The SSD Tracking Parameters

The number of hits taken into account in primaries tracks was very small so I change a tracking parameter (chi2) to see if there are some changes. I don't know if a chi2 = 50 is realistic but there are some changes.
Moreover, the chi2 of the calculated at each node (chi2 of the tracks) doesn't change a lot.


Figure 1 : ratio (ssd hits/primaries) for ssd chi2 = 5	Figure 2 : ratio (ssd hits/primaries) for ssd chi2 = 50


Figure 3 : chi2 of the tracks for ssd chi2 = 5	Figure 4 : chi2 of the tracks ssd chi2 = 50

One other interesting thing is to plot the ratio vs the primary vertex Z position : we clearly see in the 2 cases that the more the primary vertex is close to 0, the more SSD hits are added to the tracks.


Figure 5 : chi2 of the tracks for ssd chi2 = 5	Figure 6 : chi2 of the tracks ssd chi2 = 50

The other thing is to do this ratio but for all the SSD hits reconstructed : as you can see, there is almost the same number of primary tacks than hits that are independenly reconstruct in the SSD.


Figure 7 : chi2 of the tracks for ssd chi2 = 5	Figure 8 : chi2 of the tracks ssd chi2 = 50

However, in these 2 cases, the ratio doesn't depend on the position of the primary vertex.


Figure 9 : chi2 of the tracks for ssd chi2 = 5	Figure 10 : chi2 of the tracks ssd chi2 = 50

So finally, the chi2 is set up to chi2 = 30


Figure 11 : ratio vs z vertex	Figure 12 : ratio vs the number of primaries

Method (for me)
At each event :

count the number of primaries tracks
Loop over all the primary tracks and count those which contains a ssd hit (there is a loop over all the nodes for each track)

Another study

The file used are :
* ITTF only TPT tracking, SVT hits, no tracking for SSD
/star/data13/reco/cu62productionMinBias/FullField/DEV_ssd.nosvt/2005/073

I'm sure in this case that no tracking is done with the svt and the ssd
So the 2 cases I rerun on are with (options in the bfc Chain):

tpcI -SvtIt -SsdIt : no SVT no SSD hits used in the tracking
tpcI -SvtIt SsdIt : only SSD hits used in the tracking

The tracking parameters are :

for the Z direction : sigma_z = 0.0049 (0.07*0.07)
for the r/phi direction : sigma_r/phi = 4e-6 (0.002*0.002)
min window = 1.
max window = 4.
Window Scale= 10.
Max chi2= 30.

Some results

Global results

The next figures are :

DCA: - here
eta, phi, length and chi2 of the primaries tracks: - here

Comparison of the DCA
We can make 2 comparison :
1. When the SSD is not in the tracking (1)
2. When the SSD is in the tracking
  - the tracking is done included the SSD (2)
  - the tracks include or not a hit (3)
The idea is that the SSD must help for the tracking with the low pt particles, so the number of primaries tracks for the low pt must increase between (1)-->(2)and (2)-->(3). As Sti accept only tracks where pt>0.1 , pt=0.1 is the minimum value.
The next figures are :
- pt <= 0.4 : - here
- pt > 0.4 && pt <= 0.7 - here
- pt >0.7 && pt <= 1 - here
  
  Figure 1 : pt <= 0.4 Figure 2 :pt > 0.4 && pt <= 0.7 Figure 3 :pt >0.7 && pt <= 1
  
  From those plots, we can see that :
  - When the ssd is not included in the tracking and when it is included but the tracks has no ssd hit are the same, for the 3 ranges
  - When the tracks include a SSD hits (plots of the bottom) ,the DCA decrease
  to do list : see the number of entries to quantify
  Last modified: Thu Apr 20 11:38:56 EDT 2006


Figure 1 : pt <= 0.4	Figure 2 :pt > 0.4 && pt <= 0.7	Figure 3 :pt >0.7 && pt <= 1

The SSD Tracking Parameters

Another study

Global results

Comparison of the DCA