Application of the SVT simulation to Run II Data
Due to the lack of the SVTD bank in most of the recent data sets
appears clearly, for our final scope, the need to have some
alternative information about the SVT reconstructed tracks. We decided
to run the SVTsim_standalone.exe program, written by G. Punzi, on the hits
contained in the SIXD Storable Bank, for the few runs which have it
available.
Our aim is to give a sort of validation of this new quick simulation,
based on the comparison with the real data in the SVTD bank.
This task appears necessary in order to improve our study of SVT
performance on very crowded events, like multijets or Higgs
associated production
with vector bosons in the 4-jets final state.
Other Technicalities
 |
| Current status of activity of the SVX layers. On the x axis is the sector number, on the y axis the layer number. |
At this time, SVT is able to reconstruct tracks only if there are
hits in all of the activated silicon layers (layers: 0, 1, 2, 3).
It is strongly necessary to have a map of the SVX-II sectors
that are already in use, and consequently of those layers that could
receive and register hits, in order to correct the rate estimates
For Run II data that belong to the Stream G:
-> run 123499
-> run 123618
-> run 123622
-> run 123623
-> run 123842
-> run 123852
-> run 123859
-> run 123868
-> run 123901
As is clear from the picture on the right, we do not yet have the full
silicon detector operational.
For the runs examined here the percentual of active layers for each
half-barrels are:
-> half-barrel 0: 66.6 % of active layers;
-> half-barrel 1: 75.0 % of active layers;
-> half-barrel 2: 33.3 % of active layers;
-> half-barrel 3: 66.6 % of active layers;
-> half-barrel 4: 50.0 % of active layers;
-> half-barrel 5: 25.0 % of active layers;
In order to compute rate estimates for the
proposed SVT selection at Level 2, we need to not just count how many
tracks with impact parameter above 100 microns we find in each event,
but extrapolate to the optimal situation we hope we'll be facing in
a few months. To do that, we extract the distribution of the number
of tracks per event in each half-barrel, after correcting for the fraction
of azimuth not yet covered, and calculated the expected number of tracks that
would be found in an optimal SVX-II running configuration.
That number is extracted by runnig a random number over a poisson distribution
with mean equal to the extimated number of lost tracks. Then a distribution
of the impact parameters is performed.
There are different cases on which we should correct our extimation
of rates event per event.
If between all tracks we have just found two different tracks with d0
greater than 100 microns, our trigger will shot and the event will pass
our SVT requirements. It does not mind is other tracks would be lost, for
now.
Critical is instead of this, the situation in which we find only one tracks
satisfying our requirements. Other tracks that would be able to make the
trigger shoot maybe are lost trought the dead zone of SVX-II. To understand
such a possiblity we pull N,(= number of expected lost tracks) random number
of impact parameter, following the general IP distribution of all the tracks
of the considered event. Then we
take in accounts only those that are greater than 100 microns. If we find
another track the trigger will be able to shoot again.
In the case with no SVT "trigger" tracks we can procede as before but now searching
for two random generated IP greater than 100 microns.
Results:
 |
Extrapolated rates in input to L3. Calorimetric L2 requirements already applied.
Top Left: IP distribution of the greatest IP tracks
Top Right: IP distribution of the second greatest IP tracks
Bottom Left: Extrapolated rates in input to L3 as a function of the IP cut on the
greatest IP track
Bottom Right: Extrapolated rates in input to L3 as a function of the IP cut on the
second greatest IP track |
Here we show the the input rate to Level~3 summuing the calorimetric
and SVT requirements as a function of the cut we want to do on the IPs.
Top Left: IP distribution,event per event, of the greatest IP track
Top Right: IP distribution, event per event of the second greatest IP tracks.
Bottom Left: L3 into rate as a function of the IP cut.
Bottom Right: L3 into rete as a function of the IP cut on the second greatest IP
tracks.
The total rate into L3 appears to be larger than expected:
it is 3-4 Hz instead of the
extimated 1.5 Hz. This fact could maybe understood cosidering the large superstrips
size used.
Some correction are already pending waiting for possible corrections to be applied due
to the result of the comparison of SVTsim with SVTD Storable_Bank.
Useful Links
SVT Pisa's Home Page
Back to the multijet trigger web page
Giorgio Cortiana
Last modified: Wed Sep 12 15:20:18 CDT 2001