Vertex determination - central region


Previous: LDRD digitization   |   Index   |   Next: different LDRD configurations

Suppose we place two 8-chip modules in the location where the barrel layers will be later. How many tracks will these modules see? The short anwer is: for a central Au-Au collision, a module measuring 64mm by 7.0 cm located at 2.5cm would see 94 tracks, and such a unit at 5.0 cm would see 29 tracks. This scales of course roughly with 1/r2

The vertex resolution in Z is roughly the pixel size (400 um) divided by sqrt(12), divided by sqrt(number of particles)


Input file: root -l ancsvx_2auau_ldrdflat.root (in ../cvs5/wrk/). It is just possible to select 6.4-mm bits of the barrel such that these are no overlaps, as shown by the red boxes

Here are the details, showing cumulative cuts: 


         AncSvx->Draw("YGLOBAL:XGLOBAL","
         abs(LAYER)<=4")

There are 21980 entries from 2 central AuAU events. 
         AncSvx->Draw("YGLOBAL:XGLOBAL","
         LAYER==1 && 
         EVENT>0")
         
         AncSvx->Draw("YGLOBAL:XGLOBAL","
         LAYER==1 && 
         EVENT>0 && 
         abs(ZGLOBAL)<3.5")
         
         AncSvx->Draw("YGLOBAL:XGLOBAL","
         LAYER==1 && 
         EVENT>0 && 
         abs(ZGLOBAL)<3.5 && 
         abs(YGLOBAL)<0.32")
         
         AncSvx->Draw("YGLOBAL:XGLOBAL","
         LAYER==1 && 
         EVENT>0 && 
         abs(ZGLOBAL)<3.5 && 
         abs(YGLOBAL)<0.32 && 
         XGLOBAL>0")

Layer 1 is at 2.5 cm. 
         AncSvx->Draw("YGLOBAL:XGLOBAL","
         LAYER==2 && 
         EVENT>0 && 
         abs(ZGLOBAL)<3.5 && 
         abs(YGLOBAL)<0.32 && 
         XGLOBAL>0")

Layer 2 is at r=5 cm.





Vertex finding - forward region

Short answer: Per AuAu collision, 82 tracks will be seen by 4 planes of the ldrd detector


Details: Bounded by bottom of station 1, top of station 4. Cut at station 4: y>6.4cm

Station 1 bound y<8.7cm

166 entries in station 4, for y>6.4 (so that they also hit station 1
Bounded by layer 4, x<3.5, which is x<1.97 cm at station 1
163 entries in station 1, for y<8.7 (so that they also hit station 4, and abs(x)<1.97. This is statistically the same as we saw in station 4.

The same procedure requiring track to go through stations 1-3 only (|x|<2.26, y<10.20)gives 198 hits. (99 per event)




Previous: LDRD digitization   |   Index   |   Next: different LDRD configurations