1. External alignment
Maya Shimomura (ISU)
12/03/15
RIKEN VTX meeting

2. Alignment—check the run dep.
Condition and Selection
Run
Reconstruct from PRDF files ( under /phenix/zdata03/phnxreco/VTX/prdf/eventdata/)
Au+Au peripheral collision (10<BBC charge<200 )
-10<bbcz<10
Suppose the magnetic filed is uniform. (0.9 Tesla)
Coordinate systems are matched between VTX and CNT.
OffsetVtxToCnt :(-0.169,-0.122,0.)
X Y vertex
Xoffset = and Yoffset = for West Wrong
Xoffset = and Yoffset = for West
Hot dead map is not applied.
Z vertex --- VTX vertex
12/03/15
RIKEN VTX meeting

3. DCA distribution before and after z alignment from Beam Center
Run West
Run West
Φ[rad]
Run East
Φ[rad]
Run East
Φ[rad]
Φ[rad]
Looks like there is some offset. I am checking the beam center.
 Beam Center is slightly difference. Change the beam center.
12/03/15
RIKEN VTX meeting

4. DCA distribution before and after z alignment from Beam Center (corrected)
Run West
Run West
Φ[rad]
Run East
Φ[rad]
Run East
Φ[rad]
Looks OK.
Φ[rad]
12/03/15
RIKEN VTX meeting

5. Peak position comparison
New run looks to be aligned even better.
12/03/15
RIKEN VTX meeting

6. Peak σ comparison New run 349040 looks more stable. 12/03/15
RIKEN VTX meeting

7. Peak position comparison
BC : dϕ is calculated from beam center for all events.
Vv : dϕ is calculated from VTX vertex for each events.
12/03/15
RIKEN VTX meeting

8. Peak σ comparison
BC : dϕ is calculated from beam center for all events.
Vv : dϕ is calculated from VTX vertex for each events.
12/03/15
RIKEN VTX meeting

9. Summary and Outlook Run dependence is studied comparing two runs.
No systematic difference
Run looks good to be used.
Make dϕ iterated correction after hidemitsu’s iteration.
Check beam center dependence and run dependence more.
Try r correction with divided ϕ smaller than a ladder.
Code preparation for QA at DST production.
12/03/15
RIKEN VTX meeting

10. Back Up
12/03/15
RIKEN VTX meeting

11. Peak position comparison
BC : dϕ is calculated from beam center for all events.
Vv : dϕ is calculated from VTX vertex for each events.
12/03/15
RIKEN VTX meeting

12. DCA distribution before and after z alignment from Beam Center
Before West
After West
Φ[rad]
Φ[rad]
Before East
After East
Φ[rad]
Φ[rad]
No change.
12/03/15
RIKEN VTX meeting

13. Doing now Check run dependence. Prepare the codes for QA.
Need the iteration more for dphi.
Check run dependence.
Prepare the codes for QA.
We have not understood the reason why the widths of dphi peak are different between West and East.
12/03/15
RIKEN VTX meeting

14. Both run#349369 and run#349679 are in this period.
Zero field run
Zero field run ,
Zero field run ,
Zero field run , ,349007
Both run# and run# are in this period.
12/03/15
RIKEN VTX meeting

15. Calculation details on x-y plane
hit in VTX (xvtx,yvtx)
Distance(D) between the VTX hit and the straight line projection from (xoffset1,yoffset1) along the vector u can be calculated as the cross product (vector product) of vector x and vector u.
x = (xx,xy)=(xvtx-xoffset,yvtx-yoffset)
u = (ux,uy)=(cos(ϕ0),sin(ϕ0))
D = xx*uy - xy*ux
Track from (xoffset,yoffset)
Magnetic bending correction is approximated as
bend ~ 0.5*r2/R
r: length of vector x
Since p = 0.3*B*R
with B=0.9T
p ~ 0.27*R
1/R ~ 0.27/p
bend ~ *r2/p (r in cm)
u = (cos(ϕ0),sin(ϕ0))
initial direction of the CNT track used as the seed or guide
Beam center
(xoffset,yoffset)
12/03/15
RIKEN VTX meeting

16. Central Track Cut Track quality = 31 or 63 1.0<p[GeV/c]<4.0
|pc3dphi - emcdphi |<0.02
|pc3dz - emcdz + 0.2|<5.0
RIKEN VTX meeting
12/03/15

17. Condition and Selection
Simulation -- π0 single particle simulation
Condition and Selection
Single π0 generated by Exodus
10000 events (for test)
Analysis flow is “Exodus -> PISA -> PISAtoDST -> analysis with SvxCentralTrack”
-0.5<eta<0.5 (70% is going to Central arm )
2 π (~50% is going to Central arm)
No hot-dead map is applied.
X Y vertex is (0,0)
No offset
RIKEN VTX meeting
12/03/15

18. How many tracks with 10000 π0? Decay π0  2ϒ (98.8 %)
Dalitz π0  ϒ +e++e- (1.2%)
Radiation length up to Beam pipe (0.2%)
Radiation length up to 4th layer (10%)
Acceptance (35%)
CNT tracks: =1475.6
Conversion e- up to beam pipe: =13.88
12/03/15
RIKEN VTX meeting

19. Events and tracks.
BBC z vertex
Number of tracks per event
Number of segments per event
Looks reasonable, but the number of reconstructed tracks is 268. This is too few comparing with the calculation.
12/03/15
RIKEN VTX meeting

20. DCA distributions w/wo cuts
Require B0 hit
No cut
12/03/15
RIKEN VTX meeting

21. DCA distribution with cuts
Select only electron at CNT
&& require B0 hit
Select only electron at CNT
The width became narrow.
I will apply tighter cuts.
12/03/15
RIKEN VTX meeting