1. Pi0 Simulation for BigCal
Jixie Zhang
July 23, 2015

2. Outline https://github.com/jixie/sane_geant3_mc
1. Add more pi0 simulated events. 367M events now.
2. Extract the yield ratio using wiser cross section and Oscar's scaling fit cross section respectively. Compare these two results to each.
Compile and run the code in 64-bit CentOS 6.5
Comparison is now on going.

3. Definition of Electron Cut
In the geant3 simulated ntuple, an electron is defined as the following:
A) cer_npe > 60 && cer_npe < 110
B) E_m > 0.5
cer_npe is the number of photon electron
E_m is the energy deposited in the BigCal

4. About Thrown Events

5. Number of Atoms in The Target Nose
Material Z
Thickness
(cm)
Density (g/cm^3)
Moll-Mass (g/moll)
Number of Atoms (NA)
Al end caps 14
0.013x2.54
2.7
26.982 H 1
1.8
NH3=0.867
NH3=
x 3 N 7
LHe 2
0.145
4.003
A) 60% packing fraction;
B) Target cell length is 3 cm;
C) The liquid helium thickness outside the cell is 0.5 cm on both ends;
D) Aluminum include 2 end caps(1.5 mil), 4k-shielding (1 mil) and target nose (4mil).
This table shows the relative relation among materials in the target cell. If normalized to N14, the result is:
H : He : N : Al = 3 : : 1 :

6. Weight Thrown Events to Match Cross Section Shape
1) Fill four 3-D histograms, H3XS, of E:CosTh:phi, the content in each 3-D grid is the averaged cross section of H, He, N and Al.
2) Sum these four 3-D histograms, weighted by the number of atoms in the target to get H3XS_total. Integrate the resulting 3-D histogram to get total cross section, XS_total.
3) Fill four 3-D histograms, H3N, of E:CosTh:phi, weighted by the number of atoms in the target. Add them together to get H3N_total. The integral of H3N_total, N_total, is the total number of thrown events.
4) Scale H3XS_total such that its integral equal to that of H3N_total, then H3Weight=H3XS_total/H3N_total. This weighting will match thrown events into the shape of cross section. Later on, use H3Weight to weight each event in the analysis.
5) Charge is proportional to N_total/XS_total. The yield from BigCal after all cuts will be scaled by Charge.

7. Averaged XS within E-cosTh bin
Scaling Fit

8. 100 nA
Scaling Fit

9. Log file: Wiser All TotalXS= 0.0554312 H TotalXS= 0.0027661 weight= 3
He TotalXS= weight=
N TotalXS= weight=
Al TotalXS= weight=
_e: TotalXS= N_Thrown= e+07 Lumi_14N_100na= e+34
To match 100na x 1000 seconds of charge: fChargeScale=
TYPE N_thrown N_bigcal N_bigcal_cut N_e+_or_e N_e+
N_thrown
N_w_tg e e e e
N_w_tgNdistr e e e e
N_q_scaled e e e
tg/tgNdistr
All TotalXS=
H TotalXS= weight=
He TotalXS= weight=
N TotalXS= weight=
Al TotalXS= weight=
_pi0: TotalXS= N_Thrown= e+08 Lumi_14N_100na= e+34
To match 100na x 1000 seconds of charge: fChargeScale=
TYPE N_thrown N_bigcal N_bigcal_cut N_e+_or_e N_e+
N_thrown
N_w_tg e e e e e+06
N_w_tgNdistr e e e e
N_q_scaled e e e e e+06
tg/tgNdistr

10. Log file: Scaling Fit All TotalXS= 0.0554312
H TotalXS= weight=
He TotalXS= weight=
N TotalXS= weight=
Al TotalXS= weight=
_e: TotalXS= N_Thrown= e+07 Lumi_14N_100na= e+34
To match 100na x 1000 seconds of charge: fChargeScale=
TYPE N_thrown N_bigcal N_bigcal_cut N_e+_or_e N_e+
N_thrown
N_w_tg e e e e
N_w_tgNdistr e e e e
N_q_scaled e e e
tg/tgNdistr
All TotalXS=
H TotalXS= weight=
He TotalXS= weight=
N TotalXS= weight=
Al TotalXS= weight=
_pi0: TotalXS= N_Thrown= e+08 Lumi_14N_100na= e+34
To match 100na x 1000 seconds of charge: fChargeScale=2.3348
TYPE N_thrown N_bigcal N_bigcal_cut N_e+_or_e N_e+
N_thrown
N_w_tg e e e e e+06
N_w_tgNdistr e e e e
N_q_scaled e e e e e+06
tg/tgNdistr

11. BigCal RCS: 24 rows x 30 (columns) Y=0 at geant3 code
Protvino: 32 rows x 32 (columns)
different colors indicating the groupings of the trigger channels

12. Binned by groups of blocks
Coded by 2-digit row index and
2-digit column index. i.e. This is 0101
Y=0 at geant3 code
Protvino: 32 rows x 32 (columns)
Grouped by: 8(rows) x 8 (columns)
RCS: 24 rows x 30 (columns)
Grouped by: 6(rows) x 6 (columns)

13. PROT Yield for Electron

14. PROT Yield for Pi0

15. RCS Yield for Electron

16. RCS Yield for Pi0

17. PROT Yield Ratio: Pi0 to Electron

18. RCS Yield Ratio: Pi0 to Electron
Strong dependence on angle

19. PROT Pi0 Fraction: Pi0 to Total

20. RCS Pi0 Fraction: Pi0 to Total

21. Pi0 Cross Section: Scaling Fit Vs Wiser
xsn is from scaling fit

22. Yield Ratio: Scaling Fit Vs Wiser
Scalling Fit

23. Yield Fraction: Scaling Fit Vs Wiser
Scalling Fit

24. 64-bit sane-geant3
1.  gxcs.f: Added a missing "EXTERNAL GBRSGE".  Without that external, the second to last CSEXT was crashing
2.  uginit.f: Put the address argument of every FFKEY call into a common block.

25. 64-bit vs 32-bit

26. Summary
367M pi0 events have been simulated in geant3. Statistics is enough for 2x2 binning in the PROT and RCS.
Oscar's scaling fit photon production cross section is about a factor of 0.5 to Wiser's.
Yield ratio have strong dependence on theta angle. Binning by 2x2 in RCS and PROT might not be fine enough.
Yield ratio can be fit by a smooth polynomial function to avoid point to point fluctuation.