"Case 1" is reported to be the standard VT collimator from line 20, with the addition of a 50 cm thick lead shield wall with a window having 2 cm and theta_max = 10.53. On his computer, I found a geometry file called "qweakfinal.euclidvt." This was used to reproduce his values.
- a) as claimed but with a 50 cm concrete wall
- b) as claimed
- c) Yongguang's values
- d) Actual - using "qweakfinal.euclidvt", which has a theta_max=10.25, 2 cm clearance + 4 cm W lining the window
- e) Actual - without W lining
Table 1: Case 1 Comparison
| Elastic Photons | Elastic Photons from coll. region | Inelastic Photons | Inelastic Electrons | Moller Photons | Moller Electrons | |
| a | 0.2255% +/- 0.0053% | 0.0448% +/- 0.0020% | 0.0336% +/- 0.0005% | 0.2341% +/- 0.0031% | - | - |
| b | 0.1954% +/- 0.0050% | 0.0394% +/- 0.0019% | 0.0146% +/- 0.0003% | 0.0623% +/- 0.0015% | 0.5134% +/- 0.0236% | 0.1492% +/- 0.0190% |
| c | 0.21% | 0.038% | 0.014% | 0.12% | 0.44% | 0.183% |
| d | 0.2091% +/- 0.0052% | 0.0383% +/- 0.0018% | 0.0138% +/- 0.0003% | 0.1194% +/- 0.0022% | 0.4366% +/- 0.0216% | 0.1831% +/- 0.0259% |
| e | 0.2017% +/- 0.0051% | 0.0378% +/- 0.0018% | 0.0188% +/- 0.0004% | 0.0738% +/- 0.0018% | 0.5320% +/- 0.0254% | 0.2432% +/- 0.0322% |
Important Point: The rates reported for "case 1" in his 12-30-05 status report come from a window design that has 2 cm clearance and 4 cm tungsten lining the edge of the window and theta_max = 10.25.
Conclusions
- Going from 1a to 1b there is a definite reduction in backgrounds seen by replacing the concrete shielding wall with a lead wall.
- Comparing 1c and 1d we can see that we have identified the geometry file Yongguang used to generate the results he reported.
- Going from 1d to 1e the tungsten lining decreases all backgrounds except it increases electrons from inelastic reations.
- 1b gives the lowest rates for all backgrounds except for photons from Moller events.
"Case 2" is reported to be different from case 1 by:
and should have a shield wall window with 2 cm clearance. Yongguang does not provide or reference this geometry file. However, in his 12-30-05 status report Yongguang links the geometry file for case 3 (see below). The only difference between case 2 and case 3 is the lintel. Ideally, we should be able to get a geometry file for case 2 by commenting out the lintel in case 3.
- moving the primary collimator 25 cm upstream
- changing the primary collimator to 5.25 cm thick tungsten
- adding 11.2 cm thick non-defining lead shielding behind the primary collimator
- reducing theta_max to 10.25
For Case 2 we have
- a) Yongguang's values
- b) Case 3 from his report with lintel commented out
- c) Case 3 from his report with lintel commented out and adding W lining
- d) Case 3c with lintel commented out, wall 2 cm + 4 cm W (Case 3c has a geometry file identified in his report, describes the correct geometry, and produces the same results that Yongguang reported.)
Table 2: Case 2 Comparison
| Elastic Photons | Elastic Photons from coll. region | Inelastic Photons | Inelastic Electrons | Moller Photons | Moller Electrons | |
| a | 0.2% | 0.032% | 0.015% | 0.037% | 0.38% | 0.18% |
| b | 0.1970% +/- 0.0051% | 0.0283% +/- 0.0016% | 0.0182% +/- 0.0004% | 0.0714% +/- 0.0019% | 0.3133% +/- 0.0178% | 0.1301% +/- 0.0250% |
| c | 0.2019% +/- 0.0054% | 0.0341% +/- 0.0018% | 0.0141% +/- 0.0004% | 0.1117% +/- 0.0022% | - | - |
| d | 0.2019% +/- 0.0054% | 0.0341% +/- 0.0018% | 0.0141% +/- 0.0004% | 0.1117% +/- 0.0022% | - | - |
Conclusions
- It is not clear what geometry file Yongguang used to obtain his results. However, the ntuple identified as being for this geometry file gives the reported values.
- Comparing 2c and 2d shows consistency in what we are doing.
- 2b gives the lowest rates for the listed backgrounds and they are lower, or very similar to those in 1b.
"Case 3" is reported to be different from case 2 by the addition of a 5.25 cm thick x 16 cm high x 56 cm wide tungsten lintel positioned at Z = -80 cm.
As mentioned before, this geometry file is in his report and describes the claimed geometry. However, this geometry file does not produce the rates reported. We have
- a) Yongguang's values
- b) Case 3 from the report
- c) Case 3 from the report with 4 cm W
Table 3: Case 3 Comparison
| Elastic Photons | Elastic Photons from coll. region | Inelastic Photons | Inelastic Electrons | Moller Photons | Moller Electrons | a | 0.16% +/- 0.0045% | 0.004% | 0.013% +/- 0.00032% | 0.041% +/- 0.0014% | 0.11% +/- 0.01% | 0.125% +/- 0.036% |
| b | 0.1709% +/- 0.0050% | 0.0018% +/- 0.0003% | 0.0175% +/- 0.0004% | 0.0689% +/- 0.0018% | 0.1117% +/- 0.0118% | 0.1184% +/- 0.0265% | c | 0.1705% +/- 0.0052% | 0.0023% +/- 0.0004% | 0.0139% +/- 0.0004% | 0.1171% +/- 0.0023% | - | - |
Conclusions
- Once again, it is not clear what geometry file Yongguang used to obtain his values. However, the ntuple identified as being for this geometry does gives his reported values.
- We will use the values we are able to produce.
The values we are able to produce for the stated geometries are
Table 4: New values for Case's 1-3
| Elastic Photons | Elastic Photons from coll. region | Inelastic Photons | Inelastic Electrons | Moller Photons | Moller Electrons | |
| Case 1 | 0.1954% +/- 0.0050% | 0.0394% +/- 0.0019% | 0.0146% +/- 0.0003% | 0.0623% +/- 0.0015% | 0.5134% +/- 0.0236% | 0.1492% +/- 0.0190% |
| Case 2 | 0.1970% +/- 0.0051% | 0.0283% +/- 0.0016% | 0.0182% +/- 0.0004% | 0.0714% +/- 0.0019% | 0.3133% +/- 0.0178% | 0.1301% +/- 0.0250% |
| Case 3 | 0.1709% +/- 0.0050% | 0.0018% +/- 0.0003% | 0.0175% +/- 0.0004% | 0.0689% +/- 0.0018% | 0.1117% +/- 0.0118% | 0.1184% +/- 0.0265% |
Conclusion
- Comparing cases 1 and 2 shows no clear advantage to changing the primary collimator.
- Comparing cases 2 and 3 shows significant reduction in all backgrounds except for those from inelastic processes.
Next step
- Reanalyze these data with correct photoelectron production efficiency for photons. Preliminary analysis shows this has ~5% effect.
- Try geometry with collimator as described in case 1 adding the lintel.