GWU Status Report: 6-27-07

Item 1

Thickness of primary collimator (again): We re-evaluated the background versus primary collimator thickness for the CuPb collimator, results for 5, 10, 15, and 20 radiation lengths shown in the plots below or you can see the table here. When a lintel is used, it means a 15 radiation length Pb lintel.

Conclusion: NB: suppressed zero! FOM is essentially insensitive.	Conclusion: With a lintel (blue points), 10, 15, and 20 radiation lengths are the same. However, for 5 and 10 radiation lengths we depend on the lintel much more.
Conclusion: With a lintel, the photon backgrounds are all the same (blue points), but 5 and 10 radiation lengths depend on the lintel more. For electrons (red points), 15 radiation lengths seems best	Conclusion: Same story. Moller electrons will decrease when a shielding wall is added.

Conclusion: Overall, for 5 and 10 radiation legnths we depend on the lintel a lot. However, it seems like we can get by with using 15 radiation lengths.

Item 2

Line of sight? This is an image looking upstream from the Cernkov along the angle of the accepted electrons - is this a problem?:

Can see through 2nd octant of coll. 3 through 3rd octant of coll. 2 into space upstream of the primary collimator. Can eliminate by extending collimator 1 to 80 cm (previously 43.18 cm):

Item 3

Up to this point, we have only been generating events in the theta range 5-14 degrees, which covers the extreme rays through the primary collimator. We should have been including everything that gets through the first collimator, which we determined to be covered by the range 2.5-14.5 degrees in theta. Table's 3 and 4 show how this affects the backgrounds.

Plots of elastic and inelastic backgrounds for 5-14 degrees (black points) and 2.5-14.5 degrees (green points) without a lintel (left) and with a lintel (right): [can click on image for full size]

Conclusion: When opening the range from 5-14 to 2.5-14.5 as long as we are using a lintel there is no significant change. We will start using this range.

Table 3: Theta range 5-14 degrees w/o lintel with lintel Rate (MHz) 801.995 802.237 < Q^2 > 0.025753 0.025768 Error (%) 4.3087 4.3074 Elastic Photons (%) 0.20796 +/- 0.00519 0.14824 +/- 0.00477 Elastic Photons from coll. region 0.06864 +/- 0.00269 0.00583 +/- 0.00069 Inelastic Photons (%) 0.02771 +/- 0.00141 0.01087 +/- 0.00088 Inelastic Electrons (%) 0.10833 +/- 0.00536 0.11787 +/- 0.00561 Moller Photons (%) 0.87131 +/- 0.03194 0.18208 +/- 0.01431 Moller Electrons (%) 1.42232 +/- 0.08872 1.08812 +/- 0.08066

Table 4: Theta range 2.5-14.5 degrees w/o lintel with lintel Rate (MHz) 802.204 799.045 < Q^2 > 0.025757 0.025740 Error (%) 4.3092 4.3159 Elastic Photons (%) 0.23705 +/- 0.00850 0.14343 +/- 0.00687 Elastic Photons from coll. region 0.07852 +/- 0.00423 0.01127 +/- 0.00161 Inelastic Photons (%) 0.03112 +/- 0.00118 0.01048 +/- 0.00062 Inelastic Electrons (%) 0.12426 +/- 0.00470 0.11595 +/- 0.00448 Moller Photons (%) 0.94076 +/- 0.03043 0.18676 +/- 0.01277 Moller Electrons (%) 1.71436 +/- 0.07785 1.45482 +/- 0.07107

Item 4

I think I have been able to implement Juliette's codes for reading in the new field map.

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