Backscattering Brief Report

Problems with Scintillator from Last Time

When we ran last time, two concerns were brought up with our scintillator data:

Resolution of those Problems from Michael Betancourt's work this summer

Additional systematic effects

Final Plots

The plots from Mike's and my analysis, along with G4 and Penelope curves provided by Junhua and Seth are included below (data and MC compilation by Junhua):

Summary and Plans

With these new plots in hand, we intend to write a brief report for Phys. Rev. C updating our previous work with these new results on scintillator.

The main points above and the final plots would be included in this report. I draw your attention to the plot comp_PEN_scint.eps which previously contained a rescaling factor 1.4 and now contains a rescaling factor 1.2. This factor caused us considerable consternation last time, and I feel it is now well in hand. (I'd also note that it didn't change much outside the 12% systematic uncertainty in normalization we were assigning last time, and would again assign this time.)

One additional issue which we have not addressed since last time is the behavior of Penelope at low energy (although this is addressed in detail in Seth's thesis in particular for Be). I'm not sure if we should consider having a bit closer look in particular for scintillator which contains hydrogen. A concern previously was the tendency of secondary electron corrections for lighter materials to be very large in Penelope, but virtually non-existent in G4.

Assuming we do not do more study of Penelope/G4 discrepancies, I think a reasonable schedule would be:

I would generate the first draft based on our previous article and Mike's SURF report.

Any comments on the work of this summery or on the figures (before I spend a lot of time generating the first draft) would be greatly appreciated.

Jeff Martin

Nov. 22, 2004.