BigBite Optics #7

Matrix elements "[TgDp|Fp??]"

Up until now I was using elastic runs to determine matrix elements for the TgDp variable. This was not the best approach, because I only have few good elastic runs that I was able to use. Beside that, elastic runs covered only small portion of the BigBite acceptance. Therefore I decided to use Doug's advice and use quasi-elastic deuterons runs for my calibration. Before I started writing code for this, I decided to check, how well missing-mass-peak reconstruction works with current matrix elements. It turns out, that it works well with 2GeV data but fails poorly for 3GeV data. Here are the results: 

MissingMass = 0.9304 GeV
SigmaMissingMass = 0.0134 GeV
1.) 2.)

In order to get better matrix elements I decided to write a minimization code in Mathematica, but again, it did not work well. Therefore I decided to rewrite this code to Matlab. This is still work in progress. I have already written the code, but still need to check for any bugs. So far, it seems to be working fine with 70 fitting parameters and more than 2000 fitting points. This is far more promissing than Mathematica. I hope this calibration will be finished by the end of next week.

3.) 4.)

Matrix elements "[TgPh|FpPh]" and "[TgTh|x]"

I have also determined next iteration of the matrix elements for the TgTheta variable. Since I was using Mathematica for my minimization, I was able to consider only matrix elements up to the second order. At this point my optics matrix consideres second order matrix elements for both variables TgTh and TgPh. I believe that with new Matlab code (or Ge's code), I will be able to determine higher order terms.). Here is my current picture of the sieve-pattern.

5.) 6.)

Since transport matrix seems to work well in the central region of the sieve, we were wondering, how many events do we loose if we consider only this innter part of the acceptance. To test this, I have taken 12C run #3491 and Deuteron quasielastic run #3151 and calculated the ratio between the number of events detected in the focal plane with cut on the sieve and without it. I have also considered two other options: with and without cut on the coincidence events. In any case, the ratio between the two is always approximately 50%.

12C run #3491 - Sieve Cut / No cut on Coincidence Trigger

7.) 8.) 9.)

12C run #3491 - Sieve Cut / With cut on Coincidence Trigger ((DL.evtypebits &32) = 32)

10.) 11.) 12.)

12C run #3151 - Sieve Cut / With cut on Coincidence Trigger ((DL.evtypebits &32) = 32)

13.) 14.) 15.)

12C run #3151 - Sieve Cut / Without cut on Coincidence Trigger

16.) 17.) 18.)
Last modified: 03/31/10