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coulomb

Modification of Coulomb corrections 05/15/06

The energy shift was changed to the same as that used in
A. Aste and J. Jourdan, Europhysics Letters, 67 (5), pp753-759 (2004)
(NB proper proton boost was included with these results)
Setting
 Q2
 Y_c
 Y new energy shift
4agold
 1.1
 33.7635 +- 0.172718 33.9866 +- 0.173367
1agold
 2.15
 15.5426 +- 0.0823212
 15.617 +- 0.0824693

Then the focussing factor was added = (1+1.5*alpha*Z/R/Ebeam)**2, on top of the previous energy shift change.
Setting
 Q2
 Y new energy shift
 Y new focus factor
 Y_focus/Y_nofocus
 (k_i_eff/k_i)**2
4agold
 1.1
 33.9866 +- 0.173367
 34.423 +- 0.175593
 1.0128
 1.0130
1agold
 2.15
 15.617 +- 0.0824693
 15.7777 +- 0.0833179
 1.0103
 1.0104



Yields with the original SIMC 05/15/06

The yields with the original form of the Coulomb corrections (Y_c), and without (Y_nc), are shown below
Setting
 Q2
 Y_c
 Y_nc
 Yc/Ync
 (k_i_eff/k_i)**2
4agold
 1.1
 35.2785 +- 0.174364
 36.0433 +- 0.177847
 0.979
 1.0130
1agold
 2.15
 15.0271 +- 0.0762218
 15.2798 +- 0.0774787
 0.983
 1.0104
3agold
 3.0
 3.57761 +- 0.0182548
 3.71562 +- 0.0189825
 0.963
 1.0104
4acopper
 1.1
 81.716 +- 0.407188
 82.1748 +- 0.409581
 0.994
 1.0068
1acopper
 2.15
 34.7642 +- 0.178414
 35.0252 +- 0.179221
 0.993
 1.0054
3acopper
 3.0
 8.27303 +- 0.042792
 8.50825 +- 0.0439159
 0.972
 1.0054


Results with and without Coulomb corrections 04/29/06

SIMC was run with Coulomb corrections turned off (using_Coulomb = 0) and compared to the previous results with Coulomb corrections turned on.

The results below have NO Pauli blocking or FSI corrections.  They, do have the missing mass shifts suitable for not using Pauli blocking.  The missing mass shifts were unchanged when Coulomb corrections were turned off.

Conclusions:  The missing mass distributions and yields are not affected significantly by Coulomb corrections.  The changes in the missing mass distributions are so small that it looks like the shifts do not need to be changed when Coulomb corrections are turned off.  The yields changed, but within statistical uncertainties.    Some distributions changed, however, like Q2 and phipq for gold.

Missing mass without Coulomb corrections
mmx shift
 1H 2H C Al Cu Au
missmass shift
2H C Al Cu Au

Missing mass with Coulomb corrections
mmx shift
 1H 2H C Al Cu Au
missmass shift
2H C Al Cu Au


More results without Coulomb corrections
NUCLEON mmx cuts norm yield iteration
 1H 2H C
 Al
 Cu
 Au Transp.
 		A/2H
 A/C
 A/Cu
 Alpha
 Alpha (H_to_Al)
 Alpha (Al_to_Au)
NUCLEAR missmass cuts norm yield

2H C Al Cu
 Au Transp. A/2H A/C A/Cu Alpha Alpha (H_to_Al) Alpha (Al_to_Au)
Missmass cuts by eye
 norm yield

2H C Al Cu Au Transp. A/2H A/C A/Cu Alpha Alpha (H_to_Al) Alpha (Al_to_Au)

More results with Coulomb corrections
NUCLEON mmx cuts norm yield iteration
 1H 2H C
 Al
 Cu
 Au Transp.
 		A/2H
 A/C
 A/Cu
 Alpha
 Alpha (H_to_Al)
 Alpha (Al_to_Au)
NUCLEAR missmass cuts norm yield

2H C Al Cu
 Au Transp. A/2H A/C A/Cu Alpha Alpha (H_to_Al) Alpha (Al_to_Au)
Missmass cuts by eye
 norm yield

2H C Al Cu Au Transp. A/2H A/C A/Cu Alpha Alpha (H_to_Al) Alpha (Al_to_Au)



Status of the default SIMC 04/29/06 (rev. 05/01/06)


I looked through the SIMC code and the incident and scattered electron energies are corrected for the Coulomb potential.

Here is 1 1/2 pages on the current status of SIMC Coulomb corrections.

So, it looks like there is no deflection of the electron angle in SIMC (see John's thesis, pp 156-157)  (After contacting John A., the eikonal approximation is ok.  He needed to consider deflections in his work because the cross section decreased very rapidly for x>1.)

Also, I do not see anywhere the enhancement in the cross section by the factor (k_i^eff / k_i)**2 (see Dipangkar's thesis, pg 160).

Coulomb corrections to the outgoing pi+ are not present in SIMC.  This changes the energy and momentum of the pi+ by about 20 MeV for the gold target.  (After contacting John A. it now makes a lot of sense that Coulomb energy shifts are not applied to the hadron.  This is already included to first order in the separation/binding energy for the hadron.  The mass of the target nucleus and the recoil nucleus are inputs to SIMC, and Coulomb corrections are already included in the energy and momentum conservation used to calculate the final kinematics.)