central_sigma

Corrected central cross section 03/22/06 (rev. 03/30/06)

Ok, I worked out where I went wrong in bin centering the simc cross section. In calculating the solid angle in my kumac, I used sin(theta)*ssxptar*ssyptar when I should have used just ssxptar*ssyptar. Here are my results with the new kumac. Nb one may also need the fetchallmc1 script (use chmod +x fetchallmc1 on this script). The new kumac was called with the binc.kumac macro.

Hydrogen elastic diff cross section (infile)
My kumac 1.02141E-05 ub /sr
Simc output 10222 nb/GeV2/sr2
Mean sigcc 1.02128E-05

H(e,e'pi) 5 fold diff cross section (infile)
My kumac 5.0587E-06 ub /sr /MeV /sr
Simc output 927.09 nb/Gev2/sr2
Mean sigcc 5.05829E-06

Au(e,e'pi) 6 fold diff cross section (infile)
My kumac 1.54226E-06 ub /GeV /sr /MeV /sr
Simc output 947.127 nb/Gev2/sr2
Mean sigcc 4.3382E-06

Central cross section 03/22/06

Radiation, energy loss, transport in the spectrometers was turned off, and particles were generated in the central part of the spectrometers.

I set up a kumac to measure the simc normalized yield in a small part of the spectrometer's phase space. However, I get very different results to the cross section output by simc in the runout file.

Hydrogen elastic diff cross section
My kumac 0.02014 nb/sr
Simc output 10222 nb/GeV2/sr2
Mean sigcc 1.02128E-05

There is a factor of 10^6 that needs to be included with the SIMC output, this is because simc assumes the cross section needs a conversion from microbarn to nb and MeV2 to GeV2. The cross section does not need the conversion from MeV2 to GeV2 because it is only a 2 fold differential cross section. After this correction to simc, there is still a factor of 2 between the two values.

H(e,e'pi) 5 fold diff cross section
My kumac 19.10 nb/GeV/sr2
Simc output 927.09 nb/Gev2/sr2
Mean sigcc 5.05792E-06

This cross section is a good check because the simc output assumes pfermi is zero for the central event used to calculate this cross section. However, I don't see where a factor of 50 could be included. It seems the SIMC output should be divided by 1000 because only one conversion from MeV to GeV is required.

Au(e,e'pi) 6 fold diff cross section
My kumac 12205.4 nb/GeV2/sr2
Simc output 947.127 nb/Gev2/sr2
Mean sigcc 4.30798E-06

Again, not sure what is going on here. One reason could be that simc assumes pfermi is zero for this calculation, whereas my kumac uses the events in the ntuple that fall in a small central region of the spectrometers.