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2023 Sep 13 (Notes from Mini KaonLT meeting on HeeP offsets, physics_iterate.f  and weight iteration)

Notes by Richard

Present:
Ali
Garth
Richard
Vijay
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Meeting to discuss HeeP offsets for Garth's analysis (mainly the discrepancy between Richard and Vijay's low energy HeeP results)
Also discussing the physics_iterate.f script for cross section functional form iterations

- HeeP Offsets
	- Ali will check with his replays/simc
	- If Ali and Richard match...
		- We will need to compare input files for simc and hopefully it is easy to find differences with Vijay
		- If that doesn't work we will then need to match our simc versions to make sure they match and address any differences
	- Once SIMC is matching, we should also compare replay param files, etc. to see where these differences arise
	- Ali and Richard: Check arc measurement is what is written in standard.kinematics for lower energies
	- Richard: shorten range of fits so they are just the peak
	- Richard: Increase sig figs to 5 for plots to better distinguish between similar mean values
	- Richard: Rerun SIMC without recon_hcana script to see if they match Vijays
		- The recon_hcana script changes calculation of emiss, W, and Pmx,y,z so we should see a change
	- Richard: Double check that there are no offsets of SIMC input files
	- Richard: Write-up email that compares recon_hcana and hcana calculations for emiss, pmx,y,z, W
- lt_analysis
	- Avg Q2, W, t per t-bin in data and SIMC. Compare to make sure they look similar, but only data goes through average_kinematic.f
		- The ratio of data/simc is used with the data averages per bin for xsects not SIMC. SIMC is only needed for the yields of the ratio
	- physics_iterate.f
		- No Fermi momentum! Remove all references to this
		- Virtual photon flux factor, should be consistent with elastic (based off data)
		- Code lines: 362-97, these read in the initial set of parameters. This assures you never need to run simc again. Separate code to redo this with new parameters (see recalculate weights below).
		- This code does not need to be re-run!
		- For kaon, change routine at top to peek and replace physics_kaon with this code.
		- For kaon, replace all mass of pion with kaon.
		- For kaon, in Makefile, replace physics_kaon with physics_iterate
		- For kaon, no need to remove physics_kaon in event.f
		- Create new branch for simc with physics_iterate instead of physics_kaon
		- The returned variable of physics_iterate needs to be called in event.f
		- This return value is the cross section that is the basis of the weight
	- event.f
		- main%sigcc = peek(vertex, main) is the read in for the physics_iterate return
		- Line 1915-16: This is where the weight is calculated
	- Recalculate weights
		- Bill has C++ code based off FORTRAN code
		- Vijay has the code (knows the location), which he can share
		- Iterate each Q2 separately, with their own parameters
		- Each iteration, simc needs new weight applied, then rebinned and then recalculate the yields.
		- The new parameters for the weights are called in xsects via the xmodel
		- xmodel should match the functional form of physics_iterate, initially (may change for kaon later if things dont converge). xmodel does not need to be adjusted each iteration, only the parameters that are read in.
		- For kaon, add mass of lambda in xmodel. In general, check all masses of FORTRAN scripts