[G12] Photon energy reconstruction issue in MC

[Andrea Celentano]

All,
after a test without including gpp (gsim output directly to a1c), I see the same issue in MC for photon energies.
I am following exactly instructions on g12 note concerning the simulation / gpp / a1c commands, using calib_user.RunIndexg12_mk and run number 10. In the past, I also used standard g12 runindex, and I got same issue for MC.


Andrea

> On Jan 16, 2019, at 14:24, John W. Price <jprice at csudh.edu> wrote:
> 
> Hi Andrea:
> 
> Can you do a test *without* including gpp?  This might help isolate the cause of the issue.
> 
> John
> 
> -- 
> John W. Price
> Professor, CSUDH Department of Physics
> Coordinator, Science, Mathematics, and Technology Program
> 310-243-3403
> 
> On Jan 16, 2019, at 05:15, Michael Kunkel <mkunkel at jlab.org <mailto:mkunkel at jlab.org>> wrote:
> 
>> Greetings Andrea,
>> 
>> I believe you just verified what Diane Schott and I had been trying to convince other of for many years. :)
>> 
>> However, the correction for simulation is quite trivial since we already know the generated 4vector. 
>> 
>> I don’t believe the kinfit package handles this problem.
>> 
>> BR
>> MK 
>> ----------------------------------------
>> Michael C. Kunkel, USMC, PhD
>> 
>> On Jan 16, 2019, at 05:59, Andrea Celentano <andrea.celentano at ge.infn.it <mailto:andrea.celentano at ge.infn.it>> wrote:
>> 
>>> Hi MK,
>>> last meeting before holidays I presented the corrections necessary for photons, for both MC and data. For MC, the reconstructed photon energy is affected by a major shift with respect to the generated one - much larger than what happens for real data. I remember you pointed out that this may be due to a non correct parametrization of the EC sampling fraction in the MC chain (gsim + gpp + a1c). For data, this effect is not present, since the difference between the measured photon energy and the “real” one (as obtained from the kin. fit of gamma p -> p pi0 -> p e+ e- (gamma)) is much smaller.
>>> Therefore, I suspect this effect is related to an error in gsim or gpp rather than a1c, or that different reconstruction routines are used in a1c for data and MC.
>>> 
>>> Can you comment more on this?
>>> 
>>> Thanks
>>> Bests,
>>> Andrea
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