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Hi Andrea:
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<div>Can you do a test *without* including gpp? This might help isolate the cause of the issue.</div>
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<div>John<br>
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<div>John W. Price</div>
<div>Professor, CSUDH Department of Physics</div>
<div>Coordinator, Science, Mathematics, and Technology Program</div>
<div>310-243-3403</div>
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On Jan 16, 2019, at 05:15, Michael Kunkel <<a href="mailto:mkunkel@jlab.org">mkunkel@jlab.org</a>> wrote:<br>
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<div dir="ltr">Greetings Andrea,
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<div>I believe you just verified what Diane Schott and I had been trying to convince other of for many years. :)</div>
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<div>However, the correction for simulation is quite trivial since we already know the generated 4vector. </div>
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<div>I don’t believe the kinfit package handles this problem.<br>
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<div style="direction: inherit;"><span style="background-color: rgba(255, 255, 255, 0);">BR<br>
MK <br>
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Michael C. Kunkel, USMC, PhD<br>
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On Jan 16, 2019, at 05:59, Andrea Celentano <<a href="mailto:andrea.celentano@ge.infn.it">andrea.celentano@ge.infn.it</a>> wrote:<br>
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<div dir="ltr"><span>Hi MK,</span><br>
<span>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.</span><br>
<span>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.</span><br>
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<span>Can you comment more on this?</span><br>
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<span>Thanks</span><br>
<span>Bests,</span><br>
<span>Andrea</span></div>
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