<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Will, <div class=""><br class=""></div><div class="">We have no indication that the angles are wrong as these are established from the clusters. We understand how the energy is off in the FT and I think at this stage an initial correction that Geraint is working on is sufficient to start looking at things in much more detail. Raffaella came up with a different energy reconstruction, which accounts for some of this difference, but it is not sufficient to correct for it in its entirety. By no means the correction that Geraint will send soon is the final one and he will work on more studies using higher stats. I think the way the correction is determined/applied is not very crucial especially since in your plot there is still a significant slope and it doesnt seem to be a scale factor independent of E.</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">-N</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 15 Apr 2020, at 15:00, William Phelps <<a href="mailto:wphelps@jlab.org" class="">wphelps@jlab.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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Hello Geraint,
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<div class="">I have been thinking about this electron correction (briefly). It seems to me that it would make sense to have the correction as a ratio P_missing/P_reconstructed as a function of P_reconstructed. So all we would need to do is scale the electron
momentum (and recalculate energy). You mentioned that you are going to take another look at your correction during the meeting, is this what you are thinking about doing? </div>
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<div class="">I attached a 2d histogram that might make more sense than what I said in the paragraph above.</div>
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<div class="">A secondary question to the group: If the reconstructed momentum is incorrect does this mean that the angle is also incorrect?</div>
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<div class="">Thanks,</div>
<div class="">-Will</div>
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<div class=""><span id="cid:F253E635-7957-40F7-B576-8A35BD3956D6"><Plot_04-15-2020_09.53.13_AM.png></span><br class="">
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<div class="">On Apr 3, 2020, at 9:58 AM, Geraint Clash <<a href="mailto:geraintclash@gmail.com" class="">geraintclash@gmail.com</a>> wrote:</div>
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<div class="">Hello all,<br class="">
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I carried out a study on the difference between the energy of the electron when you treat it as missing and the measured electron using skim3 data from this path: /volatile/clas12/users/clas12/rich/dst/recon/005038/. For this, the exclusive reaction ep->e’p
pi+pi- was selected, with three-sigma cuts around missing mass squared of all products and the missing mass of the proton.<br class="">
The plot of the difference in energy ("missing" electron - detected electron) against the electron measured energy is the attached file Del_E. Y-projections were fitted with Gaussians and the means were fitted with a fourth-order polynomial establishing the
correction function (see attached).<br class="">
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The energy correction which should be added to the measured electron energy, E, is: -0.0004x^4+0.0071x^3-0.0432x^2+0.1356x-0.0257. <br class="">
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<div class="">Thanks,</div>
<div class="">Geraint Clash.</div>
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<span id="cid:f_k8k8c6dz1" class=""><Del_E_mean_fit.png></span><span id="cid:f_k8k8c6df0" class=""><Del_E.png></span>_______________________________________________<br class="">
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