[Clas12_verystrange] [EXTERNAL] Electron energy correction

[Geraint Clash]

As requested the beam energy used for these corrections was 10.6041 GeV.

Thanks,
Geraint Clash.

On Wed, 15 Apr 2020 at 17:56, Geraint Clash <geraintclash at gmail.com> wrote:

> Hello all,
>
> I have re-done the energy correction I shared with you previously but
> using pass 1 data from this path:
> /volatile/clas12/users/devita/2pi/rga-pass1v0/skim3/. I have used the
> following function to produce the attached plots:
>
> TLorentzVector  Correct_Electron(TLorentzVector x){
>
>   Double_t E_new, Px_el, Py_el, Pz_el;
>   TLorentzVector el_new;
>
>   E_new =
> x.E()-0.03689+0.1412*x.E()-0.04316*pow(x.E(),2)+0.007046*pow(x.E(),3)-0.0004055*pow(x.E(),4);
>
>   Px_el = E_new*(x.Px()/x.Rho());
>   Py_el = E_new*(x.Py()/x.Rho());
>   Pz_el = E_new*(x.Pz()/x.Rho());
>
>   el_new.SetXYZM(Px_el, Py_el, Pz_el, 0.000511);
>
>   return el_new;
> }
>
> then calling the function like this  Correct_Electron(measured electron
> TLorentzVector) and that goes in place of the measured electron
> TLorentzVector.
>
> The attached file is a short presentation containing the following: The
> separate missing mass of everything and the proton plots fitted to show the
> mean and sigma, for both the original and corrected cases. Then the missing
> mass plots unfitted on the same axis where red is the original. Finally,
> the delta energy plots where the corrected is on the left.
>
> Thanks,
> Geraint Clash.
>
> On Wed, 15 Apr 2020 at 15:10, nicholas <nicholas at jlab.org> wrote:
>
>> Hi Will,
>>
>> 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.
>>
>> Cheers,
>> -N
>>
>>
>> On 15 Apr 2020, at 15:00, William Phelps <wphelps at jlab.org> wrote:
>>
>> Hello Geraint,
>>
>> 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?
>>
>> I attached a 2d histogram that might make more sense than what I said in
>> the paragraph above.
>>
>> A secondary question to the group: If the reconstructed momentum is
>> incorrect does this mean that the angle is also incorrect?
>>
>> Thanks,
>> -Will
>>
>> <Plot_04-15-2020_09.53.13_AM.png>
>>
>> On Apr 3, 2020, at 9:58 AM, Geraint Clash <geraintclash at gmail.com> wrote:
>>
>> Hello all,
>>
>> 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.
>> 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).
>>
>> 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.
>>
>> Thanks,
>> Geraint Clash.
>> <Del_E_mean_fit.png><Del_E.png>
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