[G12] Fwd: Meeting reminder

[Michael C. Kunkel]

Greetings Andrea,

It seems that I did not get this email even though you cc'd g12.. Thank 
you Lei for forwarding it.
I have a few questions about the fitted lines. Are the representations 
derived from a projection plot or fitted to the 2D spectrum?
Also, about the phi corrections, this shape looks very familiar. Could 
you do the trivial task of applying the g12 momentum corrections then 
comparing the phi of the photon before and after? As a refresher to the 
rest of g12, the momentum corrections were basically a phi correction, 
see the write-up.

Otherwise, I am glad that the lepton parameters of the fitter worked. I 
was not able to track down why the pion parameters didn't, as the fitter 
still works well for me.

BR
MK
----------------------------------------
Michael C. Kunkel, PhD
Forschungszentrum Jülich
Nuclear Physics Institute and Juelich Center for Hadron Physics
Experimental Hadron Structure (IKP-1)
www.fz-juelich.de/ikp

On 12/19/18 4:20 PM, lguo wrote:
>
>
>> Begin forwarded message:
>>
>> *From: *Andrea Celentano <andrea.celentano at ge.infn.it 
>> <mailto:andrea.celentano at ge.infn.it>>
>> *Subject: **Re: [G12] Meeting reminder*
>> *Date: *December 19, 2018 at 4:39:29 AM EST
>> *To: *lguo <lguo at jlab.org <mailto:lguo at jlab.org>>
>> *Cc: *g12 <g12 at jlab.org <mailto:g12 at jlab.org>>
>>
>>
> Dear G12,
> I’ll be on a train starting from 10AM JLAB time, hence I don’t know if 
> I’ll be able to join the meeting - will try, but I don’t know about 
> the quality of internet connection via phone.
>
> Concerning meeting time next year, these are my options:
>
> Monday: from 8 AM to 12 AM
> Tuesday: from 8 AM to 12 AM
> Wednsday: from 8 AM to 11.30 AM
> Thursday: from 8 AM to 11 AM
> Friday: from 8 AM to 11 AM
>
> Concerning g12 photons, I realized that is not trivial to isolate in 
> the dataset a clean sample of gamma p -> p pi+ pi- gamma events. I was 
> relying on kin. fit to do so (as done by D. Keller for his g11 
> corrections), selecting events with an high (>15%) CL for the gamma p 
> -> p pi+ pi- (gamma) hypothesis and a low (<1%) CL for the missing pi0 
> hypothesis. However, when comparing the measured gamma with the 
> kin.fit missing gamma, I saw very broad distributions.
>
> Therefore, I tried to repeat the procedure on the reaction gamma p -> 
> pi pi0 -> p e+ e- gamma. I used the same skim as before, assigning to 
> pi+ the e+ mass and to pi- the e- mass and correcting the energy (not 
> the momentum), as suggested by MK. I saw a clean pi0 peak in the 
> missing mass on the proton, and I selected events by applying a 2C 
> kin. fit on the gamma p -> pi e+ e- (gamma) hypothesis, constraining 
> the e+ e- gamma to form a pi0.e
>
> After doing so, I was able to select a very clean set of events. The 
> pulls and the chi2 prob. distribution look fine. I am now in the 
> process of deriving the corrections. I attach a screenshot showing the 
> difference between missing photon energy/angles minus measured photon 
> energy/angles as a function of the missing photon quantities.
>
> Bests,
> Andrea

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