[Clas_hadron] Fwd: Re: Users meeting presentation( with the attachment)

[Philip L. Cole]

Hi all,

Olga cannot access the clas_hadron distribution site.  I will reply for her.
Just to clarify, this in NOT a Fermi-momentum effect. This was a detector
effect over the neutral tracks.

Regards,
Phil


From: Olga Cortes Becerra <omcortes at email.gwu.edu>
Sent: Tuesday, June 25, 2019 10:41:44 AM
To: andrea.celentano at ge.infn.it; Marco Battaglieri
Cc: Philip L Cole
Subject: [EXTERNAL] Answer to Andrea's question

Dear Andrea,

Yes, you are right! in principle it should not have any dependency (at
least this is what we expected). The short answer would be that we were
able to reproduce this effect with a Toy MC.

 How I worked in it was:
1. For the deuteron target : we assigned randomly the momentum to the
neutron with a “fermi momentum” distribution. The proton target 4p was
obtained taking the difference between the four momentum of the deuteron
at rest minus this on-shell neutron 4p. The proton target then is
off-shell. (i forgot the name of the model used for the fermi momentum but
I can check it out for you)
2. Only a phase space data with a simple t-slope was used
3. Only signal events were generated
4. To simulate the detector response, we used  real data resolution from
g13b run period to smear our positive charged particles, and a nominal
resolution of the EC to smear the neutral particles.

If I check the invariant mass of the two photons as a function of the
missing mass( the pi0), we also get a slope. That was also reproduced.

Best regards,

Olga

> Hi Phil,
> I agree with you. However, what I do not understand is why the omega
> "band" is diagonal in the plot, i.e. there is a kinematic dependence on
> the missing mass of the system. It may be a nuclear effect (I am not
> expert on this), or something else.
> If the experiment was performed on a lH2 target, the omega mass seen as
> the pi+ pi- pi0 invariant mass, would not depend at all on the missing
> mass on this system.
>
> Bests,
> Andrea
>
> On 6/25/19 1:50 PM, Philip L. Cole wrote:
>>
>> Hi Andrea,
>>
>> In the charged decay mode, the eta can decay 28% percent of the time
>> into
>> pi+ pi- pi0
>>
>> Given the selection criteria, Olga is sensitive to the this three-pion
>> decay mode.  And the eta pops up as well.
>>
>> Regards,
>> Phil
>>
>>> Hi Marco,
>>> thanks for your email. I have a comment regarding slide n. 10: why is
>>> the
>>> omega signal (and the eta signal), intended as the invariant mass of
>>> the
>>> Pi+ Pi- Pi0 system, depending on the missing mass on this system? Is
>>> this
>>> a nuclear effect?
>>>
>>> Thanks
>>> Andrea
>>>
>>>> On Jun 24, 2019, at 15:28, Marco Battaglieri <battaglieri at ge.infn.it>
>>>> wrote:
>>>>
>>>> Dear hadronists,
>>>> please have a look to Olga's talk intended to be presented at the User
>>>> Group and let us have (asap!) your comments/edits
>>>> Cheers
>>>> Marco
>>>> <Re: Users meeting presentation( with the
>>>> attachment).eml>_______________________________________________
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>
>
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-- 
   Philip L. Cole
   Professor and Chair
   Lamar University
   Department of Physics
   Beaumont, Texas 77710

   (409) 880-8292  office
            -8245  fax
    pcole at lamar.edu