[G12] Target Position

[Carlos Salgado]

Volker et al

I agree with you that we can not correct zero acceptance regions. (This is similar to correct the missing corners of the x:y plots from Chris and Andres).
and we will have to live with that uncertainty (systematic) and just consider the  regions of non-zero acceptance. In cross-sections,  this will introduce a large uncertainty at low energies.

Just to remind everyone, g12 was proposed (and running conditions chosen) to look for diffractive produced (forward) mesons (exotics) at beam energies > 4.4 GeV.

-Carlos

On Jul 12, 2016, at 3:25 PM, Volker Crede wrote:

> For the ω channel, Zulkaida found that we are loosing almost the full c.m. backward region of the charged pions if the reaction happens along the first few centimeters of the photon interacting with the target. This intensity of the cross section is essentially lost when we integrate over these zero-acceptance regions. And this introduces the large uncertainty. 
> 
> We found the effect for pππ (missing π) but it is likely happening as well for pππ (missing η). The effect may be reduced at high energies. And g11a does not show these zero-acceptance holes since the target was centered. 
> 
> - Volker
> 
> 
> On Jul 12, 2016, at 2:29 PM, "Michael C. Kunkel" <mkunkel at jlab.org> wrote:
> 
>> Greetings,
>> 
>> The efficiency map is binned in z, p, theta and phi. However, Volker is correct about the zero acceptance regions postulate.
>> 
>> 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 7/12/16 8:21 PM, Volker Crede wrote:
>>> 
>>> However, it does not solve the acceptance problem when it comes to reconstructing a meson from its decay products. The best efficiency map does not know the physics in zero-acceptance regions.
>> 
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> 
> 
> 
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