[G12] Target Position

[Michael Paolone]

Continuing on the same train of thought:  there are also many methods to
interpolate or extrapolate across "holes" in kinematic variables, from
simple splines to more complicated multi-dimensional machine learning
techniques.  Unfortunately, there will always be a systematic uncertainty
cost that is technique dependent, but it is something to consider.

-Michael

> 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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