[Frost] tagger sag & phi dependence

[Steffen Strauch]

Dear Sung,

it is very good you looked into this.

It is interesting that the effect is rather independent of the  
particle type (with the proton results offset by 0.5 units in momentum  
pull compared to the pions).  The phi dependence of the pull within  
each sector is almost everywhere quite similar, monotone, and  
decreasing.  It seems that the holding field is not responsible for  
the effect as the results are independent of the particle charge.

Earlier, Michael Dugger pointed out to me Mike Williams' CLAS note  
(CLAS-NOTE 04-017,
http://www1.jlab.org/ul/Physics/Hall-B/clas/public/2004-017.pdf
In this report momentum corrections are discussed and drift chamber  
misalignments are said to be responsible for the effect.

All the best,
Steffen


On Jun 22, 2010, at 3:56 PM, Sungkyun Park wrote:

> Hi Steffen,
>
> To check the phi-dependence in our double-pion data, I make some  
> histograms in the following web:
>
>  http://hadron.physics.fsu.edu/~skpark/research/research_jun2110.html
>
> I make 2D-histogram whose x-axis is the phi angle (LAB) of each  
> particle and y-axis is the momentum pull of each particle and  
> project it to 36 plots. I make the histogram using the mean of the  
> Gaussian fitting.
> I think momentum pulls of each particle have some phi-dependence  
> like your result.
>
> Sung
> Florida State University
>
>> Dear Sung et al.,
>>
>> we may or may not have a tagger-sag problem in g9a. I agree with
>> Michael that it is important to have all 'known' corrections
>> implemented before the kinematic fitter is applied.  The fitter is
>> probably not a good tool to correct for 'systematic' errors.  In
>> terms
>> of these systematic effects I am still very concerned about the
>> azimuthal dependence of the g9a single-pion data.  The variation of
>>
>> the measured pi+ momentum from the expected momentum (assuming
>> correctly measured pion angles and photon energy) is very large; up
>> to
>> 10-15 MeV/c within one sector's coverage.
>>
>> See: http://www.jlab.org/Hall-B/secure/g9/g9_strauch/mtg/20100414.pdf
>>
>> I wonder if you see such a phi-dependence also in your double-pion
>> data or if the many particles in the final state wash out any such
>> effect.  We need to address this phi dependence.
>>
>> All the best,
>> Steffen
>>
>>
>>
>>

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