Hi Chi,
I would like to offer the program, HoldField_BiotSavart.h, for the
holding field map. I already sent it to everybody but it is most likely
ignored by everybody because of my lack of explanations. I may be able
to give you people the more comprehensive explanations of the mapping
method and the theory next week's analysis meeting. For the moment,
please bear with me with just one of the results, x=y=z=0.ps, which is
the curves obtained after the global fit to the Karen's data of two
dimensions.
The program set, HoldField_BiotSavart.h and HoldCoil_BiotSavart.h, gives
most comprehensive semi-theoretical magnetic field, which should be fast
enough for the charged-particle trajectory tracing for the wire chamber
calibration and GEANT Monte calro simulation as well as the target
polarization angles. For the moment, it predicts the measured field
within 30 G, but for most cases the errors are much smaller. There
should not be too long before the final version is released. The files
are located at /scratch/bud18/shino.
Thank you,
Aki
Chi Zhang wrote:
>Hi Boss, will the lunch be provided? :)
>
>seriously, the things I got asked about this morning at meeting.
>
>1. in terms of the errors between 32 and 45 deg runs. turns out with 45(or
>47 or whatever in that neighborhood), errors on T20 are only marginally
>better than with 32 deg. we are talking about +-0.15 vs +-0.14 type of
>difference.
>
>2. in terms of spin angle error, I guess I was too conservative seeing the
>pre July data with low polarization and bad tracking and stuff. Boy
>those data are a misery to look at.
>
>With current Pzz (>~0.6), with same counts as we collected from July to
>Oct, I believe now average spin angle can be measured by T20 to +-0.5~0.6
>degrees.
>
>Another method to esitmate this error, proposed by Genya, is also used to
>check this estimation. it gives a bit more optimistic estimation, arround
>0.4 deg. But in the spirit of Murphy's law, which I now firmly believe is
>as true as the 2nd law of thermal dynamics, I tend to believe even +-0.5
>is a rather optimistic estimation. :)
>
>3. a spin angle profile as seen by ed elastic. please see the attatched
>plot. the black curve is the "scaled to 32 deg" profile. It takes the 47
>degree profile, scaled the tangent of angle at any point by
>tan(32)/tan(47). the purple data points are spin angle measured from ed
>elastic by cutting the target length into intervals. the division of the
>-20 to 20cm range is such that each interval contains roughly equal
>counts. data seem to want to dip more. I say we should let a actual survey
>speak.
>
>To beat on actual survey, I still believe the field mapping is THE right
>way to control spin angle. T20 measurement or whatever measurement from data
>should be taken only to monitor and/or confirm the survey result and to
>make sure that problems would be quickly spotted if there were any
>problems, such as a shorted coil, which motivated the T20 spin angle
>measurement ealier in 2004 anyway.
>
>About the event by event correction of spin angle. it is done in ed
>elasitc channel with the "fudged" angle profile. All the programs and
>infrastructures are constructed months ago, the one single missing
>piece is the map.
>
>Chi
>
>On Wed, 19 Jan 2005, Tancredi Botto wrote:
>
>
>
>>Following today's discussion I suggest an agenda for our meeting with
>>D. Philips next week, assuming we have regular blast meeting at 9.00.
>>
>>Maybe D. Philips talk could be anticipated to 13.30 to suit Richard
>>travel needs. Let me know what you think.
>>
>>
>>10.30 AM: Overview BLAST detector, BLAST spin dependent eep asymmetries vs
>> pmiss
>>10.45 VZ: GEn measurament
>>
>>11.00 CZ: BLAST T20 measurament, and discussion of its normalization
>>
>>12.00 Lunch (Bates library)
>>
>>14.00 D. Philips talk
>>
>>15.00 General discussion
>>
>>--
>>________________________________________________________________________________
>>Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
>>research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
>>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>
>>
>>
>>
>
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