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Twist correction notes, pp2009 (FF)

Updated on Fri, 2009-10-30 14:08. Originally created by andrewar on 2009-10-30 13:32.

 Data for the FullField twist correction was provided by Gene over the weekend:

 

 

Hi, Andrew.

In addition to the 92k events for RFF found at the location below, there are 98k events available for FF at:

/star/institutions/bnl/genevb/FOR_TWIST_FF/*.event.root

If it's of any help, StMagUtilities reports the following "used" values of twist...

FF:
StMagUtilities::XTWIST = -0.31 mrad
StMagUtilities::YTWIST = 0.06 mrad

RFF:
StMagUtilities::XTWIST = -0.599 mrad
StMagUtilities::YTWIST = 0.227 mrad

The database stores PhiXZ equal to the above reported XTWIST, while PhiYZ is the negative of the above reported YTWIST.

Thanks,
-Gene

 

 

 

 

The values of the x,y intercept & slope derived from the refitter are:

X Intercept
    VALUE ERROR
East Intercept 2.975233e-01 5.468941e-03
Slope 1.470253e-03 3.382950e-04
West Intercept 3.105970e-01 6.660565e-03
Slope 1.674960e-03 3.510243e-04
Y Intercept
    VALUE ERROR
East Intercept -2.775844e-02 4.709134e-03
Slope 5.373436e-04 3.023246e-04
West Intercept -2.550180e-02 6.562733e-03
Slope 1.239693e-03 5.029378e-04
 
 
 
So, the y intercepts are ~30um different, with ~60um error. We would need more statistics to get a better measurement, but the current values are within spec (50um). The X intercepts are ~130um different.

 

 




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