[d2n-analysis-talk] BPM Calibration Discrepancy: BigBite vs LHRS

[Brad Sawatzky]

Hi Diana,

I think Vince is right -- it is probably a pedestal difference.  If you
can find a BPM pedestal, then you're good to go.  Otherwise you have to
repeat the calibration procedure for the LHRS.  (The pedestal just gives
you an extra point in the fit -- it isn't really critical.)

-- Brad

On Thu, 08 Apr 2010, Vincent Sulkosky wrote:

> My first guess is that the BPM pedestals between the left HRS and BB arms 
> are different.  This can definitely be the case, since we are using two 
> separate sets of electronics.  We typically do a BPM pedestal run at some 
> point early in the runb.  If it exists you should find it and analyze the 
> data to get the BPM pedestals for the BB database.  On the other hand, 
> Bodo's web page says it is not necessary and the pedestals can be taken 
> out in the fits.
> 
> I suspect this is what has caused the difference.  The important question 
> is do the beam positions from BB and the Left HRS agree after calibration?
> 
> Best Regards,
> Vince
> 
-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov