Re: BB vertex vs MRS tracks

From: Stephen J. Sanders (ssanders@ku.edu)
Date: Wed Oct 24 2001 - 15:14:50 EDT

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    Djamel,  Thanks. It is strange that the calibration changes like this.  
    This may be completely off-mark, but I once encountered something similar
    to this where the problem was eventually traced back to the building
    air-conditioning turning on and off.  With standard RG58 cabling
    the signal propagation speed has a fairly large temperature dependence.
    However, in this case I would expect to see a diurnal dependence.
    
    ...steve
    
    Djamel Ouerdane wrote:
    
    >On Wed, 24 Oct 2001, Stephen J. Sanders wrote:
    >
    >>Hi Djamel,
    >>Nice figures.   A question, however:   If I download the latest brag and 
    >>use it with the
    >>run 5326 calibration, does your last figure indicate that I will have to 
    >>apply an
    >>additional offset of 18.07 cm to get the correct BB vertex?
    >>
    >>...steve
    >>
    >
    >Hi Steve, 
    >
    >yes, you're absolutely right. In fact, there will be soon a vertex 
    >calibration package inserting offsets in the database for BB ZDC and so 
    >on. I realized (and Flemming wonders about it) that this offset 
    >fluctuates. It needs some calibration every week at least. It's on its 
    >way...
    >
    >Note that you have to be aware that this offset only applies for the small 
    >tubes. But the efficiency in the small tube vertex finding is very 
    >good (around 0.97 in the sample I've scanned BEFORE requiring MRS tracks).
    >
    >Ciao
    >Djam
    >
    



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