Re: BCAL time resolution update

[Alex Dzierba <dzierba@indiana.edu>]

Hi Blake

Here are the cuts/procedure I follow:

- require events with one beam photon in the 580-610 ns time window
- |(ecal-ebeam)/ebeam | < 0.5

To do the time-walk correction for N and S PMTs for segment 8 I
use N PMT-segement 7 as time reference.  I fit the TDC vs ADC
for 8N and 8S - find the parameters for the exponential correction -
apply it to 8N and 8S  and then take the difference times 1/2 and fit
the distribution for 10 bins in beam energy.

As you can see - the fit looks good.    I followed this exact same
procedure for the two version of Run2334 - the data file generated
in Dec 2006 and the one generated on Sunday.  The results using
the earlier files was shown here:
http://dustbunny.physics.indiana.edu/~dzierba/ARDGlueX/BCAL/

BTW - the two-band structure observed for TDC vs ADC when
using the beam time as reference, persists in the new data file
as well.

Cheers
Alex



At 5:20 PM -0600 2/18/08, Blake Leverington wrote:
>Hi Alex,
>
>I assume all the cuts you made are the same. Does anyone have any 
>idea what would have changed or is different in the data file to 
>give you a better 1/sqrt(E) fit? I had to make some ssignificant 
>cuts on the ADC to get a fit like that otherwise it follows 1/E.
>
>-Blake
>
>Alex Dzierba wrote:
>>Hi All
>>
>>David Lawrence created a new data file for me for Run 2334.
>>Attached is the time resolution as a function of energy based
>>on 0.5*(N-S time difference) for segment 8 after time-walk
>>correction.  I don't know what changes were made in the
>>new data file - but I now get a good fit to the conventional
>>resolution dependence on energy.  Recall the the expected
>>contribution to the floor term from beam width should be 32 ps.
>>
>>Will pursue - have to catch my flight.
>>
>>Alex
>>
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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alex R. Dzierba
Chancellor's Professor of Physics (Emeritus)
Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
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Jefferson Lab / 12000 Jefferson Ave / Newport News, VA 23606 / 757-269-7577
Home Phone: 812-825-4063  Cell:  812-327-1881  Fax: 866-541-1263
http://www.dzre.com/alex
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