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Re: BCAL06 note version 1.1




 Hi George,

    I think the 100ps jitter on the means is already accounted for in 
the 113ps intrinsic resolution of the tagger. If you look at Simon's 
entry in the logbook (see 
https://halldweb1.jlab.org/halldlog/loginfo?action=logentry&entryId=199) 
you'll see there is a slight jitter there too. The 160ps width comes 
from the projection of that (see second plot in Simon's entry). The 
113ps (=sqrt(2)*160ps) therefore includes both intrinsic T-counter 
resolution and paddle-to-paddle variation(i.e. calibration). If Blake 
were to project his figure 6 onto the Y-axis and fit it, he should get a 
sigma of *less* than 113ps since the mean should only be measuring the 
paddle-to-paddle jitter contribution to the tagger timing error.

    After discussing this with Simon some, we agreed that if one were we 
to spend time refining the calibration of the tagger, it would reduce 
the 113ps number we are currently using for the intrinsic tagger timing. 
This would improve the BCAL-tagger timing resolution, but since it gets 
subtracted out, the intrinsic BCAL timing resolution would not change.

What do you think?

Regards,
-David

George Lolos wrote:
> Hi Blake:
>
> Reading your second version and after our brief discussion, here are 
> my thoughts:
>
> While the resolution certainly meets the demands for the DOE input, I 
> believe that any further analysis should await the refinement of the 
> tagger OR.  We are now seeing the effects of the fluctuations evident 
> in Figure 6 that can only come from slight timing misalignment among 
> the tagger t-counters.  You mention deviation from the mean of 100 ps 
> and even though this is a small number, it's large enough to affect 
> both the absolute value of the floor term and the combined resolution 
> of say cells 7 and 8 (Richard's comment).  Cell 8 has superior 
> statistics, so all else being equal, it should give better numbers 
> than 7 while we see the opposite.   Also the lack of improvement when 
> they are combined also hints to me that we are bumping against an 
> uncorrected effect.
>
> All in all, good work.
>
> George
>
>
> Blake Leverington wrote:
>
>> Hi all,
>>
>> I've posted the preliminary draft of the note on timing resolution 
>> for the BCal to the wiki. You can find it directly here:
>> http://www.jlab.org/Hall-D/software/wiki/index.php/BCal_Timing_Resolution_Note 
>>
>>
>> I'm going home to sleep now. Send me all your comments or complaints.
>>
>> -Blake
>
>
>

-- 

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