[Halld-cal] BCAL segmentation

[George Lolos]

The ancient Greek name, which also the modern Greek, is Irini (mean  
peace), so we know what we're talking about here... :-)

George
On 3-Apr-11, at 7:51 PM, semenov at jlab.org wrote:

> David:
>
> 2 comments:
>
> 1. Irina's name is "Irina" and not some other ancient-Greek versions  
> (with
> all my respect to the Greek culture :)
>
> 2. About to use the fitting function instead calculating RMS: I do  
> agree
> that the fitting procedure (with Breit-Wigner convoluted with  
> Gaussian or
> just sum of 2 Gaussians or Gaussian core and some tails) will  
> provide more
> stable result; but we need agreement about what value to use as the
> numerical estimator of the resolution. If we use "1-sigma" analog  
> (viz.,
> sixty-something percent confidence interval), we will catch the "core"
> structure only and will not be sensitive much to the tails, and  
> definitely
> we don't want to do such a thing. I do believe that 95%-confidence
> interval will be much more appropriate, but we all should be aware  
> that it
> corresponds to "2-sigma-resolution" if we will make any comparisons  
> with
> the "1-sigma" resolutions from Gaussian-shaped spectra.
>
> So, do we all agree to use from now the 95%-confidence interval as the
> resolution?
>
> Thank you,
> Andrei
>
>
>
>
>
>
>
>> Hi Irinia,
>>
>>     Please find my responses below.
>>
>> On 3/31/11 9:20 PM, stepi at jlab.org wrote:
>>> Hi David,
>>>
>>> plots on the 2nd slide were calculated for the range of z  from  
>>> -34cm to
>>> 30 cm (Near part of BCal).
>> OK. This would make things seem more consistent. Your plots looked
>> similar to my ~90 degree plot which I believe corresponds to z=0 in  
>> your
>> coordinate system.
>>
>>> For the RMS calculation I used the same method : TH1D :: GetRMS().
>>> For the histogram presented on this slide limits for RMS are:
>>> (-15 to 15)  for the histogram "Fine-Segmented" and
>>> (-30 to 30)  for the histogram "Summed-in-Towers".
>>>
>> Looking at the documentation for TH1, it looks like we should be  
>> calling
>> TH1::StatOverflows() prior to filling the histogram if we want the  
>> RMS
>> to include the tails. I did not do this myself, but will correct  
>> that.
>> If that is not done, then the RMS will be a (possibly strong)  
>> function
>> of the histogram limits.
>>
>>> For the comparison consistency :
>>> All these results ( energy resolution, polar angle and azimuthal  
>>> angle)
>>> were obtained under the following conditions:
>>> ( "nTrue == 1&&  prim == 1&&  nShow == 1" )
>>> that were created as:
>>> ......
>>>    m_rootTree->Branch( "nTrue",&m_nTrue, "nTrue/I" );
>>>    m_rootTree->Branch( "prim", m_primary, "prim[nTrue]/F" );
>>>    m_rootTree->Branch( "nShow",&m_numShowers, "nShow/I" );
>>>
>>> I have few questions to you:
>>>
>> OK, that may explain part of the discrepancy. In my RMS plot I'm not
>> cutting on having only 1 reconstructed shower and I have no cut to
>> ensure the primary particle makes it to the BCAL. My events will
>> therefore, not be as clean so the tails will be a little larger which
>> would blow up my RMS.
>>
>>> 1. You didn't put the numbers for the RMS on your plots. It's good  
>>> to
>>> know
>>> how big the difference really is.
>>>
>> I can do this, but I don't trust the RMS as a good indicator since  
>> it is
>> so sensitive to the tails. I think we we need to find an appropriate
>> fitting function.
>>
>>> 2. What version of reconstruction code did you use? As I mentioned
>>> before,
>>> I am using tag version sim-recon-2011-02-02 . Matt recently found  
>>> the
>>> bug
>>> in the smear.cc that included in this release.
>>> To fix this bug,  the opening lines of SmearBCal should be changed  
>>> to:
>>> ......
>>>   for( int m = 1; m<= 48; ++m ){
>>>     for( int l = 1; l<= 10; ++l ){
>>>       for( int s = 1; s<= 4; ++s ){
>>> ............
>>> (the l and s loop limits were swapped).
>>> For the plots presented on the meeting, the "bagged" version was  
>>> used.
>>> After fixing the bug, the change in the angle and the energy  
>>> resolutions
>>> is not big.
>>>
>> I used revision 7602 from the repository which looks to still have  
>> the
>> bug. I'll fix that as well.
>>
>>
>> Regards,
>> -Dave
>>
>>
>>> Thank you,
>>> Irina
>>>
>>>> Hi Andrei and Irina,
>>>>
>>>>      I've start trying to look at the splitoffs issue for the  
>>>> course
>>>> vs.
>>>> finely segmented readout options in the BCAL. One of my first  
>>>> steps was
>>>> to try and compare resolutions to some plots you showed at the  
>>>> meeting
>>>> this week as a check that I've got the course segmentation set up
>>>> correctly. I've not gotten results that seem completely  
>>>> consistent with
>>>> yours. I'd like find the source of the discrepancy. I've put a  
>>>> couple
>>>> of
>>>> the plots into a PDF that I uploaded to the wiki here:
>>>>
>>>> http://www.jlab.org/Hall-D/software/wiki/images/7/7f/20110405_bcal_segmentation.pdf
>>>>
>>>> My first question is if the resolution plots shown on your 2nd  
>>>> slide
>>>> were for the full range of z or, just for some range around 90  
>>>> degrees.
>>>>
>>>> Also, how did you calculate the RMS? In my plots, I just used  
>>>> ROOT's
>>>> TH1D::GetRMS() method which I believe is limited by the defined
>>>> histogram range (-20 to +20 in my case). I would think that by  
>>>> cutting
>>>> off the tails, I would get a *smaller* RMS than the actual, but  
>>>> mine
>>>> seems bigger than yours. Any clues as to why?
>>>>
>>>> Regards,
>>>> -David
>>>>
>>
>
>
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