[Halld-cal] BCAL segmentation

[David Lawrence]

That sounds much better than what Eugene said it meant!

Sorry for the typo Irina. I'll try and be more careful in the future!

-David

On 4/4/11 1:35 PM, George Lolos wrote:
> 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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