Re: single end hits

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Tue, 30 Dec 2008, Matthew Shepherd wrote:

Dear Blake,

taking care about the single its is of course very important and Matt has 
already explained how to do this. What I would like to see is also a study 
under which circumstances we get single hits. Of course on reason is 
detection inefficencies, but I would assume an other one is photons 
hitting very very close to one end of the BCal, so the other sight sees 
ight after 4m of fibers.

Thanks and Happy new year
elke


> Date: Tue, 30 Dec 2008 17:53:01 -0500
> From: Matthew Shepherd <mashephe@indiana.edu>
> To: Blake Leverington <leverinb@uregina.ca>
> Cc: GlueX Software <halld-offline@jlab.org>,
>     Hall-D Calorimetry <halld-cal@jlab.org>
> Subject: Re: single end hits
> 
>
> Hi Blake,
>
> I imagine the reason it was not done before is because it is not possible to 
> calculate z and t.  This causes problems also since (I believe) the 
> reconstruction corrects for attenuation on the cell level not on the full 
> cluster level.  Furthermore, I suspect with the KLOE geometry there was no 
> strong motivation to try to improve it.
>
> You may be able to do this leaving the main hunk of the KLOE reconstruction 
> code (which has some confusing data structures) fairly unchanged.  There is 
> an initial loop in the beginning the prunes out all the single ended hits. 
> You just need to stuff them somewhere and then make a loop at the end that 
> tries to put them back onto the lists of clusters.  You can use the cluster z 
> position to correct the energy of the single ended hit.
>
> The first step would be just to try to enhance the performance by adding 
> single hits to existing showers.  In this case DBCALShower_factory produces 
> the same shower list effectively however all the energy values a tweaked a 
> little for the single ended hits.  (You could in principle also adjust the 
> positions, but we know at leading order energy is the most important, and the 
> corrections from single ended hits will be small.)
>
> Of course, with any change to the algorithm you'll need to adjust your 
> calibration.  (You will be explicitly adding back reconstructed energy 
> instead of estimating the energy lost using some calibration constant.)
>
> I expect incorporation of single ended hits to only make a difference at low 
> energy near the end of the BCAL.  It will help to rescue the resolution for 
> those 200 MeV photons in the end of the BCAL.  We know this is the "magic 
> region," but you might want to evaluate maximum potential gain before 
> embarking on this adventure.  Come up with some figure of merit and run some 
> MC with the threshold in the BCAL set very low and the fiber attenuation 
> length set high.  This might give you a minimum number of single ended hits 
> and a "best case scenario."  If the gains are tiny, you might rather spend 
> your time working on some toy amplitude analysis studies!
>
> Cheers,
>
> -Matt
>
>
> On Dec 30, 2008, at 5:06 PM, Blake Leverington wrote:
>
>> Hey all,
>> 
>> So a question before I start trying to implement single ended hits into the 
>> bcal code, is there any reason that there has to be 2-ended hits such as 
>> some catastrophic error or is it just that a few things aren't able to be 
>> calculated for those hits, such as z and t or just need to be calculated 
>> differently, like e? I'm referring to the variables in DBCALShower_factory. 
>> I have a general idea how to go about this, and it seems fairly simple, but 
>> I was just checking to make sure there isn't anything down the line that 
>> will be affected that people are aware of.
>> 
>> -Blake
>

  ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
   )    `\                                                  -
  /    '. |                                                  +
  |       `,              Elke-Caroline Aschenauer            =
   \,_  `-/                                                    -
   ,&&&&&V         Jefferson Lab                                +
  ,&&&&&&&&:       HALL-D 12C / F381       121-A Atlantic Avenue =
,&&&&&&&&&&;      Suite 8                 Hampton, VA 23664      -
|  |&&&&&&&;\     12000 Jefferson Ave                             +
|  |       :_) _  Newport News, VA 23606  Tel.:  001-757-224-1216  =
|  |       ;--' | Mail:  elke@jlab.org    Mobil: 001-757-256-5224   -
'--'   `-.--.   |                                                    +
    \_    |  |---' Tel.:  001-757-269-5352                             =
      `-._\__/     Fax.:  001-757-269-6331                              -
             +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+