Re: "nan" in the energy of the DBCALPhoton

[Alexander Somov <somov@jlab.org>]

Hi Matt,

Thanks for the prompt reply and explanations.
Blake, could you please take a look on this
reconstruction feature.

Thanks,
        Alex


On Tue, 30 Jun 2009, Matthew Shepherd wrote:

>
> Hi Alex,
>
> This particular section of code was added by Blake recently to try to improve 
> reconstruction at the end of the module.  I'm not familiar with it -- Blake, 
> can you help Alex?
>
> Indeed it looks like the problem is trying to call pow with a negative base. 
> That will certainly generate nan.
>
> -Matt
>
> On Jun 30, 2009, at 5:04 PM, Alexander Somov wrote:
>
>> 
>> Hi Matt,
>> 
>> I have found a few events in the BCAL reconstruction
>> where the photon energy is not calculated properly.
>> Below is a typical example:
>> 
>> DBCALPhoton:
>>     x:      y:      z:    px:    py:    pz:     E:
>> ----------------------------------------------------
>> 56.62   37.97  133.08   0.12   0.08   0.15   0.21
>> -9.08   67.51  211.40  -0.06   0.46   1.01   1.11
>> -64.92   23.81  306.27  -0.45   0.16   1.67   1.74
>> 19.78  -62.68  405.37    nan    nan    nan    nan    <---
>> 61.69  -31.96  397.37   0.01  -0.00   0.05   0.05
>> 
>> DBCALShower:
>>     x:      y:      z:     t:     E:
>> --------------------------------------
>> 56.62   37.97  133.08   6.11   0.18
>> -9.08   67.51  211.40   5.40   1.04
>> -64.92   23.81  306.27   8.38   1.61
>> 19.78  -62.68  405.37  11.77   0.51    <---
>> 61.69  -31.96  397.37  12.55   0.03
>> 
>> The problem appears at the  edge of the BCAL, specifically
>> in the DBCALPhoton_factory.cc file where the energy of a
>> photon  is calculated (for zEntry >= 370.0 ):
>> 
>> double energy = pow( ((**showItr).E - lin ) / scale, 1 / ( 1 + nonlin ) );
>> lin    -0.08144
>> nonlin -0.616129
>> scale  -0.0563619
>> **showItr 0.505658  (shower energy)
>> energy nan
>> 
>> pow(x,y) is called here with the negative x.
>> 
>> Could you please check the callibration coefficients in the 
>> DBCALPhoton_factory.cc
>> factory (I have no clue how these coefficients have been obtained). I would 
>> like to finish  with the acceptance studies shortly.
>> 
>> Thanks,
>>      Sascha
>> 
>> 
>> P.S. Just in case, I put the hddm file with  "p eta pi0 pi0" events
>> where i have observed the problem to  ~/public_html/debug.hddm
>> 
>