Re: "nan" in the energy of the DBCALPhoton

[Alexander Somov <somov@jlab.org>]

Hi Blake,

Thanks a lot for your prompt reply; I will check and
tell you if i find anything fishy.

Cheers,
        Alex


On Thu, 2 Jul 2009, Blake Leverington wrote:

> Hi Alex,
>
> I've updated the DBCALPhoton_factory.cc file and checked it in with better 
> correction parameters and functions that should avoid any negative values in 
> the base for pow. There shouldn't be any nan values now.  If there is still a 
> problem, let me know. (I think I've checked it in properly anyway.)
>
> -Blake
>
> Blake Leverington wrote:
>> Hi Alex,
>> 
>> I'll look at this today.
>> 
>> -Blake
>> 
>> Alexander Somov wrote:
>>> 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
>>>>> 
>>>> 
>>> 
>>> 
>> 
>