Re: "nan" in the energy of the DBCALPhoton

[Alexander Somov <somov@jlab.org>]

Could you also commit all your latest changes to trunk
(rather than release-2009-02-24) to be sure that they
will appear in the next lib release.

Thanks,
        Alex


On Fri, 3 Jul 2009, Alexander Somov wrote:

> 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
>>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>> 
>
>