[Halld-offline] Gluex event sizes in pythia MC

[David Lawrence]

Hi Richard,

     Do your numbers for the FDC filter out the "truth" values buried in 
the forwardDC structure? When I look at the XML definition for the HDDM 
file I see this:

<forwardDC minOccurs="0">
<fdcChamber layer="int" maxOccurs="unbounded" module="int">
<fdcAnodeWire maxOccurs="unbounded" minOccurs="0" wire="int">
<fdcAnodeHit dE="float" maxOccurs="unbounded" t="float" itrack="int" 
ptype="int"/>
<fdcAnodeTruthHit dE="float" maxOccurs="unbounded" t="float" d="float" 
itrack="int" ptype="int"/>
</fdcAnodeWire>
<fdcCathodeStrip maxOccurs="unbounded" minOccurs="0" plane="int" 
strip="int">
<fdcCathodeHit maxOccurs="unbounded" q="float" t="float" itrack="int" 
ptype="int"/>
<fdcCathodeTruthHit maxOccurs="unbounded" q="float" t="float" 
itrack="int" ptype="int"/>
</fdcCathodeStrip>
<fdcTruthPoint E="float" dEdx="float" dradius="float" 
maxOccurs="unbounded" minOccurs="0" primary="boolean" ptype="int" 
px="float" py="float" pz="float" t="float" track="int" x="float" 
y="float" z="float"/>
</fdcChamber>
</forwardDC>

The fdcAnodeTruthHit and fdcCathodeTruthHit will not be in the raw data 
set. Also, if you used a more recent version of the data model (post 
Sept. 28) then the the itrack and ptype fields in the fdcAnodeHit and 
fdcCathodeHit structures are also there which won't be in the raw data. 
If both of these are the case, then you're counting 12 words per hit as 
opposed to 4 for the raw data. If only the first is true, then you may 
be counting 8 words as opposed to 4 for the raw data. I only ask because 
you break down the CDC into hits, truth hits and truth points, but I 
don't see that for the FDC.

Regards,
-Dave

On 10/27/10 1:00 PM, Heyes Graham wrote:
> Richard,
> 	thanks for the quick reply. I have had the response from various people at various times that trigger thresholds would be set to keep event sizes and rates within limits. What isn't clear is if the rates and sizes have changed significantly since they were guestimated several years ago.
>
> The last sentence of your email is a question aimed ad Matt who isn't on the recipients list of the email.
>
> 	Regards,
> 		Graham
>
> On Oct 27, 2010, at 11:09 am, Richard Jones wrote:
>
>> Graham and all,
>>
>> We do not have a number on the encoding ratio between coda and hddm, but I believe that the two should be within 30% of each other for the identical set of hits being recorded.  The big effect -- we are looking at a factor 3.5 -- lies in the thresholds that are used to define what gets called a hit.  Matt points out that these thresholds are deliberately set artificially low in Monte Carlo so that we can add fluctuations later.  A better estimate for event sizes might be obtained by looking at the events coming out of mcsmear, after applying more realistic hit thresholds to those events to see what we get.
>>
>> Matt, do we have the necessary information about what those thresholds should be in order to allow me to carry out this exercise?
>>
>> -Richard J.
>>