[Halld-offline] Gluex event sizes in pythia MC

[Alexander Somov]

Hi all,

I agree with Matt, noise in the chambers might be a problem
and will increase the event size. We had a discussion some
time ago whether we we should include some noise estimates
to the event size and eventually decided not to do it. Noise
hits in the bcal were also not included (as far as I remember)...

Cheers,
       Sascha



On Wed, 27 Oct 2010, Matthew Shepherd wrote:

>
> Hi all,
>
> A couple of comments:
>
> For the FCAL and BCAL the thresholds are artificially low in hdgeant.  This is because the there are additional random detector effects (e.g. sampling fraction fluctuations, photon statistics, electronics noise) that can cause upward fluctuations in the hit energy and allow particular hits to exceed the threshold.  If the hdgeant threshold is set at the true electronics threshold then there will be no hits just under threshold that have the opportunity to fluctuate upward in mcsmear.  I don't know to what extent this is also true in the CDC and FDC.
>
> Past experience in BES and CLEO says that number of hits, especially in wire chambers, is driven strongly by noise.  With all of those nice conducting antennae in hanging out in front of preamplifiers, it was a real challenge to keep the noise down in the chambers.  (At one point in CLEO we could even see traffic on the control bus for the Silicon detector as hits in the drift chamber!  Accelerator systems were also a problem.)  Maybe this won't be an issue with a photon beam that is far removed from the main accelerator.  However, if the FDC and CDC are really driving the size, which is getting large, we might consider a safety factor for noise.
>
> -Matt
>
> On Oct 27, 2010, at 2:51 AM, Richard Jones wrote:
>
>> Curtis,
>>
>> I have added a histogram of the means to the bottom of the same web page.
>>
>> http://zeus.phys.uconn.edu/halld/hdgeant/sizes-10-2010/
>>
>> As to how much space is saved when hits are stored as ADC/TDC values, I doubt that there is more than a 20% space effect coming from that.  Most of this factor 3.5 increase over Alex's estimate probably comes from the failure to apply realistic thresholds when saving hits in the chambers, particularly the FDC.
>>
>> -Richard J.
>>
>>
>> On 10/26/2010 10:45 PM, Curtis A. Meyer wrote:
>>> Thanks Richard --
>>>
>>>    These look really nice, I believe that they will be quite useful! While I can pull it
>>> out of your plots, I was wondering if you also had a plot that showed the "mean"
>>> for each of the detector systems on a single plot. It looks to me that after the FDC,
>>> the CDC may be the culprit, but I am not 100% sure.
>>>
>>>
>>>   curtis
>>> On 10/26/10 10:00 PM, Richard Jones wrote:
>>> Hello,
>>>
>>> As I pointed out during our Monday physics meeting, event sizes for pythia minimum-bias samples are right now around 50kb.  I have made the event record distributions, grouped by detector and type of information stored, and posted them on the web page below.  The FDC is the largest contributor, at around 75% of the total payload.
>>>
>>> http://zeus.phys.uconn.edu/halld/hdgeant/sizes-10-2010
>>>
>>> -Richard Jones
>>>
>>>
>>>
>>>
>>>
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>>>
>>>
>>> --
>>> Prof. Curtis A. Meyer           Department of Physics
>>> Phone:  (412) 268-2745          Carnegie Mellon University
>>> Fax:    (412) 681-0648          Pittsburgh PA 15213-3890
>>> cmeyer at ernest.phys.cmu.edu<mailto:cmeyer at ernest.phys.cmu.edu>    http://www.curtismeyer.com/
>>>
>>>
>>>
>>
>>
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