sPHENIX EMCal discussion

[John Haggerty <haggerty AT bnl.gov>]

Dennis,

We put in the CDR, without any great justification, that we'd have 25% 
occupancy in the EMCAL and that results in 150 kbyte/event.  That 
assumed 12 samples (24 bytes) per hit... a little low compared to more 
recent assumptions of 16 samples/hit.  We have not defined the zero 
suppression algorithm, either, but I would imagine something that looks 
for the first (or first few) samples x counts above pedestal and then 
records a few "pre" samples followed by samples that capture the pulse.

If we were to skip zero suppression and just record 16 samples in every 
channel of the EMCAL, that would be around 800 kbyte/event, so at 15 kHz 
that would be about 95 Gbit/s

You can check my arithmetic or try your own variations, there are 96*256 
channels in the EMCAL, 14 bit samples are stored in 16 bit words and the 
other numbers are above.

Impossible to record it all?  Well, we have been moving the boundaries 
of the possible in this area.

On 12/19/18 1:55 PM, Perepelitsa, Dennis wrote:
> Hi EMCal group,
>
> There was some discussion at the recent Collaboration Meeting regarding 
> whether we would read out every EMCal channel every event, or if there 
> will be some zero / noise suppression. For the heavy ion jet 
> reconstruction, it may be important to have every channel to get both 
> positive and negative noise fluctuations.
>
> What is the current thinking or plan for both p+p and Au+Au running? 
> What do the currently estimated data throughput and volume numbers 
> assume in terms of information from the EMCal?
>
> Dennis
>
> Dennis V. Perepelitsa
> Assistant Professor, Physics Department
> University of Colorado Boulder
>
>
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--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358