sPHENIX is a new detector at RHIC.

[John Haggerty <haggerty AT bnl.gov>]

Gunther and Dave,

Speaking as a high official of the project, it is good to see that the 
collaboration can agree on a plan to bring the costs within the 
boundaries the lab has asked.  As you know, I have looked into more 
radical changes without expending engineering effort on them, but I 
cannot see any better alternative to this proposal that could come 
anywhere near being ready in 202{1,2,3}

Speaking as a member of the collaboration, I think we should try to 
convey more of a sense of loss and sacrifice.  Cutting the emcal 
acceptance in particular seems like a double whammy, because it not only 
cuts the acceptance, it makes the whole calorimeter system thinner, and 
I have even wondered whether the un-descoped detector is thick enough, 
and with the Inner HCAL probably gone, the fiducial region is pretty 
small.  Experiments often recover that region with endcap or end plug 
calorimeters, but I don't think that's a viable option for us, because 
it introduces a boundary which is inherently non-uniform.

Another concern is the unknown unknowns we have introduced with the odd 
longitudinal segmentation in the calorimeters...  sure, there is now a 
lot of evidence that the signals look not so bad with this arrangement, 
but violating the conventional wisdom is often punished harshly by 
nature.  I don't know that we can say with certainty that the vast 
background ocean of low pt particles, jets, and slow secondaries which 
are now spinning around inside the magnet but outside the emcal do not 
have some very unfortunate effects.  I have not been able to put my 
finger on exactly what we should look for, but I think we have to keep 
looking for trouble.

I know these are not very well formulated objections, and so may be 
impossible to take account, but I thought it might be useful to put them 
out there in case it inspires someone smarter than me to see more 
clearly where we might be going off the rails.

On 10/21/17 12:02 AM, Gunther M Roland wrote:
> Friends,
>
> As discussed at the General Meeting today, we are forwarding draft 1 of our 
> document outlining the detector scope for a $32M cost cap. The pdf file can 
> be found at
> https://www.dropbox.com/s/5wyutbndogozm5q/sPH-GEN-2017-002_v1.pdf?dl=0
> (we'll provide another link tomorrow for those that can't access dropbox)
>
> Please send your comments in reply to this mail, keeping the 
> [sPH-GEN-2017-002] tag in the subject line***. Comments received by 
> close-of-business on Monday, 10/23, will be most useful.
>
> Cheers,
>
> Gunther and Dave
>
> ***we will move future reviews to an sphenix-notes-l AT bnl.gov list, but the 
> list couldn't be generated in time for this note.
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--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358