sPHENIX is a new detector at RHIC.

[Rosi Reed <rjr215 AT lehigh.edu>]

Hi Gunther and everyone,

I don't think I'd personally label the changes as "catastrophic"...
It is difficult for me to understand all of the different political
aspects, but one thing I worry about is what this means for the "next"
descoping exercise.  There is a point where I really think we need to
say "this doesn't make sense".  I don't think we are there yet, but my
understanding is part of the issue that we are facing is due to the
increase in the price of steel.  What if this continues to increase?
Will we need to descope the HCal further?

Perhaps as a collaboration for later (obviously too late at this
point), we perhaps should discuss where this line might be in terms of
performance.

Secondly, it's not clear to me to what degree all these time scales
matter.  For instance, if we have a later CD-1 but get to keep the
entire HCAL and EMCAL, that might be beneficial.  I really don't know,
however.

I guess what I'm thinking is there a way to diplomatically phrase this
sentence in way that implies we are approaching catastrophe, even if
we are not there yet?  I can't think of one without adding an
additional sentence (perhaps as American I prefer short sentences....)

Cheers,

Rosi

On Tue, Oct 24, 2017 at 11:56 AM, Gunther M Roland <rolandg AT mit.edu> wrote:
> Dear Craig, Rosi, John et al,
>
> Many thanks for the valuable comments! As time is somewhat limited, it might
> be most efficient if we could discuss a few concrete suggestion for
> replacing the key statements about the impact of the proposed descoping
> solution on the expected physics performance. It is probably most useful to
> focus on the sentence that is repeated in executive overview and summary
> (with a typo already fixed):
> "The changes, which result in significant but manageable reduction in
> expected statistical reach and jet reconstruction performance, preserve the
> unique sPHENIX capabilities for hard-probe physics at RHIC."
>
> One we have found an improved expression of the collaboration's sentiment,
> we'll update the other relevant paragraphs in the document accordingly.
>
> We should probably be mindful that the exact choice of phrasing may have
> real consequences with respect to Berndt's planned visit to DOE - i.e., if
> the changes are considered "catastrophic" one would presume that we will
> only go ahead once funding for the full scope is identified or if we say
> that "The changes,...., threaten the unique sPHENIX capabilities..." one
> might want to reconsider going for CD-1 in early 2018. We need to make sure
> this describes the impact accurately and supports the path forward the
> collaboration is pursuing.
>
> Best,
>
> Gunther and Dave
>
> On Oct 24, 2017, at 11:22 AM, woody <woody AT bnl.gov> wrote:
>
> Hi All,
>   I just want to support what Rosi and John have said. I don't think we want
> to imply in the Descoping Document that "we're fine" with the proposed cuts
> in either the EMCAL or the HCAL, and I would not use words like "these
> losses are not catastrophic", since I believe that is exactly how this would
> be interpreted. For the EMCAL, I looked more carefully at how we would save
> the $1.1M before contingency from the EMCAL alone (not counting the
> electronics), and, because of the fixed costs involved in building the
> sectors, the cost savings does not scale exactly with reducing the
> acceptance, although it does to a fairly good approximation (|eta| < 0.82
> rather than |eta| < 0.85). However, we should remember that the acceptance
> for the baseline design is |eta| < 1.1 so that we can have a fiducial regon
> of |eta| < 1.0 for physics, and we would still need to impose a similar
> fudicial cut on the reduced acceptance detector. This would imply our
> physics acceptance would be more like |eta| < 0.72, which would imply a loss
> of statistics of ~ 50% for the upsilon. Also, the boundary between the
> reduced acceptance EMCAL and the full acceptance HCAL (which may only be the
> outer HCAL) will certainly cause significant non-uniformities in jet
> reconstruction that we will presumably only really find out about after
> we've started actually analyzing the data. All of this certainly goes
> against the original design motivation for sPHENIX for having a larger
> acceptance jet spectrometer with uniform coverage, and I personally don't
> this this should be stated as "not catastrophic".
>
> Craig
>
> On 10/24/2017 8:35 AM, Rosi Reed wrote:
>
> Hello Everyone,
>
> First, attached are two plots for single jet and dijet containment.
> For the single jet containment, this is the number of jets a given jet
> pT within the EMCal acceptance over all jets of that pT.  For the
> dijet containment plot, this is versus the leading jet transverse
> momentum so they are on the same scale.  This is the ratio of the
> number of leading jets of a given pT where both the leading and
> subleading jet are within the EMCal acceptance (and the subleading jet
> has pt > 5) over the total number of leading jets with that momentum.
> The sub-leading and lead jets are |delta phi| > 2.35, there is no
> requirement that the sub leading jet be the highest pt sub-leading
> jet.
>
> I think this shows the statistical hit that we take with the reduced
> emcal, as we are unlikely to analyze Calo jets that are not fully
> contained within both the HCal and the EMcal.  The reason we would
> want to do this is illustrated in Figure 1.5.
>
> I can adjust these plots as needed up until about 4 pm today.
>
> Line 91: I highly doubt we can improve upon the nominal configuration
> using the reduced configuration with corrections ... the JES and JER
> are both affected for the worse, and this means the correction and
> unfolding will be more difficult.  In lines with what John has stated,
> I don't think we want to make it too optimistic.
>
> Regards,
>
> Rosi
>
>
>
> On Tue, Oct 24, 2017 at 12:26 AM, John Haggerty <haggerty AT bnl.gov> wrote:
>
> 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
>
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-- 
Rosi Reed
Assistant Professor, Physics Department
Lehigh University
(610)758-3907
16 Memorial Drive East Office 406
Bethlehem, PA 18015