sPHENIX is a new detector at RHIC.

[John Haggerty <haggerty AT bnl.gov>]

Gunther and Dave,

On 10/24/17 11:56 AM, Gunther M Roland 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."

Here are some words which are certainly not be the final, but I know 
this is urgent so I thought I'd try and put some words out there to try 
and push this conversation along and perhaps we can communally come up 
with something better wordsmithed:

The changes largely preserve the unique sPHENIX capabilities for hard 
probe physics at RHIC, although the truncated acceptance of the EMCAL 
reduces the statistical reach by as much as 25% and the reduction in 
thickness of 1-2 interaction lengths and empty space within the 
calorimeter volume creates the risk of leakage of energy out of the 
detector which may have consequences which are not fully understood.  It 
will not be possible to restore the EMCAL acceptance once the sector 
construction begins.

> 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.

I would also avoid "catastrophic," I had a problem with that word in a 
previous incarnation, and I don't think what we're talking about is 
really catastrophic, but the closer we get to building something that's 
not that different from what is already done at RHIC, the less reason 
our handlers would have for paying for it.

> Best,
>
> Gunther and Dave
>
> > On Oct 24, 2017, at 11:22 AM, woody <woody AT bnl.gov 
> > <mailto: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 ansphenix-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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--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358