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Hi Gunter, Dave and All,
I also like John's wording for the Executive Summary, but the
statement about reducing the statistical reach by 25% applies only
to straight jet physics, but for the upsilon, it will be more like
50%, and I think we should say that so that the impact of the
reduced acceptance on both physics programs is made clear. Also,
for the discussion about the upsilon later on in the document, I
didn't mean to imply in my previous message that if we didn't want
to say that "the losses were not catastrophic" that we would have
to say that they were catastrophic. I just think that
using words like catastrophic anywhere in the document is not a
good idea and we don't want people thinking in those terms, and I
guess other people feel the same way. I also fully appreciate the
danger of giving the impression that we cannot have a viable
physics program if we are forced to implement the descoping
scenario were are presenting, or that we can live with (albeit
painfully) with the proposed scenario, and that we are walking a
fine and delicate line between the two. However, l'll leave the
final wordsmithing of how to say that to those who are more
politically savvy than I am.
Cheers,
Craig
On 10/24/2017 1:50 PM, John Haggerty wrote:
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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cell: 631 741 3358
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