sPHENIX is a new detector at RHIC.

["Frawley, Anthony" <afrawley AT fsu.edu>]

Hello Ed and All,

I think it is time for us to make clear to Berndt that our original scenario of reusing the PHENIX pixels in sPHENIX has become increasingly unattractive as we learn about it and evaluate it with more realism. This process has now reached the point where those who are familiar with the likely performance do not consider this to be a real option - it would kill most of the physics program.

That is where we are, and where we have to start from.  We can not start from a baseline design that we now believe will not deliver most of the physics program.

I think it is very reasonable for us to start by considering a tracker that we know will a) work and b) deliver the physics, and measure the performance of all of our proposed tracking solutions relative to that. A 7 layer MAPS tracker serves that function well. This does not mean that we think we can afford to buy one within our $75M limit.

There is now no question in my mind that any realistic tracking solution we adopt will cost more than what we presented in the cost and schedule review. The cheapest solution is a TPC and an inner barrel for displaced vertex measurements. The only thing that makes sense for the inner barrel at this stage is a MAPS tracker following the design of the ALICE ITS upgrade. In that cheapest tracking scenario, we replace a "free" inner barrel with one costing $3-4M (maybe less, if we consider only 2 layers).

But it also should be clear to everyone that the TPC solution has not yet reached the point where we can say it will work, or that it will work without being backed up by intermediate tracking layers such as are used in STAR and ALICE. Having to add supporting tracking layers would mean that the effective TPC cost is underestimated and will need to be increased. One of our goals in the next month is to try to have a first look at that.

Therefore it would be remiss of us to not look at the cheapest alternatives we can come up with, and evaluate them. When we discuss outer MAPS layers or other silicon options that is really what is being suggested. 

Finally, a comment on your comment:

" Here is my proposal:
    1) Agree that whatever Tracker solution we adopt will be
    cost neutral, i.e $5M AY in material cost + 40% contingency.  That is what we should
    tell Berndt. Whatever solution we choose will be cost neutral."

I think that this is the last thing we should tell Berndt. What I have said above is that I do not believe that it is possible for us to build a tracker that will deliver a large part of the physics program for $5M AY material cost and 40% contingency, since that is our estimate for a TPC alone. If there is disagreement about that we should hash it out, but we need to do that before we promise that we can deliver our physics program for a price that is just not possible.

Best regards

Tony

---

From: sphenix-l-bounces AT lists.bnl.gov <sphenix-l-bounces AT lists.bnl.gov> on behalf of Lajoie, John G [PHYSA] <lajoie AT iastate.edu>
Sent: Wednesday, April 27, 2016 2:40 PM
To: EdwardOBrien; sphenix-l AT lists.bnl.gov
Subject: Re: [Sphenix-l] [Response to ADL charge] Continuing detector scenario discussion

 

Hi Ed,

    Is it possible to separate these two issues (what we simulate and what we build)?

    As you say, for the cost exercise we will just have to adopt a budget that it will have to fit into - as you suggest $5M AY + 40%.  That's fine.

    However, for the simulations we have to choose something. I would think that a MAPS tracker would be more straightforward to implement in the simulations, and is less difficult to justify (in terms of the "reality" of the simulations) than an "ideal" TPC.  (I am more than happy to be shown to be incorrect.) The statement then becomes for the reference design that we ultimately want performance *similar to what was used in the simulations*. It doesn't say that it is the exact implementation that is in the simulations.

    You can argue that this implementation is unrealistic for budgetary reasons, but I don't think either option passes the laugh (or smell) test at this point.  So let's decouple the simulations from the tracking choice and give both options time to evolve.

  In this way I don't think we violate dramatically what we have told BNL, and we can decouple the choice of the tracker from the need to get simulations going now.

John

On 4/27/2016 1:09 PM, EdwardOBrien wrote:

    Dear Gunther,
      I have a very strong opinion on the issue of the baseline detector.
    The Project team has been telling Berndt for months
    that the sPHENIX baseline design is a the EMCal and HCal as
    specified in the pCDR plus the reused pixels and compact TPC.

     Why? Because the project has been given a very strict guideline on
    total cost. The TPC cost including manpower that we'd have to pay for
    has been looked at carefully and we believe that this is the cheapest option
    by far unless there is outside money, such as JSPS money, to build
    something else.

    If the collaboration wants to propose that the baseline is changed to 5-6
    layers of MAPS as the Tracker then you better bring that to Berndt
    before you do anything. Unfortunately, it won't pass the laugh test.
    On cost alone the 7 layer ALICE ITS is estimated at $30M with a low contingency
    and standard US accounting.

    In addition the November Cost and Schedule review committee concluded that
     cost aside, the collaboration had neither the schedule nor expertise to
    pull off a MAPS pixel detector. Despite the hard work of one person
    at LANL there has been little progress on the MAPS option since November
    beyond his effort. I'd also like to point out that nothing beyond
    the inner 3 layers of the ITS was discussed in the plenary session of the
    Santa Fe workshop. Now some are proposing 5 layers minimum.

    Here is my proposal:
    1) Agree that whatever Tracker solution we adopt will be
    cost neutral, i.e $5M AY in material cost + 40% contingency.  That is what we should
    tell Berndt. Whatever solution we choose will be cost neutral.

    2) Independently complete that Cost and Schedule exercise on MAPS that was started
    at the Santa Fe workshop. Mike McCumber has started on it. We have a standard approach to
     this that has been applied to all the subsystems, except the si strip Tracker option,
     and it needs to be applied to MAPS.

    3) Recommend a cost reduction of $4-4.5M plus contingency and simulate that
     before the May deadline.

    These 3 suggestions imply that no reduction will be taken from the $5M
    set aside for the Tracker.

    I suggest that you and I run this by Berndt before we go to a lot of effort and find
     that he wants something else. Thanks.

    Ed

On 4/27/2016 11:31 AM, Gunther M Roland wrote:

On Apr 27, 2016, at 9:06 AM, Lajoie, John G [PHYSA] <lajoie AT iastate.edu> wrote:

(2) Project/Collaboration management just make a (damn) decision. The choice of a tracker for a reference design at this point does not need to imply or bias a final decision and neither side should take it as such. It is a necessary expedient at this time. 

Now let me go out on a limb and anger part of the collaboration. Given (2) I would choose to simulate a MAPS (full ALICE ITS) tracker option at this time as opposed to an "ideal TPC". As we will be investing a lot of effort in these simulations I think they would have a longer useful lifetime for future reviews, etc., if we use a more realistic simulation.  If we use an "ideal TPC" I think that opens us up to potential criticism we don't need.  Just my $0.02.

We can argue about this ad infinitum. Neither option is fully developed and we will revisit this situation again. I've expressed a preference, but my main point is that the pain of making a decision is outweighed by the danger of dragging this on too long.

Hi John,

Thanks for your comments, and thanks for being frank! We should make the decision very soon (24h?). I hope more people will weigh in shortly. We are talking to the simulations gurus to make sure that we don't decide on a reference configuration that we are not actually ready to simulate right away. 

Gunther

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John Lajoie

Professor of Physics

Iowa State University

 

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