sPHENIX is a new detector at RHIC.

["Lajoie, John G [PHYSA]" <lajoie AT iastate.edu>]

Hi Gunther,

    This was discussed a bit in the simulations meeting yesterday, and I completely agree with this approach. If we could get the simulations machinery churning very soon on a reference configuration it will allow us to work out some of the kinks and give us clear baseline for comparison.

    As you describe it, the reference configuration is well-defined with the exception of the tracking.  This split pathway has generated a great deal of discussion since last fall, and rightly so. However, at this point it is just getting in our way. At the present time we are not ready to make a final tracking choice, but we *need* to do one of two things:

(1) Simulate reference designs with *both* TPC and MAPS tracker options. I think this is unrealistic as it doubles the required manpower and resources (CPU and disk space) and diverts effort from the primary goal of answering the ALD charge.  I personally discard this option.

(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.

John

On 4/26/2016 9:34 PM, Gunther M Roland wrote:

Friends,

We had a very useful discussion yesterday. We are pulling together a summary and additional information that will be distributed shortly. We urgently need to make several initial decisions to allow the simulation and software teams and the topical groups to start studying options. On the other hand, we need to be reasonably sure that we don't invest time into defining and evaluating options that might turn out to be irrelevant. 

A possible "safe" start would be to begin by evaluating capabilities/performance/physics plots for a "reference configuration". That will (a) provide a reference to quantify the loss of physics performance for various "best worst case (BeWoC)" (tm JN) choices, (b) provide an existence proof for a ~realistic detector that can achieve our physics goals and (c) allow everyone to get going with their studies while we hash out the (few!) BeWoC  scenarios.

Following the discussion yesterday, our suggestion for the "reference configuration" would be to use the "$82M" design for the EMCal, inner HCAL and outer HCAL (and magnet...) and complement this with a tracker consisting of either (a) 3-layer ALICE ITS MAPS IB copy + ideal TPC or (b) full ALICE ITS copy (IB + middle and outer layers). Here "ideal TPC" refers to assuming (near-) perfect correction of space charge distortions.

Please consider these suggestions and if you believe you have a better suggestion of how to get the actual simulation/physics study effort going, or have a better suggestion for a reference configuration, continue this thread. Let us repeat that the process to define the final BeWoC's has to go ahead in parallel over the next days. Stay tuned. 

Cheers,

Gunther and Dave

 

--

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie