sPHENIX tracking discussion

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

Hi All,

Here are the minutes of the tracking meeting last week. Sorry for the delay.

Best regards

Tony

Tom Hemmick: TPC hardware update
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Tom reviewed the progress on the TPC mechanical design.

Slide 3: The outer radius of the TPC is fixed at 78 cm by Don Lynch.

Slide 4: Dave: Is the endcap different from that in STAR?
Tom: STAR is a wirechamber, and has an exceptional flatness spec for the pad plane. We have less of a flatness requirement due to GEM use.
We use smaller segmented modules (~20 cm in radial direction, and 1/12 of the azimuth). This arrangement has a gap between modules, but it improves reliability and stability, and makes replacement easy. The GEMS can be double sided or single sided etched, due to their smaller size.
A high precision mesh in front of the GEM stack in each module makes for a precise electric field. Philosopically, the mesh is part of the field cage, but is attached to the GEM module. The mesh is effectively electrically continuous, tied to the field cage.

Slide 13: Dave: You have to name "ne2k" after sPHENIX!

Tom: Outlook:
The hardware is pretty advanced.
For the simulations we need stacking of events. We need the ionization statistics investigated a bit more for the simulations, would like to look at this a bit more.  
For the electronics - things are less well developed. Takao said there would be a meeting next week to discuss the electronics. There will be a C&S mini-review before the tracking review.
For computing on the back end, we need to understand the data flow better.

Dave brought up the idea of a non-zero crossing angle of the beams to reduce the rate of useless collisions outside the 10 cm diamond. There have been discussions with Wolfram about this. Tom said that sounds very good, please explore it! If we can reduce the collision rate from 50-100 kHz to 15 kHz or so, it would be a big help. Are there measurement implications to the crossing angle?

Carlos Perez Lara: TPC software status:
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Carlos briefly reviewd the status and objectives of the TPC software effort.

Tom stressed that Alan Dion is leaving sPHENIX and it is vital that we have a group of people who can develop and maintain the tracking code. The group presently working on it is:  Carlos, Veronica, Prahkar, Sourav, Sook Hyun, Klaus, TKH, Mike.


Mike McCumber: MAPS progress
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Mike made a verbal report on the MAPS detector status.

He is working on lining up external collaborators, pre the tracking review. Ed: Let me know how PM can help with this. We want to be able to say at the tracking review that these groups are committed.
Mike is also looking for agreement on shared resources from Luciano Musa.
Ed commented that the draft mini-review report is close to ready to release.

There was a brief discussion about the realistic MAPS ladder code priority. The conclusion was (again) that the tools need to be finished first with the cylinder cell code, then we come back to the ladder implementation. We would like to have the current MAPS + TPC code working very well before the tracking review, and before we add a big change in the geometry.
Jin: It would build confidence in the results to have confirmation that the ladders do not change any conclusions, but agree that this is not critical for the review.
We would like to be able to say at the review that we are working on it and making good progress.

There was a brief discussion about a possible intermediate tracker between the TPC and inner MAPS detector.
Ed: It is important to understand if it is a net positive or negative. Would we agree to build it if we had external funding?
Mike: It will boil down to: how many space points in the inner barrel do we need to confirm a TPC track? Is it greater than 3? If so, we need an intermediate tracker. Once the event pileup code is working we will be able to explore this.

Mike said to schedule him for a progress report on event pileup at the next meeting.