sPHENIX tracking discussion

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

Hi Darren,

Thanks, that is very helpful input! I think this makes it even clearer that it is imperative for us to have realistic simulations for the reused VTX pixels in sPHENIX. 

For a B-tagged jet measurement using track-counting and requiring 3 or more tracks, that efficiency would be a problem.

Rather than wait for a full model in G4 of the reused pixels, I would favor starting out with a cylinder cell geometry simulation containing random inefficiencies at this level, just to get a feel for the impact on the various physics topics sooner. But we will eventually need the full model in G4.

Thanks again,

Tony

---

From: Darren McGlinchey <Darren.McGlinchey AT Colorado.EDU>
Sent: Friday, January 29, 2016 4:37 PM
To: Frawley, Anthony
Cc: sphenix-tracking-l AT lists.bnl.gov
Subject: Re: [Sphenix-tracking-l] Minutes of sPHENIX tracking meeting January 29, 2016

 

Hi All,

I thought I'd chime in regarding the following comment in the minutes about the dead & active area in the current VTX pixels:

What is the dead space at the end of each sensor? Rachid will check. Comment: the dead area around the edge depends on the chip. 
Mike: There are two questions - we need both the intrinsic dead areas and the dead pixel map for simulations.
With the dead area that exists in the pixels already, it may not make sense to worry too much about gaps between sensors.

We've been working on this a lot lately to try and understand our track matching efficiency in Run 14 Au+Au and Run 15 p+p data. You can find some information about the pixel sensors on the VTX offline wiki (https://www.phenix.bnl.gov/WWW/offline/wikioff/index.php/General_Description). According to the information there for a given sensor in B0 or B1 (pixels):

Fraction of sensor active area in phi: 85.3% 

Fraction of sensor active area in z:   98.0%

Fraction of sensor active area phi x z: 83.6%

Therefore, if you assume no overlap between sensors in phi (not quite true), and require hits in both B0 and B1, the probability of having both hits with 100% live channels is already 69.9%. This is not a negligible number. To give some context, a reasonably good run (run 423844) in Run 15 p+p has 92.9% live channels in B0 and 77.2% live channels in B1. This gives an efficiency for having a hit in both B0&B1 of 71.7% from the fraction of live channels alone, which is comparable to the efficiency from the fraction of active area. Combining the two gives an efficiency for having a hit in both B0 & B1 of ~50%. These rough numbers seem to be matching up reasonable well with what we see in single particle simulations. This is also why most other tracking detectors have redundant layers, and don't require a match in 2/2 layers. I will reiterate that these numbers are rough, and should be updated with more exact values. The 98% active area in z does not account for the slightly larger gap between half-ladders at z=0, and the 85.3% active area in phi does not account for overlap between ladders in phi.

Also, I'm happy to provide realistic dead channel maps for the pixels to be used in simulation. Feel free to let me know what is helpful.

Thanks.

-Darren

----------------------------------------------------

Darren McGlinchey

University of Colorado, Boulder

darren.mcglinchey AT colorado.edu
----------------------------------------------------

On Fri, Jan 29, 2016 at 11:39 AM, Frawley, Anthony <afrawley AT fsu.edu> wrote:

The minutes of today's tracking meeting are below. The slides are posted at:

https://indico.bnl.gov/conferenceDisplay.py?confId=1719

Cheers

Tony

sphenix tracking meeting, January 29, 2016
---------------------------------------------------------

Itaru Nakagawa - strip tracker status:
-------------------------------------------------

Itaru reported on the status and future timeline of the strip tracker silicon R&D.

Ed: Can you send me a couple of slides outlining what you have done for R&D in last 6 months and what will happen in next 6 months. Useful to have this in hand if questions are asked.

Rachid: Can you send us the table of sensor characteristics so we can decide which ones are better? Helps to choose the testing order.

It will be early March for the next funding news - will learn then if we make the interview. Maybe April for the actual funding decision.

Rachid Nouicer - integration of the silicon pixels into sPHENIX:
----------------------------------------------------------------------------------

Slide 4: The outer tracking envelope is at 75 cm or 80 cm? Ed is still checking, will report later.

slide 6: How much do the sensors overlap in phi? We should start by using the same overlap as in the VTX, see slide 5 for the configuration.
Rachid will check that slide 7 has the same sensor overlap as the VTX. Mike: You may have to fiddle with radius to get the 12 sensors to fit nicely, but will need to check if the result satisfies all engineering stay clear boundaries.

What is the dead space at the end of each sensor? Rachid will check. Comment: the dead area around the edge depends on the chip.
Mike: There are two questions - we need both the intrinsic dead areas and the dead pixel map for simulations.
With the dead area that exists in the pixels already, it may not make sense to worry too much about gaps between sensors.

We need to know how the number of active pixels that overlap at each gap in sPHENIX affects the momentum measurement at low momentum. Mike said we could use the VTX simulations and scale the bend by the magnetic field ratio. Remember that at some point we are ruled by multiple scattering.

Action item: Rachid will get back to us by email with an overlap geometry for the pixels, we will then do some crude estimates  of where the momentum measurement is affected. Note that every other ladder is staggered in radius.
 
Mike: At some point we need the GEANT 3 geometry ported to GEANT 4, so we can simulate the actual proposed configuration.

Tom Hemmick - Brief TPC update:
----------------------------------------------

Slide 3: Ed: do you need help from BNL? Tom: yes, need professional engineering to discuss details of how to do the machinable foam. Ed: bring Niv to BNL, set up a meeting with BNL engineers and experts.

Tom: still trying to figure out which foam to buy. Four densities on the market, more expensive with density. Not sure if the lightest density foam will work. Ed: Mike Lenz has experience with foam.

Mike McCumber - MAPS layers for sPHENIX:
-----------------------------------------------------------
Mike made a verbal report, but uploaded a few slides after the meeting. He reported on three areas that are being pursued.

Slide 3: LANL LDRD funding: Mike outlined the path and timeline.

Slide 4: Exploring collaborations. Working hard on establishing ties with LBL now.

Slide 5: Santa Fe MAPS cost and schedule workshop. Three day workfest to produce cost and schedule document for the inner tracker, and a full tracker option.

Discussion:
Ming is working on when the needed experts are available. Will define the workfest schedule around the schedule of experts (Luciano Musa, Leo Greiner, ... ).
Dave: An earlier date would be better. Does the request for CD0 in April mean this should be before April? Ed: the CD0 does not address the scope, so they are in principle not coupled. Comment: won't DOE want to have an idea of the scope before awarding CD0?

Ed: What would the full tracker outer radius be? The outer radius with 1.5 T field would be 60 cm. With 1.4 Tesla it would increase to about 64 cm.
We were told by Luciano in his presentation that a CERN engineer thought the ALICE ladders would work without re-engineering at the increased radius. That opinion would need to be checked carefully.

Mike would like to get from Berkely the MAPS geometry in simulation, and hopes to do that when he visits LBL in two weeks.

Discussion of the review recommendation that we should focus on reusing the pixels. Ed commented that we do not have to follow the review, if we make a good case for not doing so.  In this case the response will be a document that outlines the MAPS plan and justification. The response would be needed by the time of the next review (probably next Fall?). We need to think about the time scale for preparing the document. The intended audience is Berndt Mueller and David Lissauer. 

Ed noted that there is a web page for review comments and responses.

Dave: When do you think you can settle on a date for the workfest? Mike said they will push hard to get it defined in the next week.

---

From: Frawley, Anthony
Sent: Thursday, January 28, 2016 10:44 AM
To: sphenix-tracking-l AT lists.bnl.gov
Cc: Frawley, Anthony
Subject: sPHENIX tracking meeting Friday January 29 at 9:00 am ET

 

Hi All,

We will have an sPHENIX tracking meeting tomorrow, Friday January 29, at 9:00 am ET. The agenda page is:

https://indico.bnl.gov/conferenceDisplay.py?confId=1719

At present we are expecting to hear from:

Rachid Nouicer - Update on reused pixels integration

Tom Hemmick - TPC progress

If anyone else would like to add an agenda item, please let me know.

Tony

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