sPHENIX tracking discussion

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

Dear Jin and All,

Yes, Mike McCumber pointed out to me in a private email before I went to dinner tonight that we really wanted the lengths to be larger. Measuring eta = +/- 1.1 relative to Z=0 is not so bad for the TPC and calorimeters because of their large radius, but for the inner tracking layers it produces a significantly reduced acceptance when we have a Z-vertex distrib ution covering +/- 10 cm.

I assumed that the inner tracker layers should cover the acceptance of the back end of the TPC viewed from Z = +/- 10 cm , and calculated the following lengths for the MAPS and INTT layers:

Layer radius (cm)         layer length (cm)           

   2.3                                      25.6
   3.2                                      27.8
   3.9                                      29.6   // The 3rd layer of the inner barrel is 27 cm, so not quite this long
   6                                         34.7
   8                                         39.6

  10                                        44.5

  12                                        49.4

  78                                        211   // sanity check - back end of TPC

While I was at dinner, Jin Huang also commented on this, and Walt Sondheim sent a drawing illustrating it to a private list. He got numbers for the INTT lengths that are very similar to mine. Walt, could you send your nice drawing to the tracking list?

This significantly increases the number of sensors in the INTT layers. I think we need to have a discussion about whether we agree that this is what we need.

Cheers

Tony

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From: Huang, Jin <jhuang AT bnl.gov>
Sent: Wednesday, September 7, 2016 8:22 PM
To: Frawley, Anthony; sphenix-tracking-l AT lists.bnl.gov
Subject: RE: INTT layer length

 

Hi, Tony

 

As I understand these length are covering to pseudo-rapidity of 1.1 from z = 0 cm. However, I would prefer it covers for larger z range, which at least match the length of MAPS (+/-14cm). In that scenario, a minimal length could be set by given radius intersecting a straight line connecting the outer corner of TPC active volume (R, z = 78, 104 cm) and the far corner of MAPS layer 3 (R, z ~ 3.9, 13.5 cm).

 

Cheers

 

Jin

 

______________________________

 

Jin HUANG

 

Brookhaven National Laboratory

Physics Department, Bldg 510 C

Upton, NY 11973-5000

 

Office: 631-344-5898

Cell:   757-604-9946

______________________________

 

From: sphenix-tracking-l-bounces AT lists.bnl.gov [mailto:sphenix-tracking-l-bounces AT lists.bnl.gov] On Behalf Of Frawley, Anthony
Sent: Wednesday, September 7, 2016 5:32 PM
To: sphenix-tracking-l AT lists.bnl.gov
Subject: [Sphenix-tracking-l] INTT layer length

 

Hi All,

 

I made some estimates of the required length of the silicon strip layers in the intermediate tracker. The lengths required to match our acceptance of eta within +/- 1.1 units are:

 

Radius (cm)          length (cm)       minimum sensors/half-ladder

6.0                              +/- 8.1                    7 x 2 = 14

8.0                            +/- 10.7                    9 x 2 = 18

10.0                          +/- 13.4                    12 x 2 = 24

12.0                          +/- 16.1                    14 x 2 = 28

 

where the minimum sensors /half-ladder number assumes 1.2 cm long sensors, and is rounded up to completely cover the acceptance.

 

Cheers

Tony