sPHENIX tracking discussion

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

Hi All,

Here are the minutes of today's tracking meeting. The talks are posted at:

https://indico.bnl.gov/conferenceDisplay.py?confId=2865

Best regards

Tony

Itaru Nakagawa - INTT material budget plan
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Itaru described the INTT ladder structure and discussed the material budget.

Slide 5: These numbers are different from the material scan with the ladder model in G4.
Itaru thinks the numbers in this slide are with overlaps. He will follow up with Gaku on the
discrepancy.

There are several possibilities for reducing the material thickness that are being pursued.
These include for the HDI card using copper mesh instead of plate for the ground shield. This
could reduce the copper thickness from 0.4% to 0.04%. Have to study the effect on noise
performance, however.

Slide 12: What is an acceptable temperature gradient? Answer: Don't know yet. Thermal expansion
of the HDI card being different at different temperatures can bend the card. Need a model, once
the temperature gradient is known. The acceptable temperature range for the PHENIX FVTX was
about 4 degrees C, so that is our criteria for now.

Slide 14: Christof Roland said that the Kalman filter has multiple scattering included. The problem
with electrons is due to Bremmstrhalung energy loss. See Christof's slides later in the meeting.


Christof Roland - sPHENIX tracking studies
---------------------------------------------------------
Christof has joined the sPHENIX tracking effort. He showed results of calculations done with
a toy tracking package:

www.hephy.at/project/ilc/lictoy/UserGuide_20.pdf

that sets up a simplified geometry and tracks particles using a Kalman filter. It includes
a proper treatment of multiple scattering through the Kalman filter, but does not simulate energy
loss (only matters at very low momentum). It is useful for initial evaluation of tracking designs.

It reproduces quite well the ALICE performance from full simulations.

For the plots shown here, the tracks are at 85 degrees in theta.

There was some discussion about how the TPC position resolution was determined. In the toy
calculation here it was assumed to be constant and set to 120 microns. It really depends on drift
length, but things are complicated by the trade off between pad size and diffusion.

Slide 9: Toy model indicates that there may be room for improvement in our full simulation.

Slide 12: For electron reconstruction the LHC standard is the "Gaussian Sum Filter", which
allows for kinks due to Bremsstrahlung.
Carlos: does ALICE do this? Christof will talk to them and see how they deal with this.
Carlos: The GSI group in ALICE works with electrons.

Can we use this toy package to investigate eta dependence? Yes, have not done that yet but it can be done.
slide 4 has Z = +/-80 cm. Christof: will make it +/- 1100 cm when doing eta dependence studies.

slide 18: The TPC was at 1/2 mm resolution for these calculations. Christof will update this.

Christof noted that ATLAS and CMS have 3-layer pixel track seeding. These are then extrapolated out to the
rest of the tracker.

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

---

From: Frawley, Anthony
Sent: Thursday, February 16, 2017 3:39 PM
To: sphenix-tracking-l AT lists.bnl.gov
Cc: Frawley, Anthony
Subject: Details for sPHENIX tracking meeting February 17, 2017

 

Hi All,

The agenda page for the tracking meeting on Friday morning at 9:00 am is:

https://indico.bnl.gov/conferenceDisplay.py?confId=2865

I am expecting a presentation from Itaru on the intermediate tracker.

Best regards

Tony