sPHENIX MAPS tracker discussion

[Anthony Frawley <afrawley AT fsu.edu>]

Hello Sookhyun and All,

It is clear that we need 3 layers of MVTX if we are going to project tracks to the INTT or TPC, giventhe low  average transverse momentum we are expecting.

Addition of some modest dead areas in the MVTX will not affect most of the tracks from a collision. Therefore I would be surprised if they had much effect on vertex finding using triplets. It is easy to test though.

Regarding possible (occasional) 2-hit tracklets - one could include the event vertex position in the track fits as long as there were at least 2 triplet tracks. In principle, adding the event vertex to the track fit would allow an estimate of the track momentum with only 2 MVTX hits. The vertex itself would be found using all tracklets from that collision, so would most likely provide a precision comparable to the MVTX layers. This would lead to a somewhat circular logic for 2-hit tracks of course, but it would allow projection of those MVTX hits to the INTT layers, providing a test of whether those MVTX hits are in time or not. This could matter in a high rate pp environment.

Cheers

Tony

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From: sPHENIX-MAPS-l <sphenix-maps-l-bounces AT lists.bnl.gov> on behalf of Xin Dong <xdong AT lbl.gov>
Sent: Tuesday, October 9, 2018 4:21 PM
To: dr.sookhyun.lee AT gmail.com
Cc: sphenix-intt-l AT lists.bnl.gov; sphenix-maps
Subject: Re: [Sphenix-maps-l] In-time vertexing with INTT

 

Hi Sookhyun,

Thank you for this nice study. Let me back off a bit and ask a couple of basic questions first.

Can you elaborate the definition of "in-time vertex identification efficiency"? My understanding from the slides is the probability of reconstructed vertices with 3 MVTX+1 INTT to be the truth MC vertices. I may be wrong here, and would appreciate your clarification.

What is the minimum number of tracks requirement in the vertex algorithm?

Do you also have the vertex finding efficiency? Fraction of MC truth vertex that got reconstructed. May be also interesting to see this vs. event multiplicity at different luminosity levels.

I tend to agree with Ming that 3 MVTX hit seems to be a bit tight. What if there are some small amount of dead areas on each layer of MVTX during the real operation. The dead area fractions in three layers will add up if we have the 3-hit requirement. This may cause some sizable vertex finding efficiency loss, isn't it?

Thank you and Best Regards

/xin

On Tue, Oct 9, 2018 at 11:00 AM sookhyun lee <dr.sookhyun.lee AT gmail.com> wrote:

Hi Ming,

Yes, so far I only used 1 INTT layer to discriminate against out-of-time events. We certainly should reconstruct tracks using 2 MVTX hit + (2+) INTT hits at next iteration, but 2 MVTX hits only won't provide good starting curvature (for phi segmentation) or z0 parameter (for z segmentation) for INTT, thus cannot be used for in-time vertexing. I did not apply any pT cut on tracks used for vertexing.

Best regards,

Sookhyun  

On Tue, Oct 9, 2018 at 12:14 PM Ming Liu <ming AT bnl.gov> wrote:

Hi Sookhyun,

Nice work! So in your analysis, only one INTT hit was used to tag in-time association to a MVTX triplets? How about if you only use MVTX tracklet with two hits only? Have you applied any minimum momentum cuts?

Cheers 

Ming

Sent from my iPhone

On Oct 9, 2018, at 9:52 AM, sookhyun lee <dr.sookhyun.lee AT gmail.com> wrote:

Hello everyone, 

Please find my updates on in-time vertexing with INTT below.

https://indico.bnl.gov/event/4036/contributions/24340/attachments/20294/27121/intt_in-time_vertexing_Oct8_2018.pdf

 

Let us have discussions tomorrow at Inner tracking task force meeting as well.

Best regards,

Sookhyun

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===========================
Xin Dong
Staff Scientist, Nuclear Science Division
Lawrence Berkeley National Lab
MS70R0319, One Cyclotron Road
Berkeley, CA 94720, USA
Tel: +1-510-486-4121
Email: XDong AT lbl.gov
===========================