sPHENIX tracking discussion

[Christof Roland <christof.roland AT cern.ch>]

Hi Tony,

I investigateur a bit further. In the z dimension as you showed things look ok. 

In phi however the residuals and the assigned errors dont look ok, i.e. way to small. 

See attached slides.

But they seem to be tuned to eachother the pulls look ok.

Could someone familiar with the machinery check if we could make the axis lables of the QA plots readable?

Maybe we can discuss this in the tracking meeting. 

cheers

   Christof 

Attachment: MVTX_Residual.pptx
Description: application/vnd.openxmlformats-officedocument.presentationml.presentation

On 17. Jun 2022, at 18:12, Anthony Frawley via sPHENIX-tracking-l <sphenix-tracking-l AT lists.bnl.gov> wrote:

Hi All,

I attach plots of (cluster z - truth z) and (cluster z error) for the MVTX layers. These are made from some pp with pileup files that I made a few days ago. The sigma is about 6 microns, as expected, in the first plot, and the mean value of the error is 6 microns in the second plot. 

There is evidently a problem with the residual calculation. But I am puzzled by the observation from Christof that the error assigned by the MVTX clusterizer is 2.6 microns. That is not what I see in the cluster error histogram.

Tony

---

From: sPHENIX-tracking-l <sphenix-tracking-l-bounces AT lists.bnl.gov> on behalf of Hugo Pereira Da Costa via sPHENIX-tracking-l <sphenix-tracking-l AT lists.bnl.gov>
Sent: Friday, June 17, 2022 11:16 AM
To: sphenix-tracking-l AT lists.bnl.gov <sphenix-tracking-l AT lists.bnl.gov>
Subject: Re: [Sphenix-tracking-l] Wierd MVTX residual distributions

 

Hi Christof,

These numbers do look small indeed (at most 2um)

Last time I looked (a long time ago, in 2020), the residuals where more 
around 5um (all sizes included) (see plot attached)

I tried to look at the QA plots (e.g. 
https://urldefense.com/v3/__https://nbviewer.org/github/sPHENIX-Collaboration/QA-gallery/blob/jenkins-sPHENIX-test-tracking-low-occupancy-qa-2207-test-tracking_Event1000_Sum16/QA-Mvtx.ipynb__;!!P4SdNyxKAPE!F75K0bmn-hbMcsFeIvPKt82oxMU5ewYVpTmBqVfZs15PYCyUne7TebreJ2QYw1MQV_iJHQtTALmoj4PlgbsfVLxzMFu42Cm_nWUnQx9Yhg$) 
but we can't read the x axis there ... Not very useful, something that 
we should fix ...

Hugo


On 6/17/22 01:40, Christof Roland via sPHENIX-tracking-l wrote:
> Hi Everybody,
>
> i am in the process of producing the new error parameterizations so we can swith to TrkrClusterv4.
>
> Looking at the MVTX residuals I see distibutions that are way to narrow, as far as I understand.
> Here is a list of the observed RMS of the residual (cluster phi position - track phi position) distribution.
> There is the residual with respect to the truth track and the reco track as well as the a selection for cluster width in phi ==1 or bigger than one.
>   
> truth layer 0 phisize = 1 RMS: 0.000122
> truth layer 0 phisize > 1 RMS: 0.000164
> truth layer 1 phisize = 1 RMS: 0.000090
> truth layer 1 phisize > 1 RMS: 0.000126
> truth layer 2 phisize = 1 RMS: 0.000072
> truth layer 2 phisize > 1 RMS: 0.000102
> trk layer 0 phisize = 1 RMS: 0.000133
> trk layer 0 phisize > 1 RMS: 0.000143
> trk layer 1 phisize = 1 RMS: 0.000110
> trk layer 1 phisize > 1 RMS: 0.000123
> trk layer 2 phisize = 1 RMS: 0.000124
> trk layer 2 phisize > 1 RMS: 0.000134
>
> In general we see a residual width fo ~1.2 micron. The error assigned by the MVTX clusterizer is ~2.6 micron.
> How is this possible? the pixel pitch of the MVTX is ~30um and the intrisic resolution according to ALICE specs should be ~5um.
> Especially for phi size  = 1 clusters we should see something like 30/sqrt(12) ~ 9um
>
> Does anybody have an idea how to make sense of this?
>
> Thanks
>
>      Christof
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