sPHENIX tracking discussion

[Hugo Pereira Da Costa <hugo.pereira-da-costa AT cea.fr>]

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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