Difference: TurboPVRefittingBug (3 vs. 4)

Revision 42019-06-25 - MichaelAlexander

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META TOPICPARENT name="Run12Performance"
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Run 2 Turbo PV refitting bug

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Run 2 Turbo PV refitting issue

 

The issue

In order to obtain an unbiased (or less biased) measure of the displacement of a particle wrt a PV (eg, flight distance, decay time, etc), PVs must be refitted excluding the signal tracks. This is enabled by setting ReFitPVs = True on the appropriate algorithm (CombineParticles, FilterDesktop, etc). However, in order to trigger the generation of refitted PVs, the PVs must be accessed by the algorithm, eg, by a BPV

Changed:
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LoKi functor. When refitted PVs are generated, they are saved to the output mDST along with the particle $\rightarrow$ PV relations tables and so are accessible for user analysis. If the refitted PVs aren't generated, they can't be recovered offline on the mDST Turbo output.

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* LoKi functor. When refitted PVs are generated, they are saved to the output mDST along with the particle $\rightarrow$ PV relations tables and so are accessible for user analysis. If the refitted PVs aren't generated, they can't be recovered offline on the mDST Turbo output.
  The majority of Turbo lines requesting PV refitting in some algorithm in their sequence didn't do so in conjunction with a BPV functor, and so the refitted PVs aren't persisted, and are lost.
Line: 25 to 23
  The PV fit only includes tracks with $\mathrm{IP} \chi^2 &amp;lt; 9$ (see here and here). Thus, if you have strong enough displacement cuts ($\mathrm{FD} \chi^2$, $\mathrm{IP} \chi^2$, etc) in your selection, the signal tracks will never have been included in the PV fit anyway. Note however that there is a difference between the $\mathrm{IP} \chi^2$ used by the PV fitter to include/exclude tracks and the $\mathrm{IP} \chi^2$ that you'll get in your ntuples offline.
Changed:
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Unaffected lines

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Partially unaffected lines

  These are lines that requested PV refitting, and did so correctly. Lines that didn't request PV refitting aren't shown.
 
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