Run 2 Turbo PV refitting bug

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* 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.

The initial investigation by Alex is here.

The same applies to lines that should have requested PV refitting but didn't, but these aren't discussed here.

The effect

If one or more tracks from your signal candidate are included in the PV fit, this will pull the position of the PV towards those tracks and so will bias any displacement variables calculated wrt the PV. This is particularly important for time dependent analyses, as the decay time will be biased. This could potentially bias measurements of, eg, lifetimes, mixing, time dependent CPV.

Mitigating effects

The PV fit only includes tracks with $\mathrm{IP} \chi^2 < 9$ (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.

Unaffected lines

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

For all these lines, PV refitting is only requested for the $D^0 \rightarrow h h $ part of the decay tree. If you access the PV for the $D^*$ or $\Xi_{cc}$ then you'll get the non-refitted PV.

Line
Hlt2CharmHadD02KmPipTurbo
Hlt2CharmHadDstp2D0Pip_D02KmKpTurbo
Hlt2CharmHadDstp2D0Pip_D02KmKp_LTUNBTurbo
Hlt2CharmHadDstp2D0Pip_D02KmPipTurbo
Hlt2CharmHadDstp2D0Pip_D02KmPip_LTUNBTurbo
Hlt2CharmHadDstp2D0Pip_D02KpPimTurbo
Hlt2CharmHadDstp2D0Pip_D02KpPim_LTUNBTurbo
Hlt2CharmHadDstp2D0Pip_D02PimPipTurbo
Hlt2CharmHadDstp2D0Pip_D02PimPip_LTUNBTurbo
Hlt2CharmHadXiccp2D0PpKmPim_D02KmPipTurbo
Hlt2CharmHadXiccp2D0PpKmPip_D02KmPipTurbo
Hlt2CharmHadXiccp2D0PpKpPim_D02KmPipTurbo
Hlt2CharmHadXiccpp2D0PpKmPimPip_D02KmPipTurbo
Hlt2CharmHadXiccpp2D0PpKmPipPip_D02KmPipTurbo
Hlt2CharmHadXiccpp2D0PpKpPimPip_D02KmPipTurbo

Affected lines

These are lines that requested PV refitting in some way, but did it incorrectly. Many of these include some $\mathrm{IP} \chi^2$ cuts, which will mitigate the effect, so these are also listed.

Line $\mathrm{IP} \chi^2$ cuts
Hlt2CharmHadDpToKmKpKpTurbo {'Hlt2CharmHadD2HHH_DpToKmKpKpCombiner': ['MIPCHI2DV(PRIMARY) > 4.0', 'AHASCHILD((MIPCHI2DV(PRIMARY)) > 10.0', 'ANUM(MIPCHI2DV(PRIMARY) > 4.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDpToKmKpPipTurbo {'Hlt2CharmHadD2HHH_DpToKmKpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDpToKmPipPipTurbo {'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadD2HHH_DpToKmPipPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2']}
Hlt2CharmHadDpToKmPipPip_ForKPiAsymTurbo {'Hlt2CharmHadSharedNoPIDDetachedChild_piFilter': ['MIPCHI2DV(PRIMARY) > 3.0'], 'Hlt2CharmHadDetAsym_DpToKmPipPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 100.0', 'MIPCHI2DV(PRIMARY) > 25.0', 'ANUM(MIPCHI2DV(PRIMARY) > 49.0) >= 2'], 'Hlt2CharmHadSharedNoPIDDetachedChild_KFilter': ['MIPCHI2DV(PRIMARY) > 3.0']}
Hlt2CharmHadDpToKmPipPip_LTUNBTurbo {}
Hlt2CharmHadDpToKpKpPimTurbo {'Hlt2CharmHadD2HHH_DpToKpKpPimCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_TightKFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDpToKpPimPipTurbo {'Hlt2CharmHadD2HHH_DpToKpPimPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDpToPimPipPipTurbo {'Hlt2CharmHadD2HHH_DpToPimPipPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToKmKpKpTurbo {'Hlt2CharmHadD2HHH_DspToKmKpKpCombiner': ['MIPCHI2DV(PRIMARY) > 4.0', 'AHASCHILD((MIPCHI2DV(PRIMARY)) > 10.0', 'ANUM(MIPCHI2DV(PRIMARY) > 4.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToKmKpPip {'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadD2HHH_DspToKmKpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToKmKpPipTurbo {'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadD2HHH_DspToKmKpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToKmKpPip_LTUNBTurbo {}
Hlt2CharmHadDspToKmPipPipTurbo {'Hlt2CharmHadSharedDetachedDpmChild_TightKFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadD2HHH_DspToKmPipPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToKpKpPimTurbo {'Hlt2CharmHadD2HHH_DspToKpKpPimCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToKpPimPipTurbo {'Hlt2CharmHadD2HHH_DspToKpPimPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDspToPimPipPipTurbo {'Hlt2CharmHadD2HHH_DspToPimPipPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 50.0', 'MIPCHI2DV(PRIMARY) > 4.0', 'ANUM(MIPCHI2DV(PRIMARY) > 10.0) >= 2'], 'Hlt2CharmHadSharedDetachedDpmChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDstp2D0Pip_D02KS0KS0_KS0DDTurbo {'Hlt2CharmHadDstp2D0Pip_D02KS0KS0_KS0DDTurboCombCombiner': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadDstp2D0Pip_D02KS0KS0_KS0LLTurbo {'Hlt2CharmHadDstp2D0Pip_D02KS0KS0_KS0LLTurboCombCombiner': ['MIPCHI2DV(PRIMARY) > 9.0'], 'Hlt2SharedKsLLTFKsLLTF': ['MIPCHI2DV(PRIMARY)>36']}
Hlt2CharmHadDstp2D0Pip_D02KS0KS0_KS0LL_KS0DDTurbo {'Hlt2CharmHadDstp2D0Pip_D02KS0KS0_KS0LL_KS0DDTurboCombCombiner': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2SharedKsLLTFKsLLTF': ['MIPCHI2DV(PRIMARY)>36']}
Hlt2CharmHadLcpToPpKmKpTurbo {'Hlt2CharmHadLcXic2HHH_LcpToKmPpKpCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadLcpToPpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadLcpToPpKmPip_LTUNBTurbo {}
Hlt2CharmHadLcpToPpKpPimTurbo {'Hlt2CharmHadLcXic2HHH_LcpToPimPpKpCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2'], 'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadLcpToPpPimPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToPimPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadXic0ToPpKmKmPipTurbo {'Hlt2CharmHadXic0ToPpKmKmPipTurbo_DetachedHHHHCombinerCombiner': ['ANUM(MIPCHI2DV(PRIMARY) > 6.0) >= 2', 'AHASCHILD((MIPCHI2DV(PRIMARY)) > 8.0', 'MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadXic0ToPpKmKmPip_LTUNBTurbo {}
Hlt2CharmHadXiccp2LcpKmPim_Lcp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccp2LcpKmPip_Lcp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccp2LcpKpPim_Lcp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccp2XicpPimPim_Xicp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccp2XicpPimPip_Xicp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccpp2LcpKmPimPip_Lcp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccpp2LcpKmPipPip_Lcp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccpp2LcpKpPimPip_Lcp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXiccpp2XicpPim_Xicp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadXiccpp2XicpPim_Xicp2PpKmPipTurboCombCombiner': ['MIPCHI2DV(PRIMARY) > -1.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0']}
Hlt2CharmHadXiccpp2XicpPip_Xicp2PpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadXiccpp2XicpPip_Xicp2PpKmPipTurboCombCombiner': ['MIPCHI2DV(PRIMARY) > -1.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}
Hlt2CharmHadXicpToPpKmPipTurbo {'Hlt2CharmHadSharedDetachedLcChild_piFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_pFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadSharedDetachedLcChild_KFilter': ['MIPCHI2DV(PRIMARY) > 4.0'], 'Hlt2CharmHadLcXic2HHH_LcpToKmPpPipCombiner': ['AHASCHILD((MIPCHI2DV(PRIMARY)) > 16.0', 'MIPCHI2DV(PRIMARY) > 6.0', 'ANUM(MIPCHI2DV(PRIMARY) > 9.0) >= 2']}

Systematic checks

If you care about PV refitting and you're using an affected line:

  • Firstly, check the $\mathrm{IP} \chi^2$ distribution of the tracks in your data. If their minimum values are all > 9 then you should be safe.
  • If you have full DST MC for your analysis you can check if the daughter tracks are ever included in the PV fit. Note that the PVs are constructed from HLT1 fitted VELO tracks, so you'll have to unpack these tracks and compare by LHCbIDs to your signal tracks. You can also evaluate the effect of refitting the PVs excluding signal tracks.
  • Try tightening the displacement cuts ($\mathrm{IP} \chi^2$, $\mathrm{FD} \chi^2$, decay time, etc) in your selection and examine how your results vary.
  • Apply a cut on PV n. tracks and vary its value. The greater the number of tracks in the PV, the less influence your signal candidate will have on the PV.

Possible workaround

It may be possible to approximate a PV refit by subtracting the contribution of a track from the PV. To be investigated. The caveats here are:

  • The signal track will need to be refitted as an HLT1 VELO track to recover the track as it was used in the PV fit.
  • If the refitted track has $\mathrm{IP} \chi^2 < 9$ it can be assumed to have been used in the PV fit, however, this will likely not be exact and could induce other biases.
  • Even if the refitted PV can be recovered, any cuts will still have been applied wrt the non-refitted PV which will affect, eg, efficiency vs decay time.

-- MichaelAlexander - 2019-06-19

Edit | Attach | Watch | Print version | History: r4 < r3 < r2 < r1 | Backlinks | Raw View | Raw edit | More topic actions...
Topic revision: r2 - 2019-06-19 - MichaelAlexander
 
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    LHCb All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2019 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback