TWiki> LHCb Web>LHCbTrackingEfficiencies>Velo2Long (revision 6)EditAttachPDF
Method for the determination of hadronic tracking efficiencies using partially reconstructed charm decays.

People involved: Mika Vesterinen, Laurent Dufour, Jeroen van Tilburg, S. Hellesund, D. Mueller.


The latest version of the note can be found at


All code is available on GitLab in the "AsymmetryTools" subproject of semileptonics. In there there is the "Velo2Long" in "projects".

In order to compile:

(checkout the project)
cmake .
make install

Earlier documentation

"Measuring pion and kaon tracking efficiencies and asymmetries using charm decays with one partially reconstructed track" (S. Hellesund) LHCb-INT-2014-041

"Measurement of the Kaon Detection Asymmetry using Double-tagged Partially Reconstructed D0 Decays" (D. Mueller) LHCb-INT-2013-054

Data samples

* Location: /eos/lhcb/user/l/ldufour/Velo2Long contains (2012, 2015) 4-body and (2015, 2016) 2-body samples.

Monte Carlo samples

Large MC samples to be generated a.s.a.p.

BKK paths:


  • 27163003: 2012 conditions, Pythia 6 & 8, 2-body mode, DecProdCut
    • sim08a: evt+std://MC/2012/27163003/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08a/Digi13/Trig0x409f0045/Reco14a/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 3.5M events
    • sim08e: evt+std://MC/2012/27163003/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08e/Digi13/Trig0x409f0045/Reco14a/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 140k events
    • sim08h: evt+std://MC/2012/27163003/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08h/Digi13/Trig0x409f0045/Reco14c/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 1M events
    • sim09a: evt+std://MC/2012/27163003/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim09a/Digi13/Trig0x409f0045/Reco14c/Stripping20NoPrescalingFlagged 1M events

  • 27163008: 2012 conditions, Pythia 6 & 8, 2-body mode, TightCut
    • sim08a: evt+std://MC/2012/27163008/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08a/Digi13/Trig0x409f0045/Reco14/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 2M events
    • (the other one is stripping filtered)

  • 27265000: 2012 conditions, Pythia 6 & 8, 4-body mode, DecProdCut (low statistics?)
    • sim08a: evt+std://MC/2012/27265000/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08a/Digi13/Trig0x409f0045/Reco14a/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 1.3M events


  • 27163400: 2012 conditions, Pythia 8, DecProdCut, mode: K pi pi0
    • sim08f: evt+std://MC/2012/27163400/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08f/Digi13/Trig0x409f0045/Reco14a/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 5M events
  • 27173001: 2012 conditions, Pythia 8, DecProdCut, mode: K mu nu (semileptonic D decay)
    • sim08d: evt+std://MC/2012/27173001/Beam4000GeV-2012-MagDown-Nu2.5-Pythia8/Sim08d/Digi13/Trig0x409f0045/Reco14a/Stripping20NoPrescalingFlagged/ALLSTREAMS.DST 2.5M events

Overall structured flow paper

Task Order CompletedSorted ascending Link to .pdf
Fit model 2 No -
Resolution and bias studies 2 No -
Raw asymmetry and efficiency dependencies 3 No -
VELO efficiency determination 4 No -
Comparison with other methods 4 No -
Comparison to Monte Carlo 5 No -
Projected results and conclusion 5 No -
Selection 1 Ongoing -

Todo list

  • Generate MC samples for background and signal.
  • Create OVERLAP functor taking ChildSelector arguments.
  • Verify that the MatchLong efficiencies are the same as the StdAllNoPIDPions container
  • Verify the L0 GLOBAL TIS condition for the 2016 data set.
  • Run anti-isolation for the 2-body mode.
  • Run a toy study: is there a bias in the actual momentum from the DTF?
  • Plot the momentum resolution from DTF.
  • Actually get the VELO efficiencies in.
  • Create pointing mass functor (desirably taking ChildSelector arguments).
  • Find out the anomalous asymmetry for very low momentum pions.
  • Fit in bins of nTracks in one fixed bin of momentum

Earlier presentations

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Topic revision: r6 - 2017-01-13 - LaurentDufour
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