Difference: DecayTreeFitter (8 vs. 9)

Revision 92010-11-03 - unknown

Line: 1 to 1
 
META TOPICPARENT name="LHCbComputing"

Decay-tree-fitter

Line: 33 to 33
 ctaudtf=dtf.fitParams().ctau().value()
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It may happen that a candidate has been reconstructed with the wrong PID, and a mass-constrained fit will give wrong results. A well known example is the Ds that is given the PID of a D+ in StdLooseDplus. This can be fixed by changing the PID before fitting.
    #correct pid if it is a Ds that has been called D+
    for d in cand.daughters():
      if abs(d.particleID().pid())==411:
        nK=0
        for dd in d.daughters():
          if abs(dd.particleID().pid())==321:nK=nK+1
        if nK==2:
          if d.particleID().pid()==411:d.setParticleID(gbl.LHCb.ParticleID(431))
          if d.particleID().pid()==-411:d.setParticleID(gbl.LHCb.ParticleID(-431))
 

Extracting the lifetime of a long-lived daughter

As an example consider the decay B+->D0 pi, with D0 -> K pi. Suppose that you are interested in extracting the decay length of the D0 meson. Given a pointer to the B+ particle, you can obtain the D0 decay length as follows:

 
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