Studies of opposite side muon tagging - which selections on OS tag muon can introduce bias to the mixing measurement?

let's start with a list of possible biases
1) Pt is conserved so a Pt cut on away muon can bias the Pt distribution of the tagged B. Bias in Pt may translate to bias in boost and therefore to bias in proper decay time. this effect may bias the time dependence of the dilution.
2) IP cut for tag muon can create bias for two reasons
    a) selection on the tag muon IP is effectively b-tagging of the away jet. this should increase dilution with no time dependence.
    b) case of Bd in away jet : Bd oscillates and the oscillation has time dependence - exactly what we want to observe with tagged B. selection on the tag muon IP is correlated with the decay length => with proper decay time. thus the tag muon IP cut may decrease dilution with no time dependence.       

now let's see if the above is supported by data. i used the same D0/D* sample  as for the Bd  oscillation analysis, see  this link

this is scatter plot of tag muon IP significance vs. proper decay length of tagged B0->mu D*. no apparent correlation is observed.


same as profile


this is profile of tag muon Pt vs proper decay length. no apparent correlation observed.



this is scatter plot of tag muon Pt vs. Pt of tagged B0->mu D*. no apparent correlation is observed.


same as profile



this is asymmetry (= dilution) for B+ -> mu D0 (-> Kpi)  for  two cases, see plot.  tag muon Pt >2.5 GeV, tag muon nseg > 0.



this is asymmetry (= mixing plot)  B0 -> mu D* ( -> pi D0 (-> Kpipi0))  for  two cases, see plot. tag muon Pt >2.5 GeV, tag muon nseg > 0.


in both cases above (B+ and B0) statistics is too low to reach unambiguous conclusions.

in any case i did not observe strong biases from selections on tag muon Pt or IP on the tagged B or Bd mixing measurement.

more to follow.