11/24/03  AN    B_d oscillations  

used B=> muon D* sample from  the lifetime ratio analysis.  B => muon D0 candidates use "standard B+ particles" as defined in AA package. D* candidates require a pion with right charge correlation and best B0 vertex fit. the samples correspond to about 45 pb-1.

this is D0 mass peaks in two channels Kpi and Kpipi0 (pi0 is lost of course).



this is D*-D0 mass difference for Kpi channel. Slow pion has the following selections :  1) correct sign correlation with muon from B; 2) gives best B vertex.  in principle 2) should be studied and optimized - i am not sure this is the best we can do.



 this is D*-D0 mass difference for Kpipi0 channel, m (K pi) < 1.75 GeV.



this is m(K pi) distribution for D* candidates selected as m(D*)-m(Kpi) < 0.155 MeV. one can see a broad region with m(Kpi) < 1.75 GeV contributes to the D* signal. we need K pi pi0 MC to understand better this shape.


the blue histogram is the same as above, the open histogram is all events as in the plot on the top of this page.
 


Opposite side muon tagging 

first let's see what are those OS muons. using D0 -> Kpi sample with D* removed which is enriched with B+.

this is cos(3D angle between B candidate and tag muon). Pt muon > 2.5 GeV and use any muon (even nseg=0). there is a lot of muons collinear with B.




this is cos(Delta Phi between B candidate and tag muon). Pt muon > 2.5 GeV and use any muon (even nseg=0). there is a lot of muons collinear with B  and  also back to back muons.




this is cos(3D angle between B candidate and tag muon). Pt muon > 2.5 GeV and muon NOT from the same jet as B. no nseg cut. Jet definition uses Durham algorithm. as expected a lot of muons collinear with B dissapeared.

this is cos(Delta Phi between B candidate and tag muon). Pt muon > 2.5 GeV and muon NOT from the same jet as B. no nseg cut. Jet definition uses Durham algorithm. as expected a lot of muons collinear with B dissapeared. now most of the muons come from 180 degrees away jets or whatever is there.



this is distribution on nseg. this uses tagged D* sample but the distribution is very similar for tagged muons in any sample.



this is cos(3D angle between B candidate and tag muon). Pt muon > 2.5 GeV and muon from any jet but with nseg>1 required. almost all muons collinear with B dissapeared. hmmm. nseg>1 muons are very close to "tight muons" as defined by muon ID group.



this is cos(Delta Phi angle between B candidate and tag muon). Pt muon > 2.5 GeV and muon from any jet but with nseg>1 required. almost all muons collinear with B dissapeared.



this is eta of B->D* mu. apparently the acceptance is limited by CFT. Most likely comes from L3 tracking and may be CTT at L1.


more on the 'muon from B' eta. since tagged events may come from dimuons triggers one expects more eta coverage for them (because dimuon triggers do not require L3 tracking). however fraction of events with |eta|>1.5 grew only from 13% to 15.5% for "all events" and "tagged events" respectively.



this is eta of tag muon for 3 cases. tag muon has a mild requirement # CFT hits > 0 and # SMT hits > 0. one can see that we have tags in the full coverage of the muon system |eta| < 2. good news! one can also see that nseg=0 muons come mostly in the central region - why?


see this link for more about muon eta coverage using unbiased Jpsi sample.


this is Pt of tag muons for all and nseg>0 muons. apparently  nseg=0  muons  have some threshold  at 3 GeV.


this is Pt of all tag muons in tagged D* sample.



so regarding the tag muons i see two options :

1) use for tagging only "tight muons"
  a)  any tight muon
  b)  NOT from the same jet muon
  c)  require Delta Phi separation from B candidate
2) use any quality muons with some Delta Phi cut. here of course we'll take a hit in dilution because some of the nseg=0 muons are in fact just MIPs in the away jet. but the efficiency will be higher.

i like Delta Phi cut because it seems to give a cleaner separation for away jets.

We compared several tagging algorithms
1) any extra muon with max Pt. Later apply various selections like Pt cut, nseq cut, not from the same jet requirement, not from J/psi requirement. Re J/psi removal - this is a very small effect (~10E-4).
2) extra muon with max Pt not from the same jet. Of course, there is a considerable correlation with 1)

as said above the tagging has been tuned for B+ enriched sample :  D0(->Kpi) muon with removed D* candidates.  # of events was determined by fitting the mass peak (=> background subtracted). Table below summarizes the findings :
tagging
 total D0
 OS tag
 SS tag
 e=(OS+SS)/total
 D=(OS-SS)/(OS+SS)
 e*D^2
1), no Pt cut
 15252
 2355
 1483
 25.2+-1.4%
 22.7+-1.7%
 1.13+-0.18%
1) + Pt > 2.0 GeV
 15252 1887
 1069
 19.4
 27.7
 1.48
1) + Pt > 2.5 GeV 15252 1640
 884
 16.6
 29.9
 1.48
1) + Pt > 3.0 GeV 15252 1451
 749
 14.4
 31.9
 1.47
1) + Pt > 4.0 GeV
 15252
 848
 463
 8.6
 29.8
 0.74
1) + Pt >2.0 GeV; cos (B mu)<0.8
15252
 1067
 748
 11.9
 17.6
 0.36
2) + Pt > 2.0 GeV
 15252
 1206
 848
 13.5
 17.4
 0.41
1) + Pt > 2.0 GeV; nseg>1
 15252
 550
 372
 6.1
 19.3
 0.23
1) + Pt > 2.5 GeV, nsegt>1, fit 1
 15252 468
 316
 5.1%
 19.3%
 0.19%
1) + Pt > 2.5 GeV, nsegt>1, fit 2
15252
 468
 240
 4.6%
 32.2%
 0.48%
1) + Pt > 2.5 GeV, nsegt>0 15252
 726
 410
 7.5
 27.8
 0.57
1) + Pt > 3.0 GeV, nsegt>0 15252
 583
 282
 5.7
 34.7
 0.68
1) + Pt > 3.0 GeV, nsegt>0, cos (B mu)<0.8 15252
 551
 278
 5.4
 32.9
 0.59
1) + Pt > 3.5 GeV, nsegt>0 15252
 487
 264
 4.9
 29.6
 0.43
1) + Pt > 4.0 GeV, nsegt>0 15252
 388
 217
 4.0
 28.1
 0.31
 



now let's look at B vertices. use D* sample, no tagging required.
may be it is a good idea to use some fiducial cut, for example Decay length < 1 cm.


may be have Error <500 um cut

this is correlation between Decay Length and its Error. note that there is a suspicious region Error<40 um. it looks like those are D* muon vertices which coincide with PV.


list of fiducial cuts used in the below: Lxy B < 1 cm, error 40 um < Lxy B < 500 um

K-factors are discussed in detail here. k = 0.85 is a good starting pont.

this is dilution = (OS-SS)/(OS+SS) for the B+ sample (as before this is D0 sample with D* candidates removed)
tag 1), Pt cut 2.5 GeV, nseg tag >0. no k-factor applied



tag 1), Pt cut 3.0 GeV, nseg tag >0. no k-factor applied


tag 1), Pt cut 2.5 GeV, nseg tag >0, cos ( phi [B, tag muon]) < 0.8. no k-factor applied.



Dilution in B+ -> J/psiK+ sample

Phi and Theta angles between direction of B and tag muon. points are OS cases, histogram is SS cases. Muons are very close to 'tight muon' definition with Pt > 2 GeV, Ptot > 3 GeV. Dilution is 52%. efficiency 5.2%, eD2 = 1.4%



this is Asymmetry for B0 sample for tag 1), Pt cut 2.5 GeV, nseg tag >0. no k-factor applied.

 

if i require Lxy B > 1 mm (to check how a lifetime cut bias the asymmetry) we have this comparison. it seems the bias exists indeed.


below i compare asymmetry for 2 cases : 1) i fit D* signal and background to get # of OS and SS D* events. since the statistics is low the fit is not good sometimes. 2) i count # of events for m(D*)-m(Kpi) < 0.149 GeV. this uses the fact that the background is very small and in the first approximation could be neglected. the comparison is nothing more than a check on how stable the result is. no k- factor applied.

Fit for tag muon : Pt > 2.5 GeV, nseg > 0


Counting for tag muon : Pt > 2.5 GeV, nseg > 0 (note this plot was already shown above)


Fit for tag muon : Pt > 3.0 GeV, nseg > 0


Counting for tag muon : Pt > 3.0 GeV, nseg > 0



Kpipi0 channel


12/8/2003 AN - after some work on the mass peak fitting:

this is asymmetry for D0 -> K pi pi0 channel.  the proper lifetime is corrected by 0.85 to account for the difference of k-factors wrt Kpi channel. no k-factor applied.
Selections for the tag muon : Pt > 2.5 GeV and nseg > 0.


Selections for the tag muon : Pt > 3 GeV and nseg > 0.


Selections for the tag muon : Pt > 2.5 GeV and nseg > 1.


Selections for the tag muon : Pt > 3 GeV and nseg > -1. it looks like nseg=0 muons do not do any good..