Sergey Burdin (Fermilab)

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B Lifetime and Mixing in

• Sergey Burdin (Fermilab)
• for the DØ Collaboration
• WIN03 / Lake Geneva, October 6-11, 2003

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Detector
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Tracker
Trigger muontrack covers ?lt1.8
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Image of Tracker from ?-conversions
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Tracking Performance (1)
Impact Parameter Resolution
Is not used yet for PID

• Can provide
• K/p separation for Ptotlt400 MeV
• p/p separation for Ptotlt700 MeV

s(DCA)53µm _at_ Pt1GeV and better _at_ higher Pt
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Tracking Performance (2)
? for kaons from D?D0p
Pt spectrum of soft pion from D?D0p

• Tracks are reconstructed
• in wide ? limits
• starting from Pt180 MeV

Efficient muon system tracker tracking give
us large sample of semileptonic B decays
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Large B Semileptonic Sample

• Muon
• Pt gt 2 GeV/c
• Ptot gt 3 GeV/c
• nSMT gt 1
• nCFT gt 1

• Charged tracks
• Pt gt 0.7-1 GeV/c
• Secondary Vertex
• Lxy / sL gt 4
• cos(?(L,PD))gt0.95

• no hadronic PID so far (except for D)

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History of the B Lifetime Measurements
Predictions
Report of the B Physics at the Tevatron Workshop
(12/2001)

• t(Bd)/t(Bs)10.01
• t(?0b)t(?b) lt t(Bd) lt t(?-b) lt t(Ob)
• G(?b)-G(?-b)0.110.03ps-1
• 0.9lt t(?b)/t(Bd) lt1

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B Lifetime from Inclusive B?J/? X

• Use J/??µµ- for tagging, vertex constraint, Pt
  determination
• Clean signal
• Large statistics
• Good vertex resolution
• Good momenta resolution

• Large prompt J/? contamination
• Need Pt correction factor from MC

Method
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B Lifetime from Inclusive B?J/? X
Corrections

LBxy LBxy PBt / PBt ctB?B LBxy/(ß?)t LBxy
MB/PBt (L?xy M?B/P?t )/ltF(P?t )gt
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B Lifetime from Inclusive B?J/? X
Results
Proper Decay Length Shape

• Background (19)
• GExp(t0)Exp(-t0) Exp(t1)Exp(-t2)cons
  t
• Shape from the J/? sidebands
• Signal (81)
• Prompt J/? (82) GExp(t0)Exp(-t0)
• J/? from b (18) Exp(tB)?G

Correction factor gives one of the major
contributions into the systematic errors
lttBgt1.5620.013(stat)0.045(syst) ps
BLWG lttBgt1.5730.008 ps
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B Lifetime from B?J/?K
Proper Decay Length Shape

• Background from B-sidebands
• G Exp(t1) Exp(-t2) Exp?G (BS
  contamination)
• Signal
• Exp?G

Fully reconstructed ? No Correction Factor!
lttBgt1.650.083(stat)0.123(syst) ps
BLWG lttBgt1.6520.014 ps
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Bd,S Lifetimes from B ? J/?K0,?
Similar kinematics ? Some systematic errors can
be cancelled in ratio !
Proper Decay Length Shape

• Background
• G Exp(t1) Exp(t2) Exp(-t3)
• Signal
• Exp(tB)?G

Results
Signal 10519
?Ldt114pb-1
Signal 6913
BLWG tBs/ tBd0.9380.035
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B Lifetime from Semileptonic Decays B ? D0µX
Benchmark measurement
?Ldt12pb-1
Proper Decay Length Shape

• Background
• G G Exp(t1)?2G Exp(-t2)?2G const
• Signal
• Exp?2G

ct LxyMbK/Pt(Dµ)
K Pt(Dµ) / PtB (from MC)
Result
tB 1.4600.083(stat.) ps
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B mixing

• ?M - difference between B0 mass eigenstates gives
  the oscillation frequency
• Need for ?M measurement
• Proper Decay Time
• Time evolution of flavor
• or time integrated rate (no CPV) r N(B0)/N(B0)
  x2/(2x2)
• x ?M / G ?M t
• Initial State Flavor Tagging (ISFT)
• efficiency e(NcorrNwrong)/(NcorrNwrongNnotag)
  
• dilution D(Ncorr-Nwrong)/(NcorrNwrong)
• Significance of mixing measurement S ? eD2
• Final State Flavor Tagging
• from decay products

.
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Bd,S mixing

• The Bd oscillation frequency is not too high
• Benchmark measurements
• Semileptonic B decays can be used for frequency
  measurements

?Md 0.502 ? 0.006 ps-1

• The BS oscillation frequency is very high ?MS gt
  14.4ps-1 (95CL)
• Good proper decay time resolution is needed for
  frequency measurements
• S ? exp(-(?MS st)2)
• Semileptonic BS 6-7k
  events/200pb-1

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ISFT Opposite Side Muon Tagging
B?J/?K

• PTµ gt 1.9 GeV
• Qµ charge of muon with the highest Pt
• Classification
• Qµ ! QK correct tag
• Qµ QK wrong tag
• No muon No tag

µ

• D (57.019.3)
• e (5.00.7)
• eD2 (1.61.1)

D0 RunII preliminary
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ISFT Opposite Side Jet Charge Tagging
B?J/?K

• Ptgt 0.5GeV
• ?ZPVlt2cm
• Classifications
• Qgt0.2 sign(Q) ! QK correct tag
• Qgt0.2 sign(Q) QK wrong tag
• Qlt0.2 no tag

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ISFT Same Side Tagging

• Excited B decays into B and pion/kaon which
  carries the initial state flavor information

Example Bd? Bp-
p
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Summary of Results

• B Lifetime measurements

Mode t,ps sstat ,ps ssyst ,ps ratios
Inclusive B?J/? X 1.562 0.013 0.045
B?J/?K 1.65 0.083 0.123
B ? J/?K0 1.51 0.19-0.17 0.20 tBs/tBd 0.790.14
BS ? J/?? 1.19 0.19-0.16 0.14 tBs/tBd 0.790.14
B ? D0µX 1.460 0.083 ------

• B Flavor Tagging

Mode e, D, e D2,
Jet Charge 46.72.7 26.76.8 3.31.7
Muon Tag 5.00.7 57.019.3 1.61.1
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Conclusion

• . has magnetic field and efficient tracker
  with large coverage
• . has and continues to collect large
  samples for B physics
• . has produced first results on B lifetime
  mixing measurements and much more excellent
  results are ahead

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Backup Slides
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Bd,S Masses (B ? J/?K0,?)
Cuts are not the same as for LT
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B0 ? J/?KS