Recent B Physics Results at D

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Recent B Physics Results at DØ

• Bill Lee
• Florida State University
• 18 February 2004

• X(3872)
• B Lifetime and Mixing
• Bs ? mm- Search

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The DØ Run 2 Detector
SMT
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X(3872) at D0

• Using 200 pb-1 of DATA collected April 2002
  September 2003, we look for X(3872) ? J/? pp-
• Silicon hit gt 1
• num tracks lt 100
• pT(J/?) gt 4 GeV/c
• 2.8 lt M(mm-) lt 3.4 GeV/c2
• pT(?) gt 0.4 GeV/c
• ?s within same cone as J/?
• M(?? -) gt 0.52 GeV/c2
• M(mm- ?? -) -M(mm-) lt 1.0 GeV/c2
• ?2 (mm- ?? - - vertex) lt 16
• zvertex lt 35 cm

4.4s effect
300 ? 61 X(3872) candidates
DM 0.7684 ? 0.0035 (stat) ? 0.0039 (sys) GeV/ c2
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Properties of X(3872)

• Are the production characteristics similar to
  the ?(2S)?
• To compare, the data was binned for several
  different variables decay-length,
  isolation, h (pseudo-rapidity), pT, and
  helicity of (?? -)

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X(3872) and ?(2S) comparison
Yield per given cut / Total Yield
Within the current statistical uncertainties, the
production of X(3872) has similar behavior as the
?(2S), but an exotic meson could also behave
similarly.
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Is X(3872) charmonia?

• If the charged analog X?J/?pp0 was observed,
  then cc hypothesis could be ruled out
• While observing radiative decays X???c1 would
  favor cc hypothesis
• Both of these would require DØ to identify low
  energy p0 and ? (work in progress)

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-
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Measuring Lifetime using B? J/? X, J/? ???-

• Use J/????- 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

114pb-1
?(2s) Signal 8.22K events Mass 3.668 0.002
GeV/c2 ? 0.071 0.002 GeV/c2
J/? Signal 290.3k events Mass 3.07180.0002
GeV/c2 ? 0.07410.0002 GeV/c2
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B Lifetime from Inclusive B?J/?X
B? J/? X
?Ldt?114 pb-1
F correction factor to use the pT(J/ ?) to
estimate the momentum of the B to find proper
time. Obtained from Monte Carlo
??? 1.564 ? 0.014 ps (PDG)
J/? from Bs 18
??? 1.562 ? 0.013 ? 0.045 ps
Correction factor leads to the major systematic
error
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Bd,s Masses (J/? K0,?,K0s)
For CP and Lifetime studies
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B Lifetime from B?J/?K
?Ldt?114 pb-1
Fully reconstructed?No Correction Factor!
lt?Bgt1.650.083(stat)0.123(syst) ps
lt?Bgt 1.6710.018 ps (PDG)
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Bd,s Lifetimes from B ?J/?K0,?
Similar kinematics?Some systematic errors can be
cancelled in ratio!
Signal 10519
Signal 6913
?Ldt?114 pb-1
?Bd1.510.19 (stat) 0.20(syst) ps
-0.17
PDG ?Bd 1.537 0.015 ps
?Bs1.190.19 (stat) 0.14(syst) ps
-0.16
PDG ?Bs 1.461 0.057 ps
?Bs/ ?Bd0.79 0.14
PDG ?Bs/ ?Bd 0.95 0.038
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Large B Semileptonic Sample

• Muon
• Pt gt 2 GeV/c

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

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B Lifetime from Semileptonic Decays B ? D0?X
We are able to measure Lifetime
?Ldt?12 pb-1
c? LxyMbK/Pt(D?)
K Pt(D?) / PtB (from MC)
?B 1.460 0.083 (stat) ps
?B 1.564 0.014 ps (PDG)
We will use this for mixing studies
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Mixing Flavor tagging

• In order to study Bs mixing we will need
• final state reconstruction
• ability to measure B decay lengths
• the ability to tag the flavor of the B at
  production and decay.
• We can use flavor-specific decays to get the
  flavor of the B at decay. To get the flavor of
  the B at production we use three methods
• - Soft-lepton tags
• - Jet Charge tag
• - Same Side tagging
• We can test these tools using our B data sample

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Flavour Tagging results
DØ RunII Preliminary
Method Based on B Signal Efficiency Dilution Tagging Power
Soft Muon 5 57
Jet Charge 47 27
Same Side 79 26
Muon DATA, we will also use electrons
Performance with B0/Bs is under study
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Search for Bs ? mm-
SM Br(Bs ? mm- ) 3.7 ? 10-9 Some SUSY
tan(b) models can enhance the signal.
MC
Dimuon spectrum
?Ldt?100 pb-1
No Excess Seen.
Br(Bs ? mm- ) lt 1.6 ? 10-6 at 90 CL
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Summary

• DØ has observed the X(3872) particle in 200 pb-1
  data
• We have reprocessed ? 200 pb-1 of data to better
  improve our analyses.
• D0 will be able to study Bs mixing
• Tevatron is performing well.
• D0 recorded 9.4 pb-1 last week.
• Lots of data.
• Many more interesting results coming very soon!