Alberto S

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Heavy Flavor Physics at DØ

• Alberto Sánchez Hernández
• CINVESTAV (Mexico City)
• DØ Collaboration

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DØ Detector
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Tracker
SMT CFT ?max 1.65
82 CFT layers
SMT region ?max 2.5
? - ln (tan(?/2))
4 SMT layers
Trigger muontrack covers ?lt2.2
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Tracking Performance
Impact Parameter Resolution
SMT dE/dx
MC ? Data

• Can provide
• K/? separation for Ptotlt400 MeV
• p/? separation for Ptotlt700 MeV
• NOT yet used for PID

?(DCA)?53?m _at_ Pt1GeV and ?15 ?m _at_ higher Pt
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Tracking Performance
Data from semileptonic decays (B ? m D X)
? for kaons from D?D0?
pT spectrum of soft pion from D?D0?

• Tracks are reconstructed
• over a wide ? range
• starting from pT 180 MeV

Efficient muon and tracking system give us
a large sample of semileptonic B decays
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A New Particle X(3872)

• Last Summer BELLE announced a NEW particle
  around 3872 MeV/c2 when looking at B ? KX (X ?
  J/? pp-)
• possible charmonium state or an exotic meson
  molecule (?)
• BELLE didnt find evidence for ??c1

CDF II hep-ex/0312021
BELLE PRL91,262001,(2003)

• X(3872) ? J/? pp- production in ppbar
  collisions has been confirmed by CDF

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What can we say about the X(3872)?

• Using 200 pb-1 of DATA collected April 2002
  September 2003, we look for X(3872) ? J/? pp-
• SMT 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)

• Look if production characteristics are
  similar to ?(2S).
• Data was binned for different variables
  decay- length, isolation, h (pseudo- rapidity)
  pT, and helicity of (?? -)

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X(3872) - ?(2S) comparison
Yield given cut / Total Yield
Within the current statistical uncertainties, the
production of X(3872) has similar behavior as the
cc(bar) state ?(2S)
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What is X(3872)?

• If the charged analog X?J/?pp0 was observed,
  then cc(bar) hypothesis could be ruled out
• While observing radiative decays X???c1 would
  favor cc(bar) hypothesis
• Both of these would require DØ to identify low
  energy p0 and ? (work in progress)
• Our tests show production characteristics of
  X(3872) (in the used variables) seems similar to
  those from ?(2S) (within the statistical
  uncertainties), this would tend to favor a
  cc(bar) hypothesis, but we do not know (yet)
  how these characteristics look for an exotic
  meson-molecule (theoretical input needed).

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B Semileptonic Samples

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

For Mixing and Lifetime studies

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

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Bd,s Masses (J/? K0,?,K0s)
For CP and Lifetime studies
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B Lifetime Measurements
Report of the B Physics at the Tevatron Workshop
(12/2001)
Predictions

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

Experimental Results

• ?(B) 1.5730.008 ps
• ?(B0) 1.5340.013 ps
• ?(B) 1.6520.014 ps
• ?(B)/?(B0) 1.0810.015

• ?(BS) 1.4390.053 ps
• ?(bbaryon) 1.2100.051 ps
• ?(?b) 1.2330.078 ps

-0.076
B Lifetime Group (Summer 2003)
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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
? 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
?dt?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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B Lifetime from B?J/?K
?dt?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!
?dt?114 pb-1
Signal 10519
Signal 6913
?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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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
We will use this for mixing studies
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Mixing Flavour tagging

• Use flavour-specific decays to get flavour of B
  at decay. To get flavour of B at production use
• - Soft-lepton tags - High dilution power, low
  efficiency (SL decay of other B)
• - Jet Charge tag - Poorer dilution power, high
  efficiency (track-jet from other b quark)
• - Same Side tagging - Poorer dilution power,
  high efficiency (fragmentation, B)
• We test this tools using B data sample

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Opposite Side Muon Tagging

• PT? gt 1.9 GeV
• Q? charge of muon with
• the highest PT
• Classification
• Q? ! QK correct tag
• Q? QK wrong tag
• No muon No tag

B?J/?K
DØ RunII preliminary

• D (57.0 19.3)
• ? ( 5.0 0.7)
• ?D2 (1.6 1.1)

?
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Opposite Side Jet Charge Tagging
B?J/?K

• PT gt 0.5 GeV
• ?ZPV lt 2 cm
• Classifications
• Qgt0.2 sign(Q) ! QK correct tag
• Qgt0.2 sign(Q) QK wrong tag
• Qlt0.2 no tag

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Same Side Tagging

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

Example Bd ?B?-
?
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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, will also use electrons
Performance with B0/Bs is under study
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Search for Bs ? mm-
MC
?Ldt?100 pb-1
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
• Statistical significance of 4.4s
• ?M 0.7684 ? 0.0035 (stat) ? 0.0039 (sys)
• Data separated into various regions, we found
  similar behaviour as ?(2S), within statistical
  uncertainties
• Many other results as B physics program under way
• We have reprocessed ? 200 pb-1 of data to better
  improve our analyses
• A lot more interesting results very soon!

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More Data
Reprocessed ?Ldt?200 pb-1
?Ldt ?114 pb-1