Recent D0 results on Quarkonium

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(commented by Rick Van Kooten D0 B-convener)
presenting D0 Collaboration
Recent D0 results on Quarkonium
HAN, Liang Univ. of Science Technology of
China Univ. of Manchester
- Tevatron D0 Run2 - X(3872) - Bc meson
- Upsilon(1S)
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Tevatron DØ RunII

• com 1.96 TeV PPbar
• lumi 2E32 cm-2s-1
• Xing 396 ns

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Tracking Vertex
- Silicon Microvertex Tracker (SMT) Central
Fiber Tracker (CFT) 2T Solenoid
- good tracking, vertex, impact parameter
measuring performance
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Muon system

- 3 layer, 1 layer (A) in 1.8T Toroid - Good
coverage central hlt1 forward
1lthlt2 - Muon-Tracking match ? muon candidate
- fast and efficient Di-Muon Trigger
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The observation ofX(3872) ? J/y(mm-) pp-
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Events Selection
- Apr 02 Jan 04, 230pb-1 - di-muon
triggered - 2 well identified muon tracks,
opposite charged - 2.80 lt M(mm-) lt 3.35 GeV/c2
- pT(mm-) gt 5 GeV/c2 - 2 opposite charged
tracks, with spatial separation as
?R(J/y pp-, each p) lt 0.4 - pT(p) gt 0.7
GeV/c2 - M(pp-) gt 0.52 GeV/c2 - A good
(mm-pp-) Vertex, c2 lt16 for 5 degree of
freedom, i.e. 4 tracks from the same vertex
- 100 tracks in the event
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X(3872) production and decay property studies
split data into two sub-samples with production
variables
a) pT(J/ypp) - pTlt15 GeV - pTgt15
GeV
b) Rapadity - ylt1 (central) -
1ltylt2 (forward)
d) xy decay length dl (prompt or from
B-decay) - dllt100 mm - dlgt100 mm
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spliting with decay variables
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• For production/decay variables
• Calculate the ratio of one sub-sample to the
  total , eg Nylt1Ntotal
• Then compare X distribution with y(2S) benchmark

The properties of production and decay of
X(3872) appears consistent with y(2S) within
errors
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Whats the X(3872)
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Summary of X(3872)

• Confirm the existence of X(3872) with mass
  difference
• ?M M(X) M(J/y) 774.9 3.1(stat)
  3.0(syst) MeV/c2

- (522100) candidates of signal are established
with 230 pb-1 data

• Selected production/decay properties of X(3872)
  are similar
• to those of y(2S) within error

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The observation ofBc ? J/y(mm-) mnm
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Bc -- last of ground state of meson
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due to missing neutrals, the select samples are
polluted by background severely
Events Selection
- 210pb-1 data - di-muon triggered - M(mm-)
within 0.25 GeV of J/y - a third track (pTgt1.5)
with best common vertex fit to J/y(mm)
J/y1 track data control sample - The third
1 track should be muon, with M(J/ym) lt8 GeV
after Selection

• use (ym) invariant mass and pseudo proper time
  distributions to fit

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Floating fit signal bkg distributions
With significance SB in excess of 5 standard
deviations
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Consistency check

• Fit w/o signal
• D2log(likelihood)60 for 5 degrees of
  freedom

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Systematic uncertainties
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Something else

• The associated c-quark likely results in
• a charmed hadron proximity to the Bc
• charmed mesons decay
• semileptonically occasionally

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Summary
Preliminary results on Bc with significantly more
statistics

• Events 95 1211

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The production of Upsilon(1S)
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Evaluating the U(1S) Production Xsec
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Summary
measurements of U production at D0 to 1.8
rapidity region

• The pT spectrum does not show significant
• difference in various rapidity region

• Results consistent with CDF RunIs
• - CDF vs1.8TeV, ylt0.4, ds/dyBr
  680151826 pb
• - D0 vs1.96TeV, ylt0.6, ds/dyBr
  749207549 pb
• - PYTHIA predict a factor of 1.11 from 1.8 to
  1.96 TeV

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Thank you!
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