1. Recent D0 results on Quarkonium
(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)

2. Tevatron & DØ RunII com: 1.96 TeV PPbar lumi: 2E32 cm-2s-1
Main Injector
(new)
Tevatron DØ
CDF
Chicago 
p source
Booster
com: 1.96 TeV PPbar
lumi: 2E32 cm-2s-1
Xing: 396 ns

4. - good tracking, vertex, impact parameter measuring performance
- Silicon Microvertex Tracker (SMT) + Central Fiber Tracker (CFT) + 2T Solenoid
- good tracking, vertex, impact parameter measuring performance
Pseudo rapidity: h = -ln(tg(q/2))
Spatial separation: △R2=△f2+△h2

6. Muon system: - 3 layer, 1 layer (A) in 1.8T Toroid - Good coverage:
central |h|<1
forward 1<|h|<2
- Muon-Tracking match  muon candidate
- fast and efficient Di-Muon Trigger

7. The observation of X(3872)  J/y(m+m-) p+p-

8. First observed
confirmed

9. Events Selection: m+m- from J/y - Apr 02 – Jan 04, ~230pb-1
- di-muon triggered
- 2 well identified muon tracks, opposite charged
＜ M(m+m-) ＜ 3.35 GeV/c2
- pT(m+m-) ＞ 5 GeV/c2
- 2 opposite charged tracks, with spatial separation as
△R(J/y p+p-, each p) ＜ 0.4
- pT(p) ＞ 0.7 GeV/c2
- M(p+p-) ＞ 0.52 GeV/c2
- A good (m+m-p+p-) Vertex, c2 <16 for 5 degree of freedom,
i.e. 4 tracks from the same vertex
- ≤100 tracks in the event
m+m- from J/y
add ”p+p-” tracks

10. 522 ± 100 - fitted width 17 ± 3 MeV/c2 After CUT Results:
- Use mass difference (to J/y) for
better resolution
△M = M(m+m-p+p-) – M(m+m-)
- data fit:
y(2S), Gaussian (solid)
X(3872), Gaussian (solid)
background, 3rd order polynomial
(dashed)
- X(3872) candidates
522 ± 100
- mass difference
774.9 ± 3.1(stat) ± 3.0(syst) MeV/c2
- fitted width
17 ± 3 MeV/c2
Results:

11. X(3872) production and decay property studies:
split data into two sub-samples with production variables:
a) pT(J/ypp) :
- pT＜15 GeV
- pT＞15 GeV
b) Rapadity:
- |y|＜1 (central)
- 1＜|y|＜2 (forward)
d) xy decay length dl
(“prompt” or from B-decay):
- dl＜100 mm
- dl＞100 mm

12. spliting with decay variables:
c) Helicity Cos(qp), i.e.
boost X and one of pions into di-pion rest frame and measuring the open angle:
- Cos(qp)＜0.4
- Cos(qp)＞0.4
f) Helicity Cos(qm), i.e.
boost X and one of muons into di-muon rest frame and measuring the open angle:
- Cos(qm)＜0.4
- Cos(qm)＞0.4
e) Isolation, i.e.
the ratio of X momentum to the sum of all tracks’ momentum in Cone 0.5 to X:
- iso ＝1 , “isolated”
- iso ＜1

13. Calculate the ratio of one sub-sample to the total , eg N|y|＜1:Ntotal
For production/decay variables:
Calculate the ratio of one sub-sample to the total , eg N|y|＜1:Ntotal
Then compare X distribution with y(2S) benchmark
pT > 15 GeV
|y| < 1
Cos(qp) < 0.4
Cos(qm) < 0.4
isolated
dl < 0.01cm
The properties of production and decay of X(3872) appears consistent with y(2S) within errors

14. - Charmonium? “meson-molecule” ?
What’s the X(3872)
- Charmonium?
L-excited multiplet splits much more than expected by assuming Coulomb-Scalar confinement
“meson-molecule” ?
M(D-+D*+)=3879.5±0.7MeV
M(D0+D*0)=3871.5±1.0MeV (coincident?)
appears unexpectedly narrow

15. Summary of X(3872):
Confirm the existence of X(3872) with mass difference
△M = M(X) – M(J/y) = ± 3.1(stat) ± 3.0(syst) MeV/c2
- (522±100) 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
search for charged analog, X+J/yp+p0
search for radiative decays
Next step:

16. The observation of Bc  J/y(m+m-) m+nm

17. Bc -- last of ground state of meson
- Theory predictions: [1] C.Chang et al, PRD49(1994) [2] E.Ebert et al, hep-ph/ ; PRD68(2003) MBc ~ 6.4 GeV tBc ~ ps
-- ct~100mm, significantly shorter than B
Bc±  J/y(m+m-) m± n
-- Br~2.4% + trilepton final state + easy to trigger
- The only previous evidence by CDF RunI

18. Events Selection: - 210pb-1 data - di-muon triggered
- M(m+m-) within 0.25 GeV of J/y
- a third track (pT>1.5) with best common vertex fit to J/y(mm) :
“J/y+1 track” data control sample
- The third “+1” track should be muon, with M(J/ym) ＜8 GeV
after Selection:
due to missing neutrals, the select samples are polluted by background severely
use (ym) invariant mass and pseudo proper time distributions to fit

19. Background shape (data):
use J/y+1 track control data sample
divided into 2 subsets:
1) “prompt” J/y
2) “heavy flavor” one from B decay
cross-checked with
y(2S) + 1 track bkg dominated data
±0.34 GeV
+0.14
-0.13
Bc mass log likelihood
Signal shape (MC):
- MC templates of MBc 5.5 – 6.7 with
0.1GeV interval
- Full detector smearing + Selection
Bc Fit:
extract signal from a combined unbinned likelihood fit to J/ym invariant mass and proper time

20. With significance SB in excess of
“Floating” fit signal + bkg distributions:
Signal ±11.8
Total
Prompt
Heavy F
Number of events
With significance SB in excess of
5 standard deviations

21. - check excess consistency with data
Consistency check:
Simple counting analysis
- normalize background J/y+1 track sample to selected sample with T>2
- check excess consistency with data
Fit w/o signal
D2log(likelihood)=60 for 5 degrees of freedom

22. Systematic uncertainties:

23. Bc b c Something else: Test Probability of extra m within f±90°:
The associated c-quark likely results in
a charmed hadron proximity to the Bc
charmed mesons decay
semileptonically occasionally
Test Probability of extra m within f±90°:
- J/y+1 track background control sample, 1%
- Selected Bc candidates, 5 out of 108, 5±2%

24. Preliminary results on Bc with significantly more statistics
Summary:
Preliminary results on Bc with significantly more statistics
Events: 95 ± 12±11
Mass: ±0.34 GeV/c2
+0.14
-0.13
Lifetime: ±0.121 ps
+0.123
-0.096

25. The production of Upsilon(1S)

26. Theory modeling of production:
factorized QCD calculations to O(a3) currently employed by Pythia - color-singlet, color-evaporation, color-octet models
U(1S) Tevatron:
50% produced promptly, i.e. at primary vertex and relatively isolated - 50% from excited states radiative decay
Event selection:
luminosity: ± 10.3 pb-1 - di-muon: pT>3, tight Tracking and Calorimeter isolation cut - invariant mass in 7 – 13 GeV

27. Data sample partition:
U’s |y| 
U‘s PT 
Data sample partition:
- Dy1: 0 ＜ |yU| ＜ Dy2: 0.6 ＜ |yU| ＜ Dy3: 1.2 ＜ |yU| ＜ 1.8
Sample fit:
- Background: 3rd order polynomial - U(1,2,3S) resonances: double Gaussian - the mass and width of U(1S) are free parameters; others are fixed relative to the mass

28. Evaluating the U(1S) Production Xsec:
with eff in different rapidity region:
The measured cross-section×BR(U(1S)mm) is as

29. - No strong dependence on rapidity observed
749±20±75
781±21±78
598±19±56
with 6% luminosity uncertainty

30. Run2 preliminary results consistent with CDF Run1

31. measurements of U production at D0 to 1.8 rapidity region
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 RunI’s
- CDF √s=1.8TeV, |y|<0.4, ds/dy*Br =680±15±18±26 pb
- D0 √s=1.96TeV, |y|<0.6, ds/dy*Br =749±20±75±49 pb
- PYTHIA predict a factor of 1.11 from 1.8 to 1.96 TeV

32. Thank you!