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)

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

- 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

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

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

First observed confirmed

Events Selection: m+m- from J/y - Apr 02 – Jan 04, ~230pb-1 - di-muon triggered - 2 well identified muon tracks, opposite charged - 2.80 ＜ 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

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:

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

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

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

- 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

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 - (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:

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

Bc -- last of ground state of meson - Theory predictions: [1] C.Chang et al, PRD49(1994)3399 [2] E.Ebert et al, hep-ph/0401237; PRD68(2003)094020 MBc ~ 6.4 GeV tBc ~ 0.3-0.5ps -- 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

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

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 5.95 ±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

With significance SB in excess of “Floating” fit signal + bkg distributions: Signal 95.5±11.8 Total 231 Prompt 66.0 Heavy F 69.5 Number of events With significance SB in excess of 5 standard deviations

- 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

Systematic uncertainties:

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%

Preliminary results on Bc with significantly more statistics Summary: Preliminary results on Bc with significantly more statistics Events: 95 ± 12±11 Mass: 5.95 ±0.34 GeV/c2 +0.14 -0.13 Lifetime: 0.448 ±0.121 ps +0.123 -0.096

The production of Upsilon(1S)

Theory modeling of production: factorized QCD calculations to O(a3) currently employed by Pythia - color-singlet, color-evaporation, color-octet models U(1S) Production @ Tevatron: 50% produced promptly, i.e. at primary vertex and relatively isolated - 50% from excited states radiative decay Event selection: luminosity: 159.1 ± 10.3 pb-1 - di-muon: pT>3, tight Tracking and Calorimeter isolation cut - invariant mass in 7 – 13 GeV

Data sample partition: U’s |y|  U‘s PT  Data sample partition: - Dy1: 0 ＜ |yU| ＜ 0.6 - Dy2: 0.6 ＜ |yU| ＜ 1.2 - 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

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

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

Run2 preliminary results consistent with CDF Run1

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

Thank you!