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

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

Pseudo rapidity:  ln(tg(  Spatial separation: △ R 2 = △  2 + △  2 Tracking & Vertex: - Silicon Microvertex Tracker (SMT) + Central Fiber Tracker (CFT) + 2T Solenoid - good tracking, vertex, impact parameter measuring performance

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

The observation of X(3872)  J/  (  +  - )  +  -

First observed confirmed

Events Selection: - Apr 02 – Jan 04, ~230pb -1 - di-muon triggered - 2 well identified muon tracks, opposite charged ＜ M(  +  - ) ＜ 3.35 GeV/c 2 - pT(  +  -  ＞ 5 GeV/c opposite charged tracks, with spatial separation as △ R(J/  +  -, each  ) ＜ 0.4  - pT(  ) ＞ 0.7 GeV/c 2 - M(  +  - ) ＞ 0.52 GeV/c 2 - A good (         ) Vertex,    for 5 degree of freedom, i.e. 4 tracks from the same vertex - ≤ 100 tracks in the event  +  - from J/  add ”  +  - ” tracks

After CUT - Use mass difference (to J/  ) for better resolution △ M = M(  +  -  +  - ) – M(  +  - ) - data fit:  (2S), Gaussian (solid) X(3872), Gaussian (solid) background, 3rd order polynomial (dashed) - X(3872) candidates 522 ± mass difference ± 3.1(stat) ± 3.0(syst) MeV/c 2 - fitted width 17 ± 3 MeV/c 2 Results:

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

c) Helicity Cos(   ), i.e. boost X and one of pions into di-pion rest frame and measuring the open angle: - Cos(   ) ＜ Cos(   ) ＞ 0.4 f) Helicity Cos(   ), i.e. boost X and one of muons into di-muon rest frame and measuring the open angle: - Cos(   ) ＜ Cos(   ) ＞ 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 spliting with decay variables:

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

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(D 0 +D *0 )=3871.5±0.5MeV (coincident?) appears unexpectedly narrow

Summary of X(3872): - (522±100) candidates of signal are established with 230 pb -1 data - Selected production/decay properties of X(3872) are similar to those of  (2S) within error - Confirm the existence of X(3872) with mass difference △ M = M(X) – M(J/  ) = ± 3.1(stat) ± 3.0(syst) MeV/c 2  search for charged analog, X +  J/  +  0  search for radiative decays - Next step:

The observation of Bc  J/  (  +  - )  + 

Bc -- last of ground state of meson - The only previous evidence by CDF RunI - Theory predictions : [1] C.Chang et al, PRD49(1994)3399 [2] E.Ebert et al, hep-ph/ ; PRD68(2003) M Bc ~ 6.4 GeV  Bc ~ ps -- c  ~100  m, significantly shorter than B Bc ±  J/  (  +  - )  ± -- Br~2.4% + trilepton final state + easy to trigger

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

Signal shape (MC): - MC templates of M Bc 5.5 – 6.7 with 0.1GeV interval - Full detector smearing + Selection Background shape (data): - use J/  +1 track control data sample - divided into 2 subsets: 1) “prompt” J/  2) “heavy flavor” one from B decay - cross-checked with  (2S) + 1 track bkg dominated data Bc Fit: extract signal from a combined unbinned likelihood fit to J/  invariant mass and proper time 5.95 ±0.34 GeV Bc mass log likelihood

“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

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

Systematic uncertainties:

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

Summary: Preliminary results on Bc with significantly more statistics Events: 95 ± 12±11 Mass: 5.95 ±0.34 GeV/c Lifetime: ±0.121 ps

The production of Upsilon(1S)

Theory modeling of production: - factorized QCD calculations to O(  3 ) currently employed by Pythia - color-singlet, color-evaporation, color-octet models  (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

 ’s |y|   ‘s P T  Data sample partition: -  y1: 0 ＜ |y  | ＜  y2: 0.6 ＜ |y  | ＜  y3: 1.2 ＜ |y  | ＜ 1.8 Sample fit: - Background: 3 rd order polynomial -  (1,2,3S) resonances: double Gaussian - the mass and width of  (1S) are free parameters; others are fixed relative to the mass

Evaluating the  (1S) Production Xsec: with eff in different rapidity region: The measured cross-section × BR(  (1S)   ) 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

Summary: measurements of  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, d  /dy*Br =680±15±18±26 pb - D0 √s=1.96TeV, |y|<0.6, d  /dy*Br =749±20±75±49 pb - PYTHIA predict a factor of 1.11 from 1.8 to 1.96 TeV

Thank you!

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