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Recent B Physics Results: Observation of X(3872) and B Meson Lifetimes at DØ

On February 18, 2004, Bill Lee from Florida State University presented new B physics results from the DØ experiment. Highlighting significant findings, the search for the X(3872) revealed approximately 300 candidate events, showing production characteristics resembling those of the ψ(2S) meson. Additionally, B meson lifetimes were measured, yielding results that conform closely with Particle Data Group values. The presentation emphasized ongoing efforts in flavor tagging and Bs mixing studies, leveraging large datasets collected during Run II at the Tevatron, with expectations for more discoveries soon.

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Recent B Physics Results: Observation of X(3872) and B Meson Lifetimes at DØ

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  1. Recent B Physics Results at DØ Bill Lee Florida State University 18 February 2004 • X(3872) • B Lifetime and Mixing • Bs m+m- Search

  2. The DØ Run 2 Detector SMT

  3. X(3872) at D0 • Using 200 pb-1 of DATA collected April 2002 – September 2003, we look for X(3872)  J/ p+p- • Silicon hit > 1 • num tracks < 100 • pT(J/) > 4 GeV/c • 2.8 < M(m+m-) < 3.4 GeV/c2 • pT() > 0.4 GeV/c • ’s within same cone as J/ • M(+ -) > 0.52 GeV/c2 • M(m+m- + -) -M(m+m-) < 1.0 GeV/c2 • 2 (m+m- + - - vertex) < 16 • |zvertex| < 35 cm 4.4s effect 300  61 X(3872) candidates DM = 0.7684  0.0035 (stat)  0.0039 (sys) GeV/ c2

  4. Properties of X(3872) • Are the production characteristics similar to the (2S)? • To compare, the data was binned for several different variables: decay-length, isolation, h (pseudo-rapidity), pT, and helicity of (+ -)

  5. X(3872) and (2S) comparison Yield per given cut / Total Yield Within the current statistical uncertainties, the production of X(3872) has similar behavior as the (2S), but an exotic meson could also behave similarly.

  6. Is X(3872) charmonia? • If the charged analog X+J/p+p0was observed,then cc hypothesis could be ruled out • While observing radiative decays Xc1 would favor cc hypothesis • Both of these would require DØ to identify low energy p0 and  (work in progress) - -

  7. 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 (2s) Signal = 8.22K events Mass = 3.668 ± 0.002 GeV/c2  = 0.071 ± 0.002 GeV/c2 J/ Signal = 290.3k events Mass = 3.0718±0.0002 GeV/c2  = 0.0741±0.0002 GeV/c2

  8. B Lifetime from Inclusive BJ/+X B J/ X Ldt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 B’s = 18%  = 1.562  0.013  0.045 ps Correction factor leads to the major systematic error

  9. Bd,s Masses (J/ + K0*,,K0s) For CP and Lifetime studies

  10. B± Lifetime from B±J/K± Ldt114 pb-1 Fully reconstructedNo Correction Factor! <B±>=1.65±0.083(stat)±0.123(syst) ps <B±>=1.671±0.018 ps (PDG)

  11. Bd,s Lifetimes from BJ/+K0*, Similar kinematicsSome systematic errors can be cancelled in ratio! Signal: 105±19 Signal: 69±13 Ldt114 pb-1 Bd=1.51+0.19(stat) ± 0.20(syst) ps -0.17 PDG: Bd = 1.537 ± 0.015 ps Bs=1.19+0.19(stat) ± 0.14(syst) ps -0.16 PDG: Bs = 1.461 ± 0.057 ps Bs/Bd=0.79 ± 0.14 PDG: Bs/Bd = 0.95 ± 0.038

  12. Large B Semileptonic Sample • Muon: • Pt > 2 GeV/c • Charged tracks: • pT > 0.7-1 GeV/c • Secondary Vertex • Lxy / L > 4 • cos((L,PD))>0.95

  13. 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 B=1.564 ± 0.014 ps (PDG) We will use this for mixing studies

  14. Mixing: Flavor tagging • In order to study Bs mixing we will need • final state reconstruction • ability to measure B decay lengths • the ability to tag the flavor of the B at production and decay. • We can use flavor-specific decays to get the flavor of the B at decay. To get the flavor of the B at production we use three methods: - Soft-lepton tags - Jet Charge tag - Same Side tagging • We can test these tools using our B+ data sample

  15. Flavour Tagging results DØ RunII Preliminary Muon DATA, we will also use electrons Performance with B0/Bs is under study

  16. Search for Bs m+m- SM: Br(Bs m+m- ) = 3.7 10-9 Some SUSY tan(b) models can enhance the signal. MC Dimuon spectrum Ldt100 pb-1 No Excess Seen. Br(Bs m+m- ) < 1.6  10-6 at 90% CL

  17. Summary • DØ has observed the X(3872) particle in 200 pb-1 data • We have reprocessed  200 pb-1 of data to better improve our analyses. • D0 will be able to study Bs mixing • Tevatron is performing well. • D0 recorded 9.4 pb-1 last week. • Lots of data. • Many more interesting results coming very soon!

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