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Alberto Sánchez Hernández CINVESTAV (Mexico City) DØ Collaboration

Heavy Flavor Physics at DØ. Alberto Sánchez Hernández CINVESTAV (Mexico City) DØ Collaboration. DØ Detector. Tracker. SMT+ CFT  max = 1.65. 8 ×2 CFT layers. SMT region  max = 2.5.  = - ln (tan(/2)). 4 SMT layers. Trigger: muon+track covers |  |<2.2. Tracking Performance.

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Alberto Sánchez Hernández CINVESTAV (Mexico City) DØ Collaboration

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  1. Heavy Flavor Physics at DØ Alberto Sánchez Hernández CINVESTAV (Mexico City) DØ Collaboration

  2. DØ Detector

  3. Tracker SMT+ CFT max = 1.65 8×2 CFT layers SMT region max = 2.5  = - ln (tan(/2)) 4 SMT layers Trigger: muon+track covers ||<2.2

  4. Tracking Performance Impact Parameter Resolution SMT dE/dx MC  Data Can provide K/ separation for Ptot<400 MeV p/ separation for Ptot<700 MeV NOT yet used for PID (DCA)53m @ Pt=1GeV and 15 m @ higher Pt

  5. Tracking Performance Data from semileptonic decays (B  m D X) || for kaons from D*D0 pT spectrum of soft pion from D*D0 • Tracks are reconstructed • over a wide  range • starting from pT = 180 MeV Efficient muon and tracking system give us a large sample of semileptonic B decays

  6. A New Particle: X(3872) • Last Summer BELLE announced a NEW particle around 3872 MeV/c2 when looking at B  K+X (X  J/ p+p-) • possible charmonium state or an exotic meson molecule (?) • BELLE didn’t find evidence for c1 CDF II: hep-ex/0312021 BELLE: PRL91,262001,(2003) • X(3872)  J/ p+p- production in ppbar collisions has been confirmed by CDF

  7. What can we say about the X(3872)? • Using 200 pb-1 of DATA collected April 2002 – September 2003, we look for X(3872)  J/ p+p- • SMT 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

  8. Properties of X(3872) • Look if production characteristics are similar to (2S). • Data was binned for different variables: decay- length, isolation, h (pseudo- rapidity) pT, and helicity of (+ -)

  9. X(3872) - (2S) comparison Yield given cut / Total Yield Within the current statistical uncertainties, the production of X(3872) has similar behavior as the cc(bar) state (2S)

  10. What is X(3872)? • If the charged analog X+J/p+p0was observed,then cc(bar) hypothesis could be ruled out • While observing radiative decays Xc1 would favor cc(bar) hypothesis • Both of these would require DØ to identify low energy p0 and  (work in progress) • Our tests show: production characteristics of X(3872) (in the used variables) seems similar to those from (2S) (within the statistical uncertainties), this would tend to favor a cc(bar) hypothesis, but we do not know (yet) how these characteristics look for an exotic meson-molecule (theoretical input needed).

  11. B Semileptonic Samples • Muon: • Pt > 2 GeV/c • nSMT > 1 • nCFT > 1 For Mixing and Lifetime studies • Charged tracks: • pT > 0.7-1 GeV/c • Secondary Vertex • Lxy / L > 4 • cos((L,PD))>0.95

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

  13. (Bd)/(Bs) =1±0.01 (0b)(b) < (Bd) < (-b) < (b) (b)-(-b) 0.11±0.03 ps-1 0.9 < (b)/(Bd) <1 Comparisons B Lifetime Measurements Report of the B Physics at the Tevatron Workshop (12/2001) Predictions Experimental Results • (B) = 1.573±0.008 ps • (B0) = 1.534±0.013 ps • (B+) = 1.652±0.014 ps • (B+)/(B0) = 1.081±0.015 • (BS) = 1.439±0.053 ps • (bbaryon) = 1.210±0.051 ps • (b) = 1.233+0.078 ps -0.076 B Lifetime Group (Summer 2003)

  14. 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 ’ 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

  15. B Lifetime from Inclusive BJ/+X b J/ X £dt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

  16. B± Lifetime from B±J/K± £dt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)

  17. Bd,s Lifetimes from BJ/+K0*, Similar kinematicsSome systematic errors can be cancelled in ratio! £dt114 pb-1 Signal: 105±19 Signal: 69±13 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

  18. 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 We will use this for mixing studies

  19. Mixing: Flavour tagging • Use flavour-specific decays to get flavour of B at decay. To get flavour of B at production use • - Soft-lepton tags- High dilution power, low efficiency (SL decay of other B) • - Jet Charge tag- Poorer dilution power, high efficiency (track-jet from other b quark) • - Same Side tagging- Poorer dilution power, high efficiency (fragmentation, B**) • We test this tools using B+ data sample

  20. Opposite Side Muon Tagging • PT > 1.9 GeV • Q – charge of muon with the highest PT • Classification: • Q!= QK : correct tag • Q== QK : wrong tag • No muon : No tag B±J/K± DØ RunII preliminary • D = (57.0 ± 19.3)% •  = ( 5.0 ± 0.7)% • D2 = (1.6 ± 1.1)% 

  21. Q = Ptq/Pt • D = (26.7 ± 6.8)% •  = (46.7 ± 2.7)% • D2 = (3.3 ± 1.7)% DØ RunII preliminary Opposite Side Jet Charge Tagging B±J/K± • PT > 0.5 GeV • ZPV < 2 cm • Classifications: • |Q|>0.2 && sign(Q) != QK : correct tag • |Q|>0.2 && sign(Q) == QK : wrong tag • |Q|<0.2 : no tag

  22. Same Side Tagging Excited B** decays into B and pion/kaon that carries the initial state flavor information Example: B**d B+- +±

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

  24. Search for Bs m+m- MC Ldt100 pb-1 Br(Bs m+m- ) < 1.6  10-6 at 90% CL

  25. Summary • DØ has observed the X(3872) particle in 200 pb-1 data • Statistical significance of 4.4s • M = 0.7684  0.0035 (stat)  0.0039 (sys) • Data separated into various regions, we found similar behaviour as (2S), within statistical uncertainties • Many other results as B physics program under way • We have reprocessed  200 pb-1 of data to better improve our analyses • A lot more interesting results very soon!

  26. More Data Reprocessed Ldt200 pb-1 Ldt 114 pb-1

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