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Heavy Flavour Physics News from the Tevatron

Heavy Flavour Physics News from the Tevatron

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Heavy Flavour Physics News from the Tevatron

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  1. Heavy FlavourPhysicsNews from the Tevatron Wendy Taylor for the CDF and DØ Collaborations APS/AAPT 2010, Washington, DC, February 13-16, 2010

  2. The b Quark as a Physics Probe Primary vertex • Where is the antimatter in the Universe? • Why are there 3 generations of matter? (only 3?) • How does the strong force bind quarks into hadrons? • How does the electroweak force cause hadrons to decay? B decay vertex Displaced track W. Taylor, APS/AAPT 2010

  3. The Tevatron is a B Factory • Why study B physics at the Tevatron? • Large rate: • Tevatron energy sufficient to create states not accessible at the e+e- B factories • However, backgrounds are large: W. Taylor, APS/AAPT 2010

  4. Run II Tevatron Proton-Antiproton Collider s=1.96 TeV L =2.51032cm-2s-1 Ldt=50 pb-1 per week Chicago  Booster CDF DØ Tevatron p source Main Injector Fermi National Accelerator Laboratory W. Taylor, APS/AAPT 2010

  5. Detectors • Excellent muon and tracking coverage  high yields • Extended muon system ||<2.0 • Tracking up to ||<3.0 • Solenoid and muontoroid polarities flipped every two weeks • Excellent mass resolution • Particle ID: p, K and  by dE/dx and TOF • L1 trigger on displaced two-track objects W. Taylor, APS/AAPT 2010

  6. B(u,d,s)→+-h FCNC Decays • Flavour-changing neutral current decays are highly suppressed in the SM as they do not occur at tree-level (i.e., lowest order) • New physics (e.g., SUSY, technicolour, 4th generation*) might occur in internal loops • Could enhance the branching fractions significantly • Could also affect the angular distributions * W.-S. Hou et al., PRD 76 016004 (2007) W. Taylor, APS/AAPT 2010

  7. B(u,d,s)→+-h Decays • Trigger on two muons in 4.4 fb-1 • Final offline selection uses neural network • Use unbinned maximum log-likelihood fit to invariant mass • CDFnote 10047 6.3 9.7 8.5 W. Taylor, APS/AAPT 2010

  8. B(u,d,s)→+-h Decays • SM predicts Br ~ O(10-6) • Use as normalization channel for branching fraction to avoid many systematic uncertainties • Precision competitive to world average values: • First ever measurement: • The rarest measured Bs0 decay! • Theoretical prediction of 1.6110-6(Geng and Liu, J.Phys.G29:1103-1118,2003) agrees well W. Taylor, APS/AAPT 2010

  9. B0→K*0+- Decays • K*0 forward-backward asymmetry AFB • µ is helicity angle between µ+ direction and the opposite of the B direction in the dimuon rest frame • K*0 longitudinal polarization FL from angle K between the kaon and the B direction in the K*0 rest frame • Divide data into 6 bins of q2=m2(µ+µ-)c2 W. Taylor, APS/AAPT 2010

  10. B0→K*0+- Decays • Precision is competitive with B factory measurements • Experimental results are consistent Babar Belle SM SM PRL 103, 171801 (2009) PRD 79, 031102(R) (2009) SM lower than data by 2.7 W. Taylor, APS/AAPT 2010

  11. B(d,s)→+- Rare Decays • SM expected limits: • Br(Bd→+-)<(1.00±0.14)x10-10 ~|Vtd|2 • Br(Bs→+-)<(3.86±0.57)x10-9 ~|Vts|2 • New physics could introduce tree-level contributions • can enhance the branching fraction by x100 over the SM prediction W. Taylor, APS/AAPT 2010

  12. B(d,s)→+- Rare Decays • Utilize muons with ||<2.0, pT>2.0 GeV/c • Boosted decision tree • B-candidate decay length significance • B-candidate pT • B-candidate track isolation • Impact parameter significance • Vertex 2 probability • Assume no contribution from Bd→+- (|Vtd/Vts|2~0.04) • DØnote 5906 W. Taylor, APS/AAPT 2010

  13. B(d,s)→+- Rare Decays • Utilize muons with ||<1.0, pT>2.0 GeV/c • Muons form B-candidate vertex • Neural-net variables • B-candidate decay length and significance • B-candidate track isolation • Opening angle between B- candidate momentum and decay length • pT(B) and pT(µLow) • CDFnote 9892 W. Taylor, APS/AAPT 2010

  14. B(d,s)→+- Rare Decays • At 95% CL in 3.7fb-1:Br(Bd→+-)<7.6x10-9 Br(Bs→+-)<4.3x10-8 • Expected upper limitin 5fb-1 : Br(Bs→+)<5.3x10-8 (95% CL) W. Taylor, APS/AAPT 2010

  15. B(d,s)→+- Rare Decays • Enhancements over SM greater than ~10x already excluded • Combined Tevatron expected limits may reach 4x with 8fb-1 • Stay tuned! NP? W. Taylor, APS/AAPT 2010

  16. Upsilon Polarization • Non-Relativistic Quantum Chromodynamics (NRQCD) • QQ production is perturbative short-distance process • Hadronization into  is long-distance process, which is expanded in powers of heavy quark velocities • Past CDF measurements of J/ and (2s) polarization do not agree with NRQCD • Reconstruct (1s)→+- decays • In the  rest frame, + makes an angle * with respect to the  direction in the lab frame •  = 1 for fully longitudinal polarization •  = +1 for fully transverse polarization W. Taylor, APS/AAPT 2010

  17. Upsilon Polarization • Apply simulated trigger conditions and offline cuts • Get templates reflecting how fully polarized events would appear in the detector • Dimuontrigger: pT(1)>4GeV/c, pT(2)>3GeV/c, <0.6; Offline: require good dimuon vertex, with mass consistent with (1s) • Generate MC samples with fully transverse and fully longitudinal polarizations W. Taylor, APS/AAPT 2010

  18. Upsilon Polarization • Determine polarization parameter by matching a polarization-weighted combination of templates to the *(+) distributions in the data in each of eight pT() bins • Apparent disagreement with NRQCD and DØ result • Look forward to new DØ J/ and  polarization results W. Taylor, APS/AAPT 2010

  19. CP Violation • Violation of the Charge-Parity Symmetry • Charge symmetry: matter  antimatter • Parity symmetry: like a mirror symmetry but in 3D W. Taylor, APS/AAPT 2010

  20. CP Violation • Violation of the Charge-Parity Symmetry • Charge symmetry: matter  antimatter • Parity symmetry: like a mirror symmetry but in 3D • Large sources of CP violation would explain the observed matter-antimatter asymmetry of the universe W. Taylor, APS/AAPT 2010

  21. CP Violation in Bs0 Mixing Antimatter Matter • Bs0 mixing: • If , an excess of Bs0 would “build up”  CP violation • Search for a charge asymmetry in decays versus decays W. Taylor, APS/AAPT 2010

  22. CP Asymmetry in Bs0Semileptonic Decays • Need to correct for detector asymmetries • Muontoroid polarity flip • Use decay time information • Tagging mixed versus unmixed decays helps arXiv:0904.3907 W. Taylor, APS/AAPT 2010

  23. CP Phase sin Bs0J/ Decays • Get two mass eigenstates: • SM predicts • New physics (e.g., 4th generation) could contribute a large phase sNP • Use Bs0J/ decays: golden mode • yield both CP-even and CP-odd final states, which have different angular distributions • Can separate the CP components via a time-dependent angular analysis of decay products W. Taylor, APS/AAPT 2010

  24. CP Phase s in Bs0J/ Decays DØnote 5928 2.12 For large sNP: CDFnote 9787 W. Taylor, APS/AAPT 2010

  25. CP Phase s with ASL Constraint Assl=ΔΓs/Δmstan(s) W. Taylor, APS/AAPT 2010

  26. b Baryons • B spectroscopy measurements provide sensitive tests of potential models, heavy quark effective theory (HQET), and lattice gauge theory b- b- W. Taylor, APS/AAPT 2010

  27. Resonant Structure in b0c+-+- • Reconstruct 84893 b0c+-+- events where c+pK-+ in 2.4 fb-1 • Observe resonant structures: • b0c(2595)+-c+-+- • b0c(2625)+-c+-+- • b0c(2455)++--c+-+- • b0c(2455)0+-c+-+- • Measure branching fractions relative to b0c+-+- • Comparetheoretical predictions to measured branching fractions to test heavy quark effective theory (HQET) • Important for measurement of Br(b0c+-) W. Taylor, APS/AAPT 2010

  28. Resonant Structure in b0c+-+- • Sample collected by the impact-parameter trigger • Look for resonances with respect to M(c+) • Veto c* resonances for c* search W. Taylor, APS/AAPT 2010

  29. Resonant Structure in b0c+-+- W. Taylor, APS/AAPT 2010

  30. b- (ssb) Baryon Observation • Use J/µ+µ- sample • Need to reconstruct three decay vertices • DØ uses BDT selection, unbinned likelihood mass fit and b-J/ - decays for many cross-checks • CDF uses a cut-based selection with B0J/K*0 and B0J/Ks0 decays for cross-checks W. Taylor, APS/AAPT 2010

  31. b- (ssb) Baryon Observation 4.2fb-1 M(b-)=6054.46.8(stat)0.9(syst) MeV/c2 PRD 80, 072003 (2009) M(b-)=616510(stat)13(syst) MeV/c2 PRL 101, 232002 (2008) S. Godfrey, DPF 2009 Proceedings M=|MD0-MCDF|~6 W. Taylor, APS/AAPT 2010

  32. b- (ssb) Baryon Observation • CDF and DØ measurements of the b- mass agree • DØ:M(b- )=577411(stat)15(syst) MeV/c2 (PRL 99, 052001 (2007)) • CDF: M(b- )=5790.92.6(stat)0.9(syst) MeV/c2 • DØ is performing new analysis with 5 x data • Half the new sample includes the new Layer 0 silicon detector • CDF could at best double its dataset, but could also include additional channels • Stay tuned! W. Taylor, APS/AAPT 2010

  33. Conclusions • The Tevatron experiments are very active in B physics and things are getting interesting! • CDF/DØ  polarization • CDF/DØ b- mass • CP violation in Bs0J/ • Bs0→+- • Tevatron is funded to run through 2011  10fb-1 • Need to improve analysis techniques too • Can expect many improved results and maybe new discoveries in the next two years! W. Taylor, APS/AAPT 2010