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B 0 s  J/ y f LHC review

B 0 s  J/ y f LHC review. Nicolò Magini University and INFN, Firenze For the ATLAS, CMS and LHCb collaborations Oxford, 28 th September 2006 Beauty 2006 The 11 th International Conference on B-Physics at Hadron Machines. Outline. B 0 s mesons and the B 0 s  J/ y f decay

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B 0 s  J/ y f LHC review

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  1. B0s  J/yfLHC review Nicolò Magini University and INFN, Firenze For the ATLAS, CMS and LHCb collaborations Oxford, 28th September 2006 Beauty 2006The 11th International Conference on B-Physics at Hadron Machines

  2. Outline • B0s mesons and the B0s  J/yf decay • Reconstruction and selection with LHC detectors • Analysis and parameter extraction B0s J/y fLHC review

  3. B0s mixing s B0s B0s s s Bs are too heavy to be produced at U(4s) B factories • studied with high statistics at hadron colliders • CDF and D0 results on mixing • Standard Model prediction for DGs/Gs ~ 0.10 • DGs= 0.54 DGs= 0.54 17 ps-1 <Dms <21 ps-1 @ 90% CL Dms =17.77 ± 0.10 ± 0.07ps-1 B0s J/y fLHC review

  4. Bs  J/   m+m-K+K- BR(BsJ/ )=(9.3±3.3)x10-4 BR(J/m+m-)=(5.93±0.06)% BR (K+K-)=(49.2±0.6)% Vts* Vtb Vcb s t V*cs b t s Vtb Vts* CP violating weak phase SM predicts s = 2bs~ O(0.03) B0s J/y fLHC review

  5. New physics in s • Present measurements still allow for almost arbitrary NP contributions to s • Measuring s will greatly constrain flavour violation in NP models B0s J/y fLHC review

  6. Bs J/  ℓ+ K+ ℓ- K- p p Bs decay products are both JPC = 1--states The final state hasCP = +1ifL = 0,2andCP = -1ifL = 1 The two contributions with opposite CP can be separated with an angular analysis of the final decay products B0s J/y fLHC review

  7. Angular distributions Time evolution is a function of the transversity amplitudesA0(t), A||(t) (CP = +1)and A(t) (CP = -1) Known functions of the three angles ,y,fdescribing decay product kinematics in the transversity basis B0s J/y fLHC review

  8. Angular distributions - tagged moduli2 interference The distributions depend on 8 independent parameters • Amplitudes |A||(0)|,|A(0)| - Strong phases 1, 2 • Width difference ΔΓs = (ΓH - ΓL) - Average width Γs = (ΓH+ΓL)/2 • Mass difference Δms- Weak phase s B0s J/y fLHC review

  9. Angular distributions - untagged • Remarkable feature: • If DGs≠0 the distributions are still sensitive to the weak phase fs • Terms with Dms cancel: not necessary to resolve the very fast oscillations B0s J/y fLHC review

  10. b production atLHC Luminosity 2x1033 cm-2s-1 (ATLAS, CMS 2009) 2x1032 cm-2s-1 (LHCb) s = 0.5 mb  about 106 (105) bb pairs/sec B Physics at LHC B0s J/y fLHC review

  11. The detectors CMS ATLAS LHCb • Dedicated forward detector • RICH for PID • Triggering VELO • Multipurpouse central detectors B0s J/y fLHC review

  12. Trigger selection Details in talks by J. Kirk and E. Rodrigues ATLAS/CMS LHCb • Di-muon trigger at L1 • Decay chain reconstruction with fast/regional tracking at HLT (lifetime biased) • Di-muon trigger at L0 • L1/HLT: lifetime unbiased single & di-muon streams + lifetime biased J/y stream ATLAS : pT (m,m) > 6,3 GeV/c CMS : pT (m,m) > 3,3 GeV/c LHCb : SpT(m1,m2) > 1.5 GeV/c B0s J/y fLHC review

  13. Offline reconstruction K+ K- s • m reco with tracker + ID with muon detector • K reco with tracker - ID only in LHCb • Common 4-track vertex • p(B0s) // L • Flavour tagging B0s J/y fLHC review

  14. Kinematic fitting Constraints applied • Common 4 track vertex • J/y mass constraint • Vertex pointing constraint CMS Mass resolution = 14 MeV/c2 B0s J/y fLHC review

  15. Proper time resolutions CMS - st = 77 fs LHCb - <terr> = 36.0 fs ATLAS - st = 84 fs B0s J/y fLHC review

  16. Event yields Background is mostly combinatorial for LHCb, combinatorial + B0J/yK*0m+m-K±p+ for ATLAS/CMS ( ) ( ) B0s J/y fLHC review

  17. Angular analysis • Goal: extract from the angular distributions of the decay products the parameters of interest (e.g. DGs/Gs , fs) • In principle: single maximum likelihood fit to extract the parameters simultaneously from all available data • In practice: many parameters, complicated distributions  use different multi-step approaches to fitting B0s J/y fLHC review

  18. First step: untagged fit • Example: CMS measurement of DGs/Gs , fs Maximum likelihood fit with P.D.F. signal BdJ/yK* bkg Combinatorial bkg Angular distributions to extract e(t,Q) – selection efficiency as function of proper time & angles Gs(m,ms,ss) – mass resoultion (gaussian) B0s J/y fLHC review

  19. Selection efficiency • e(t,Q) • As a function of proper time • As a function of angles B0s J/y fLHC review

  20. Results – untagged analysis • Statistical error for 100k evts (NSEL with Lint = 10 fb-1) CMS also evaluated Angular Moments analysis, results only slightly worse than MLH fit • Systematical errors for 13k evts (NSEL with Lint = 1.3 fb-1) Main source is modeling of proper time bias  need control samples to measure in data B0s J/y fLHC review

  21. Next step: tagged fit • Example: LHCb one-angle distribution analysis • Flavour tagging methods used: • OS l, OS K, OS Vtx charge, SS K • Performance e=57%, wtag=33%  eeff=6.6% • Dms and wtag determined using BsDsp as control sample B0s J/y fLHC review

  22. Results: tagged analysis • LHCb also combines other lower statistics decays to CP eigenstates (no angular analysis) • Could also add J/y e+e- channel (not included here, statistics 1/6 of J/y m+m-) B0s J/y fLHC review

  23. Results - summary Results for one year at nominal low luminosity B0s J/y fLHC review

  24. Conclusions • Any large NP effect will be seen “soon” • SM value of fs will be found at 3s within 5 years data taking at LHCb • ATLAS & CMS can also give good contributions to the measurement B0s J/y fLHC review

  25. Acknowledgements • M. Smizanska, J. Catmore for the ATLAS collaboration • V. Ciulli, N. Magini, L. Wilke, T. Speer, K. Prokofiev, S. Shulga, T. Ilicheva for the CMS collaboration • J. Van Hunen, L. Fernandez for the LHCb collaboration B0s J/y fLHC review

  26. References • CMS-NOTE 2006/121 • LHCb NOTE 2006/047 and L. Fernandez, PhD Thesis • ATLAS Physics and detector performance TDR. Vol. II B0s J/y fLHC review

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