1. CP Violation Recent results and perspectives João R. T. de Mello Neto Instituto de Física Universidade Federal do Rio de Janeiro 22-26 July,2003

2. Outline Introduction CP Violation in the SM Measurement of β B Factories results Other measurements Dedicaded hadron colliders experiments –LHCb, BTeV Conclusion

3. Motivations SM with 3 generations and the CKM ansatz can accomodate CP CP is one of the less experimentally constrained parts of SM Observations of CP in the B system can: test the consistency of SM lead to the discovery of new physics Cosmology needs additional sources of CP violation other than what is provided by the SM. CP violation is one of the fundamental phenomena in particle physics CP asymmetries in the B system are expected to be large.

4. I will not talk about: Kaon physics Strong CP problem; CP violation in the charm sector; CP violation in Cosmology! Concentrate in CP violation in the B sector (Only a small subset!)

5. CLEO 3 BELLE 1999 2001 BTEV ATLASATLAS ? 1999 2008 Huge experimental effort Plus hundreds of experimental groups around the World.

6. Matter – antimatter oscillations decay ordinary ΔB=1 interactions exchange of virtual q (2/3) t : dominant amplitude ΔB=2 V td ΔmdΔmd f B decay constant B B Bag factor Neutral B 0 mesons oscillate b d d b t t w-w- w-w- c e-e- b d w-w- d

7. CKM matrix = = mixing phase Weak decay phase mixing phase The quark electroweak eigenstates are connected to the mass eigenstates by the CKM matrix : four parameters A, λ, ρ, η

8. Unitarity triangles V td V tb  +V cd V cb  +V ud V ub  = 0 (0,0)     V ub   V cb  V td (,)(,) (1,0) V td V ud  +V ts V us  +V tb V ub  = 0  V ub   V td  V ts   In SM: measure all the angles measure all the sides SM: consistency!

9. CP violation Three possible manifestations of CP violation: Direct CP violation (interference between two decay amplitudes) Indirect CP violation (interference between two mixing amplitudes) CP violation in the interference between mixed and unmixed decays

10. time-dependent formalism for B d decay amplitude for time evolution CP violation: interference between mixing and decay

11. time-dependent formalism for B d B-factories: Δt LHCb, BTeV: t C=0 B 0 →J/ψK S S=+sin(2β) SM: C=0 S=-sin(2β) B 0 →J/ψK L

12. Measuring β Decays such as B 0 →J/ψK S and B 0 →J/ψK L theoretically well understood: tree and leading penguin have same phase “relatively simple” experiment

13. Measuring β (from D. Lange)

14. B factories: Belle, BaBar Assimetric colliders at One year: ~ 100 M pairs Belle 132 fb -1 March, 2003 BaBar 117 fb -1 Coherent production

15. KEKB Luminosity achieved: 1.06 x 10 34 cm -2 s -1

16. Babar detector

17. Mixing and lifetimes large samples of ohadronic decays: fully or partially reconst. osemileptonic decays (D * l  fully or partially reconst. odileptons 8K events 12K events 29 fb -1

18. Δt distributions and lifetimes Δt = proper time difference between the decay times of the two B-mesons Δt resolution of ~ same order of magnitude as lifetime  0 = 1.554  0.030  0.019 psec  - = 1.695  0.026  0.015 psec proof of principle: resolution function under control.

19. Lifetimes results summary Belle and BaBar now dominate world averages Improvement by x2 over pre B-factory era Order 1% uncertainty on lifetimes and ratio

20. Adding Tagging Information  m d = 0.516  0.016  0.010 ps -1 (30 fb -1 ) A mix (t)

21. Event samples ~500 K L signal events 60% purity ~1600 K S events

22. Δ t distributions and asymmetries CP=-1 CP=+1 B0→J/ψK S B0→J/ψK L

23. Δt distributions and asymmetries

24. Summary of sin2b in b  ccs already a precise measurement: 7.5%

25. rarer B decays Cabbibo supressed B 0 → J/   0 B →  K S B →  ‘ K S  Sensitive to new physics: smaller amplitudes, NP through interf. terms virtual particles (SUSY?) in penguin loops not theoretically clean smaller rates, higher back. Same CKM structure as B 0 →J/ψK S expect S=sin2β to 5%

26. B 0 → J/   0 S = - sin2β if no penguin C = 0 if no penguin

27. Measuring β in b → sss

28. Theoretical especulations sin(2β) = S ϕK =-0.39 +- 0.41 (2.7 σ) from the SM prediction; models from SUSY could explain this result! G.L. Kane et al., PRL Apr.2003 Grossman et al. hep-ph/0303171

29. SM is alive and well! Confidence levels in the large (rhobar,etabar) plane obtained from the global fit. The constraint from the WA sin2beta (from psi Ks modes) is overlaid. Confidence levels in the large (rhobar,etabar) plane obtained from the global fit. The constraint from the WA sin2beta (from psi Ks modes) is included in the fit.

30. 2007 More data close to theory limit from penguin pollution; Measurement of Δm S improve |V td /V cb | from near cancellation of B d and B s form factor; More data from B→h u lν and B→h c X together with improvement in theory will give some improvement in |V td /V cb | ;

31. Strategy: new physics! now 2007 1 yr LHCb B d  J/  K S B d  B s  J/  Bs DsKBs DsK statistics!! Goal: Physics beyond the Standard model Measurements which provide a reference case for SM effects; Compare this to channels that might be affected by New Physics; Understand experimental and theoretical systematics to a level where we can draw conclusions.

32. for larger the B boost increses rapidly Hadronic b production B hadrons at Tevatron b quark pair produced preferentially at low  highly correlated tagging low pt cuts

33. LHCb Experiment Acceptance : –15-300mrad (bending) –15-250mrad (non-bending) Particle ID –RICH detectors –Calorimeters –Muon Detectors Dedicated B physics Experiment at the LHC –pp collisions at 14TeV RICH1 Z ~ 1.0-2.2 m RICH2 Z ~ 9.5-11.9 m Calorimeters Z ~ 12.5-15.0 m Muon System Z ~ 15.0-20.0 m

34. One event!

35. for the decay channel B s  D s  + D s  KKπ Tracking performance Average efficiency = 92 % Efficiency for p>5GeV >95% Ghost rate p T >0.5 GeV ~ 7%. Mass resolution (~13 MeV) (~13 MeV) Momentum resolution:  p/p=0.38% Proper time resolution (42 fs) resolution (42 fs) = 27 tracks/event = 27 tracks/event

36. Hadron ID : Physics Performance No RICH With RICH n Signal Purity improved from 13% to 84% with RICH n Signal Efficiency 79% n RICH essential for hadronic decays n Example : B s  K + K - n Sensitive to CKM angle 

37. Muon Identification Muons selected by searching for muon stations hits compatible with reconstructed track extrapolations –Compare track slopes and distance of muon station hits from track extrapolation For P>3GeV/c  eff = 96.7  0.2 %  misid = 2.50  0.04 %

38. BTeV detector

39. Calorimetry Important final states with and Use 2x11,850 lead-tungsten crystals (PbWO 4 ) technology developed for LHC by CMS radiation hard fast scintillation (99% of light in <100 ns) Excellent energy, angular resolution and photon efficiency

40. Strategies for measurements of CKM angles and rare decays Rare

41. Measuring β  “gold-plated” decay channel at B-factories for measuring the B d - B d mixing phase  needed for extracting γ from B d  ππ and B s  K K  in SM A dir =0, non-vanishing value (~0.01) could be a signal of Physics Beyond SM  precision measurement important Inputs: 220 k/year signal 194 k/year back. A mix =sin(2β)=0.73 A dir = 0 ps A CP (t)

42. Systematic errors in CP measurements high statistical precision asymmetries ratios robust production asymmetries tagging efficiencies mistag rate final state acceptance Control channels Monte Carlo Detector cross-checks CP eigenstates

43. from B s  J/ψϕ  “ gold-plated” decay channel for hadron machines, measuring the B s - B s phase  in SM expected to be ~0.03  large CP asymmetry would signal Physics Beyond SM  also needed for extracting from B s →ππ and B s  K K, or from B s  D s K  J/ψϕ is not a pure CP eigenstate  2 CP even, 1 CP odd amplitudes contributing  need to fit angular distributions of decay final states as function of proper time  requires very good proper time resolution with input values: ε tag = 30%, ω tag = 30%, Δm s =20/ps = 1.5 ps,, A = sin(-  ) = 0.03 σ t = 38 fs in 1 year:  σ  

44. Measuring  Using B o         A Dalitz Plot analysis gives both sin(2  ) and cos(2  ) (Snyder & Quinn) Measured branching ratios are: –B(B       = ~10 -5 –B(B      +      = ~3x10 -5 –B(B       <0.5x10 -5 Snyder & Quinn showed that 1000- 2000 tagged events are sufficient Not easy to measure –  0 reconstruction Not easy to analyze –9 parameter likelihood fit

45. Measuring  Using B o         Based 9.9x10 6 background events B o  +  - 5400 events, S/B = 4.1 B o  o  o 780 events, S/B = 0.3 Depending of assumptions on background and value of α : (from K. Honscheid)

46. with B d → ππ, B s → KK  relies on “U-spin” symmetry assumption (d  s), which is the only source of theoretical uncertainty  determination of and test of U-spin symmetry using measurements of from B s  J/ψϕ and β from B  J/ψ K S  sensitive to New Physics contribution by comparing with obtained from B s  D s K sensitivity in 1 year B    B S  K K

47. with B d → ππ, B s → KK  d, (d’, ’) parametrize P over T amplitude ratio  from B d  J/ψ K S, from Bs  J/ψϕ  exact U-spin symmetry => d = d’ ; = ’  3 unknowns and 4 measurements 1 year 2 years 3 years 4 years 95% confidence region for d and  σ γ after 4 years: 2.2º (for  = ~60º)

48. Rare B decays flavour changing neutral currents only at loop level very small BR ~ or smaller In the SM: Excellent probe of indirect effects of new physics! SM : BR ~ observation of the decay measurement of its BR CMS : 100 fb -1 (10 7 s at 10 34 cm -2 s -1 ) ~ 26 signal events 6.4 events background LHCb : 2 fb -1 ~ 33 signal events ~ 10 events background σ M = 38 MeV + - ,,

49. A. Ali et al., Phys. Rev. D61 074024 (2000) Rare B decays Forward-backward asymmetry can be calculated in SM and other models BTeV data compared to Burdman et al calculation

50. Conclusions LHCb and BTeV are second generation beauty CP violation experiments; They are well prepared to make crucial measurements in flavour physics with huge amount of statistics; Impressive number of different strategies for measurements of SM parameters and search of New Physics; CP violation is a cool research topic!! B factories established CP violation in the B sector and are making interesting measurements; Exciting times: understanding the origin of CP violation in the SM and beyond.