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Oscillazioni del mesone D 0

Oscillazioni del mesone D 0. Gianluca Cavoto INFN Roma La Sapienza Commissione Scientifica Nazionale I Roma, 3 aprile 2007. Outline. Neutral mesons flavor oscillation Charm meson mixing Evidence from B-factories D 0     + D 0    l   l , D 0   s  +  - , D 0   +  -  +  -

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Oscillazioni del mesone D 0

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  1. Oscillazioni del mesone D0 Gianluca Cavoto INFN Roma La Sapienza Commissione Scientifica Nazionale I Roma, 3 aprile 2007 Gianluca Cavoto

  2. Outline • Neutral mesons flavor oscillation • Charm meson mixing • Evidence from B-factories • D0+ • D0ll, D0s+-, D0+-+- • Outlook Gianluca Cavoto

  3. Neutral Mesons systems • Two-level system (M0,M0) • Weak interactions remove degeneracy, make them unstable Gianluca Cavoto

  4. Neutral mesons oscillations Time evolution for meson of known flavor at t=0 An opposite flavor component appears after a while! M0 “oscillates” into M0! (also dubbed “mixing”) Gianluca Cavoto

  5. Some visual examples Probability to find a M0(M0) after a given time Lifetime units Gianluca Cavoto

  6. How to generate this ?? No tree level Flavor Changing Neutral Currents (FCNC) in SM Gianluca Cavoto

  7. Can you see New Physics ? B0 mixing was argued by UA1 and directly observed by ARGUS in 1987 And the top was discovered 8 years after! Large mixing frequence implied t quark was heavy (mt > 50 GeV/c2) Gianluca Cavoto

  8. Even more ambitious today! Bd,s (K) mixing on the punch line for virtual effects from NP Not only x and y but also phases in the mixing CP violation Gianluca Cavoto

  9. The missing tile Gianluca Cavoto

  10. Charm Meson Mixing Gianluca Cavoto

  11. Short and Long distance • Prediction x and y x VIRTUAL states Sum of intermediate REAL states y Gianluca Cavoto

  12. SM prediction for charm mixing Always hard to evaluate SU(3) breaking !!! (HQET, propagation of common hadronic states,…) SU(3) breaking effect more important for y bottom quark ruled out by VCKM Box diagram contribution Naively Gianluca Cavoto

  13. New Physics in Charm ? Hard to see a clear cut Pushing the limit down excludes models Try to separate x and y! 2006 limit Gianluca Cavoto

  14. Experimental Searches Gianluca Cavoto

  15. Charm physics with B-factory • Run1-5, more than 500M cc events Run1-5 Gianluca Cavoto

  16. The technique Gianluca Cavoto

  17. Flavor tagging • Same flavour: Wrong-Sign (WS)mixing may have occured • Opposite flavour: Right-Sign (RS)unmixed events Flavor at production Flavor at decay Gianluca Cavoto

  18. Double-Cabibbo Suppressed Decays Vus V*ud V*cd Vcs Gianluca Cavoto

  19. Time evolution  is the (relative) strong phase WS (relative to RS) time-dep. rate(small x and small y limit) RM Gianluca Cavoto

  20. Event Selection Gianluca Cavoto

  21. RS and WS data set Gianluca Cavoto

  22. Decay time analysis • Resolution function from RS sample Selection criteria Gianluca Cavoto

  23. Background components Discrimination power from m() and m Gianluca Cavoto

  24. Signal extraction 384 fb-1 Gianluca Cavoto

  25. RS decay time analysis D0 lifetime and time resolution function from RS sample Gianluca Cavoto

  26. WS decay time with mixing 384 fb-1 Gianluca Cavoto

  27. Evidence for D0 mixing! Best fit solution 3.9  Gianluca Cavoto

  28. Validation: m() and m fit in t bins Gianluca Cavoto Relative rate of WS events clearly increases with time

  29. Validation: fit RS for mixing Gianluca Cavoto

  30. Systematics uncertainty Gianluca Cavoto

  31. Systematics on Decay time Gianluca Cavoto

  32. Allowing for CP violation CP asymmetry in DCSD ! Gianluca Cavoto

  33.  analysis from Belle Gianluca Cavoto

  34. More evidence…! Gianluca Cavoto

  35. Belle evidence on yCP “Apparent” lifetime difference between D0-+ and +-, +- D= mixing phase Gianluca Cavoto

  36. Results on yCP • Plot di combinazioni Belle hep-ex/0703036 Gianluca Cavoto

  37. Separating x and y •  only cannot separate x and y Need info on strong phases • Multibody decays:Dalitz models D0K- DCS CF DCS decays proceed primarily through K*+- while CF through K-+ Gianluca Cavoto

  38. D0  Select special region of Dalitz plot Effective phase Gianluca Cavoto

  39. D0KS Both flavor (K*-+/K*+-) final states in the same Dalitz plot! CP-eigenstate (KS) and flavor states (K*-+) in the same Dalitz plot! Gianluca Cavoto

  40. D0KS Dalitz model Gianluca Cavoto

  41. Belle D0KS results Gianluca Cavoto

  42. D-mixing with Semileptonic decay D0ll No DCS sl. ! Gianluca Cavoto

  43. Summary and Outlook Gianluca Cavoto

  44. Summary • BaBar updating multibody decays analysis, yCP measurements • BaBar KS on-going y Gianluca Cavoto

  45. Interpreting the results D0 and D0 Ciuchini et al. hep-ph/0703294 68% 95% HFAG PRELIMINARY Gianluca Cavoto

  46. Measuring  To beat down the model systematics measure phases directly Gianluca Cavoto

  47. Double tag at (3770) [CLEO-c] Need to run On threshold DCP± neutral D CP eigenstate (3770) decayconserves CP Gianluca Cavoto

  48. And CP violation? In general NP weakly constrained if SM not known Nevertheless SUSY coupling can be constrainedhints on squark and gluino masses! Neutral meson mixing always a window into unknown (virtual) states! Ciuchini et al. hep-ph/0703294 Gianluca Cavoto

  49. Back up slides Gianluca Cavoto

  50. Fit signal MC events Gianluca Cavoto

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