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A very charming decay in a beauty factory.

A very charming decay in a beauty factory. Internal Seminar December 7 th 2007. Kim Vervink - LPHE. Table of contents. The beauty factory: Accelerator Detector The very charming decay: Theoretical motivation Results Conclusions. 1. Tsukuba Mountain. Rice fields. Belle detector.

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A very charming decay in a beauty factory.

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  1. A very charming decay in a beauty factory. Internal Seminar December 7th 2007 Kim Vervink - LPHE K. Vervink

  2. Table of contents • The beauty factory: • Accelerator • Detector • The very charming decay: • Theoretical motivation • Results • Conclusions K. Vervink 1

  3. Tsukuba Mountain Rice fields Belle detector Main building Dormitory New Annex KEK laboratory K. Vervink 1

  4. KEKB vs LHC: accelerator • e+ e- collider • Just below the surface • Circumference = 3 km • 1 collision point -> 1 particle physics experiment • Start data taking 1999 • p+ p+ collider • Around 100m under the surface • Circumference = 27 km • 4 collision points -> 4 particle physics experiment • Start data taking 2008 K. Vervink 3

  5. KEKB vs LHC: accelerator • Asymmetric energy in 2 beams  facilitate proper time measurements • B0has b.g = 0.425 • E(e-:e+) = (8,0:3,5) GeV • ECMS(beam)= 10.58GeV = M(Y(4S)) ~ 2* M(B°) ~ 2* M(B+) < 2* M(Bs, …) • Lpeak = 1,7 x 1034 cm-2 s-1 • ~ 20 B’s per second! • Int. Lumi = 715 fb-1  Comparison to be made with Babar • Symmetric energy in 2 beams • E(p+:p+) = (7,0:7,0) TeV • ECMS(beam)= 14TeV  much more garbage • Lpeak = 2 x 1032 cm-2 s-1 • Int. Lumi = 0 fb-1  K. Vervink 4

  6. Belle: 13 nations, 57 institutes, ~400 collaborators PEP II accelerator for Babar detector. Babar: 11 nations, 80 institutes, 623 persons • Grand total: 460 fb-1 • Exceeded design luminosity by factor 4! 9GeV (e-)  3.1GeV (e+) peak luminosity: 1.211034cm-2s-1 PEPII Plan to maximize the delivered luminosity until the end of operations i.e. end of September 2008 8GeV (e-)  3.5GeV (e+) peak luminosity: 1.71034cm-2s-1 WORLD RECORD Babar K. Vervink

  7. Current and future plans of KEKB. Crab cavities • Motivation • beam-beam simulation predicts that luminosity will double • Beam test • 4.5 months dedicated machine time (Mid Feb. ~ end of June 2007) • Performance with crab crossing • Encouraging but not easy • Specific luminosity : ~ 30% higher • Bunch current limitation in beam life time • L ~ 1.06 x 1034cm-2s-1 y (beam-beam simulation) crab crossing 22mrad crossing K. Vervink 6

  8. Future plans of KEKB • Next milestone • Accumulation of 1000 fb-1 (715 fb-1 at present) • Near term plans • L = 2 x 1034cm-2s-1 • Benefits of crab crossing • Long-term future plan • SuperKEKB • Major upgrade plan of KEKB • Design luminosity: ~ 1036cm-2s-1 • Not yet approved (Construction hope to start in FY 2009) K. Vervink 7

  9. Belle detector. KLM counter: measures KL and muons Superconducting magnet (1.5T) 3.5GeV e+ Silicon vertex detector (SVD1 or SVD2) 8GeV e- Tracking + dE/dx small cell + He/C2H5 Electromagnetic calorimeter TOF counter Drift chamber: ¨Tracking + dE/dx small cell + He/C2H5 K. Vervink Aerogel Cherenkov cnt.

  10. Belle detector: some pictures K. Vervink 9

  11. Analysis Theory K. Vervink 10

  12. A very charming decay… B0 U(4S) Production e+ e- B0 • ECM = M(Y(4s)) ~ 2 M(B0) • In a symmetric accelerator 2 B’s would barely move. • Due to asymmetry of two beams •  Y(4) boosted in the forward direction • - B’s as well, but still hardly any opening angle. • Important for vertex reconstruction!! D*+ B0 D*- e- e+ Y(4S) B0 Without B mixing Branching fractions: Vcd V*cb Main interest of this decay: Clean CP analysis… K. Vervink 11

  13. CLAF Summer school Lecture R. Fleisher K. Vervink 12

  14. CLAF Summer school Lecture R. Fleisher K. Vervink 13

  15. CP violation in the mixing independent of decay of B CP violation in the decay CLAF Summer school Lecture R. Fleisher K. Vervink 14

  16. CLAF Summer school Lecture R. Fleisher K. Vervink 15

  17. SMALL!!! K. Vervink 16

  18. SMALL!!! SMALL!!! In the SM the penguin diagrams contribute in a few percent only. K. Vervink 17

  19. What do we remember: • Because “P/T” is estimated small in SM  very clean measurement of sin2b • No hadronic contamination • No contamination from other fases • What do we remember: • Because “P/T” is estimated small in SM  very clean measurement of sin2b • No hadronic contamination • No contamination from other fases • What do we remember: • Because “P/T” is estimated small in SM  very clean measurement of sin2b • No hadronic contamination • No contamination from other fases 2. The decay amplitude is CKM suppressed. Any NP in the penguins will right away show up! (This is not the case even in the golden channel!), but overall branching fraction is small. 3. One more parameter needs to be determined or sin2b will be diluted: h 2. The decay amplitude is CKM suppressed. Any NP in the penguins will right away show up! (This is not the case even in the golden channel!), but overall branching fraction is small. 3. One more parameter needs to be determined or sin2b will be diluted: h - A difference with J/yKS means a difference in penguin, not in mixing - A deviation from SM means 1. underestimation of penguins in SM 2. New physics - Effort should go into optimizing D*D* K. Vervink 18

  20. The time dependent decay rate: CP even and CP odd events need to be disentangled before CP fit => Angular analysis. K. Vervink 19

  21. Analysis: • Branching fraction & Yield: find events • 2. Angular analysis: fraction of CP-odd • 3. Lifetime fit: check resolution parameters • 4. CP analysis: for next meeting  K. Vervink 20

  22. History on Branching fraction X-check my analysis with Miyake-san’s: use same cuts! On the total data sample: find yield! K. Vervink 21

  23. X-check analysis: - first analysis I did - keep it simple - just a X-check, don’t waist too much time on it. K. Vervink 22

  24. Reconstructing the signal. Event shape Quality of tracks Kaon and pion tracks (with 4-momentum) Particle ID E, p constraints on p0 and Ks Combine to make D’s: if the mass corresponds (within XX MeV) Recalculate tracks with vertex and mass constraints: affects 4-momentum Combine to make D*’s: if the mass corresponds (within XX MeV) Best candidate selection Stronger constraints on mass windows Still per event many “candidate” B’s reconstructed While there can only be 1!!! Combine to make B’s: if the mass corresponds (within XX MeV) The B who’s D and D* mass has the smallest deviation from the nominal value (before any kinematical fits) K. Vervink 23

  25. Reconstructing the signal: reco. efficiency 1. Generate signal MC (B  D*+ D*-, B  …) 2. Simulate your detector (Pass through geant) 3. Output looks like real data 4. Reconstruct events (my code with previous cuts) How many events can you find back? - Fit distribution and distinguish between signal and combinatorial bkg (no other type of bkg) The same cuts  should give the same reconstruction efficiency K. Vervink 24

  26. Show signal in: K. Vervink 25

  27. Real data !! Experiment 07 – 27: data Miyake worked on (140 fb-1) Projection from 2D ML fit on DE and Mbc: K. Vervink 26

  28. Analysis on total data sample: - more channels included - PDF’s need to be more precise (more complex) - cuts stay roughly the same K. Vervink 27

  29. Experiment 7 – 55: total data sample Projection from 2D ML fit on DE and Mbc: Total data sample !! K. Vervink 28

  30. Analysis: • Branching fraction & Yield: find events • 2. Angular analysis: fraction of CP-odd • 3. Lifetime fit: check resolution parameters • 4. CP analysis K. Vervink 29

  31. Angular analysis: History Angular analysis: History K. Vervink 30

  32. How can we disentangle CP-odd from CP-even? Work in the transversity basis From the cosqtr and cosq1 distribution we can extract the three amplitudes From the cosqtr distribution we can extract the CP-odd fraction. K. Vervink 31

  33. Parametrize signal shape: Generate and simulate singal MC for each of the three polarisation, fit with a ponynomial. (reconstruction effects !!) A0 A A X-check with previous analysis: Background shape was determined from sidebands region of data. K. Vervink 32 cosqtr cosq1

  34. X-check of previous analysis • goal: find roughly same central value back (less channels, bit simplified) no need to optimize errors • constant signal over background fraction from 2D DE and Mbc fit. • simultanious fit on cosqtr and cosq1 my result: previous result: K. Vervink 33

  35. Angular analysis on total data sample. • Optimize procedure to reduce statistical error. • A more complicated (more correct) PDF was defined: • Unbinned ML fit • Only on cosqtr (simplified so other technical • Features could be included (toy MC approved) • Event by event signal over background fraction • Background shape of cosqtr determined during fit • Reconstruction efficiency per polarization K. Vervink 34

  36. Analysis: • Branching fraction & Yield: find events • 2. Angular analysis: fraction of CP-odd • 3. Lifetime fit: check resolution parameters • 4. CP analysis K. Vervink 35

  37. K- ps0 p- D* p+ D* p+ ps+ p- Lifetime fit. B’s are produced in a boosted frame  Dt is measured from vertexpositions K. Vervink 36

  38. Lifetime fit: resolution parameters • Lifetime is well known. • This is more a resolution parameter test. • Same param’s are used in CP-fit!! Detector resolution, vertex reconstruction …. Resolution parameters are determined by Vertex group for a “general decay”. I have more tracks than “general” decays: differences possible! If difference is too big: determine parameters myself but syst. error will go up!! K. Vervink 37

  39. X-check analysis. K. Vervink 38

  40. X-check analysis. Signal shape: Background shape determined from the sideband region. K. Vervink 39

  41. X-check analysis: small data sample Experiment 07 – 27: data Miyake worked on (140 fb-1) K. Vervink 40

  42. Angular analysis on total MC sample. 10% deviation with standard parameters need to be investigated!! Although ……. K. Vervink 41

  43. Comparison with D+D- study Background shape from sideband region. K. Vervink 42

  44. Angular analysis on total data sample. # events: Kim: 509 Sasa: 104 Miyake: 127 K. Vervink 43

  45. Analysis: • Branching fraction & Yield: find events • 2. Angular analysis: fraction of CP-odd • 3. Lifetime fit: check resolution parameters • 4. CP analysis K. Vervink 44

  46. Status of the CPfit: 1. X-check with previous analysis is harder (old software that is lost…) , but still satisfying enough result. 2. Many checks need to be done before looking on data: - large Toy MC (linearity and bias tests) - generic MC 3. Before looking on data: approval from 3 internal Belle referees 4. Do fit on data 5. Present on conferences  6. Write things down K. Vervink 45

  47. Summary 1. We have a beautiful factory: Belle is an exciting “living” experiment to work on now! 2. With some very charming decays Clean observation of CP violating parameters are possible (with enough data) 3. 454 data BD*D* data events on total sample 4. 11.6 +/- 0.04 % CP-odd fraction 5. Resolution parameters established well enough for CP fit and lifetime fit. (B lifetime: 1.593 +/- 0.097) 6. Working on CP-fit K. Vervink 46

  48. The end. Tnx to Olivier for making my channel silver  Tnx to Nicolas for the Feynman diagrams Tnx to Mathias for the special effects  K. Vervink 11

  49. Extra K. Vervink

  50. K. Vervink 11

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