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Flavour-specific asymmetry and LHCb

Flavour-specific asymmetry and LHCb. Robert W. Lambert On behalf of the LHCb collaboration. Introduction. D  exclusive asymmetry hep-ex 0904.3907 D  Inclusive asymmetry hep-ex 1005.2757 What can we do at LHCb ?. Literature. Reading material: LHCb

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Flavour-specific asymmetry and LHCb

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  1. Flavour-specific asymmetryand LHCb Robert W. Lambert On behalf of the LHCb collaboration CERN CPV, 18th June 2010

  2. Introduction D exclusive asymmetry hep-ex 0904.3907 D Inclusive asymmetry hep-ex 1005.2757 What can we do at LHCb? CERN CPV, 18th June 2010

  3. Literature • Reading material: • LHCb • CERN-LHCb-2007-054 Public note from old Monte Carlo • CERN-THESIS-2008-045 Paul’s Thesis • CERN-THESIS-2009-001 Rob’s Thesis • CERN-THESIS-2010-076 Ken’s Thesis • Theory • hep-ph 0406300 U. Nierste • hep-ph 0612167[JHEP] A. Lenz, U. Nierste • hep-ph 0605028[PRL] Y. Grossman et al. • hep-ph 0604112[PRL] Z. Ligetiet al. • Other measurements • hep-ex 0505017[PRD] Belle • hep-ex 0202041[PRL] Babar • hep-ex 0101006[PRL] Cleo • Note 9015 CDF inclusive CERN CPV, 18th June 2010

  4. Outline Theory .. from an experimentalist Experimental Status Complications at LHCb Why LHCb? Measurements at LHCb Real data highlights Outlook and Prospects Conclusions CERN CPV, 18th June 2010

  5. Flavour-specific asym. • Flavour-specific decays • Favoured/Allowed • Not allowed at tree • Through mixing • Flavour specific asymmetry, afs, parameterises CPV in mixing CERN CPV, 18th June 2010

  6. The whole shebang Three different parameters fully constrain b-mixing afs is very small in the standard model CERN CPV, 18th June 2010

  7. Discovery Potential ? • afs is sensitive to new physics (NP): • Sensitive to loop contributions • Sensitive to new CPV phases • If we allow a single NP phase in the mixing  CERN CPV, 18th June 2010

  8. Discovery Potential ? • afs is sensitive to new physics (NP): • Sensitive to loop contributions • Sensitive to new CPV phases • If we allow a single NP phase in the mixing  CERN CPV, 18th June 2010

  9. Discovery Potential ? • afs is sensitive to new physics (NP): • Sensitive to loop contributions • Sensitive to new CPV phases • If we allow a single NP phase in the mixing  • Up to 200-times the SM ... but ... (4x10-3)< D measurement CERN CPV, 18th June 2010

  10. Experimental Status CERN CPV, 18th June 2010

  11. B-factories hep-ph 0605028 n m- b b c c b m- n • Babar, Belle, Cleo all use the di-muon sample • Know the initial state (4S) • Time-integrated number-counting of di-muons • Possible muondetector asymmetry is important to measure CERN CPV, 18th June 2010

  12. Exclusive measurement hep-ex 0904.3907 n m- Bs Bs Ds+ • D have also made an exclusive measurement • Search for the full decay chain in the data • Requires full reconstruction • Flavour-tagging provides extra information • Lower and more easily understood backgrounds • Extra detector asymmetry • Lower statistics CERN CPV, 18th June 2010

  13. CDF Inclusive Note 9015 n m- b b c c b m- n • CDF use only the di-muon sample • Don’t know the initial state (pp) • Time-integrated number-counting • Possible muondetector asymmetry is important to measure CERN CPV, 18th June 2010

  14. New D inclusive hep-ex 1005.2757 n m- b b c c b m- n CERN CPV, 18th June 2010 • D used primarily the di-muon sample • Don’t know the initial state (pp) • Time-integrated number-counting • Possible muondetector asymmetry is important to measure

  15. New D inclusive hep-ex 1005.2757 • Key Systematics (it’s difficult to be inclusive!) • Kaons decaying in-flight • Punch-through of hadrons to muons • Key methods • Rely on real data, cross-check with well-tuned Monte Carlo • Use the inclusive single muon sample to get extra information • Reverse magnets to remove most detector asymmetry • Do many many cross-checks in different phase-space regions • Result, 3.2s ! CERN CPV, 18th June 2010

  16. Summary • Before the New D Inclusive Measurement • A lot of measurements • All consistent with SM +/- 1% • The New D Inclusive Measurement • First evidence of departure from the SM • Statistics-limited, so may improve over the next year • A lot of theory interest , so, how will LHCb help? • ... The situation is significantly more complicated ... CERN CPV, 18th June 2010

  17. Complications CERN CPV, 18th June 2010

  18. The simple formula 10-3 -> 10 -5 CERN CPV, 18th June 2010

  19. The simple formula Very Complicated • Polluting asymmetries are much larger than afs • Detector asymmetrydc ~(10-2) • Production asymmetrydp~(10-2) • Background asymmetrydb~(10-3) 10-3 -> 10 -5 10 -2 10 -2 10 -3 CERN CPV, 18th June 2010

  20. LHCb CERN CPV, 18th June 2010

  21. Detector Asymmetry, dc 120 K-, p . 100 K+, p 80 hadronic cross-section / mb 60 40 20 0 0.1 1 10 100 1000 momentum in lab frame P / GeV c lab MC Asymmetry in Muons Kaon interaction cross-section Left Right PDG K- p K+ p Kaon PDG cross-section After 4Tm Magnet +ve -ve -1 CERN CPV, 18th June 2010 • Matter detector hadronic interactions are asymmetric • Magnet divides +/- charge, allowing +/- detector asymmetry • We need to reverse the magnet regularly

  22. LHC CERN CPV, 18th June 2010 An amazing machine Unfortunately also not CP symmetric

  23. Production Asymmetry,dp Explicitly asymmetric at LHC dp(B0 and B0) Pythia Valence Quark Scattering LHC is a proton-proton collider: not CP-symmetric LHCb is at high rapidity where production asymm. are largest There is never a simple control channel to measure dp CERN CPV, 18th June 2010

  24. Why LHCb? CERN CPV, 18th June 2010

  25. Why LHCb? LHCb is a dedicated, precision, b-physics experiment More statistics: we’re in the forward region, and at LHC CERN CPV, 18th June 2010

  26. Being Timely Proper Time: LHCbVelo precise down to 35 fs! CERN CPV, 18th June 2010

  27. Being Precise RICH 1 (Vertical) RICH 2 (Horizontal) TT MAGNET T1-T3 Particle ID: separation handled by dedicated subdetectors Two RICHes, Calorimetry and Muon system CERN CPV, 18th June 2010

  28. Being Exclusive Monte-Carlo! ~100k Ds in 5 fb-1 ~100k Ds in 0.05 fb-1 Our forte: exclusive, reconstructed, b-decays In particular, time-dependent measurements CERN CPV, 18th June 2010

  29. Measurements CERN CPV, 18th June 2010

  30. Measurements Inclusive Exclusive Subtraction method combine and CERN CPV, 18th June 2010

  31. Inclusive at LHCb ~108 per fb-1 • Channel • Measured by D (see earlier) • Complications • Physics! • Production asymmetry: N(b)≠N(anti-b) [in acceptance] • Pythia predicts dp(b) = • Mitigating factors • None, difficult to interpret this measurement CERN CPV, 18th June 2010

  32. Inclusive at LHCb ~108 per fb-1 • Channel • Measured by D (see earlier) • Complications • Physics! • Production asymmetry: N(b)≠N(anti-b) [in acceptance] • Pythia predicts dp(b) = • Mitigating factors • None, difficult to interpret this measurement CERN CPV, 18th June 2010

  33. Hadronic at LHCb CERN-THESIS-2008-045 CERN-LHCb-2007-017 ~105 per fb-1 Monte-Carlo! Channel CERN CPV, 18th June 2010

  34. Hadronic at LHCb CERN-THESIS-2008-045 CERN-LHCb-2007-054 ~105 per fb-1 • Channel • Measures • Complications • Must fix either dc or dp in the fit – (db can be fit beforehand) • Mitigating factors • Detector asymmetry small ~10-4 • Fit afs and dp. – With excellent proper time resolution (35 fs) CERN CPV, 18th June 2010

  35. Hadronic at LHCb CERN-THESIS-2008-045 CERN-LHCb-2007-054 ~105 per fb-1 • Channel • Measures • Complications • Must fix either dc or dp in the fit – (db can be fit beforehand) • Mitigating factors • Detector asymmetry small ~10-4 • Fit afs and dp. – With excellent proper time resolution (35 fs) CERN CPV, 18th June 2010

  36. Semi-leptonic CERN-LHCb-2007-054 ~106 per fb-1 Monte-Carlo! Monte-Carlo! Channel (q = s/d) CERN CPV, 18th June 2010

  37. Semi-leptonic CERN-LHCb-2007-054 ~106 per fb-1 • Channel (q = s/d) • Measures • Complications • Missing neutrino makes proper-time resolution worse (≥120 fs?) • Detector asymmetry large and difficult to measure • Mitigating factors • Lots of statistics, but this makes dc even more important CERN CPV, 18th June 2010

  38. Semi-leptonic CERN-LHCb-2007-054 ~106 per fb-1 • Channel (q = s/d) • Measures • Complications • Missing neutrino makes proper-time resolution worse (≥120 fs?) • Detector asymmetry large and difficult to measure • Mitigating factors • Lots of statistics, but this makes dc even more important CERN CPV, 18th June 2010

  39. The subtraction method • Take Bs/Bd with the same final states ( =KKp m) • Background asymmetry: 2D fit in mass spectra • Production asymmetry: fit with proper-time dependence • Detector asymmetry: the same in each decay… • Do a simultaneous time-dependent fit • Measure the difference between Bs and Bd • Very comparible to the D measurement, but orthogonal to it! CERN CPV, 18th June 2010

  40. The subtraction method • Take Bs/Bd with the same final states ( =KKp m) • Background asymmetry: 2D fit in mass spectra • Production asymmetry: fit with proper-time dependence • Detector asymmetry: the same in each decay… • Do a simultaneous time-dependent fit • Measure the difference between Bs and Bd • Very comparible to the D measurement, but orthogonal to it! CERN CPV, 18th June 2010

  41. Real data highlights CERN CPV, 18th June 2010

  42. Real Data Bs ~800 mb-1 PV Bs SV m- Ds+ TV LHCb Preliminary p+,K+,K- EVT: 49700980 RUN: 70684 mm CERN CPV, 18th June 2010

  43. Real Data Bd LHCb Preliminary K-,K+,p+ ~800 mb-1 TV D+ SV PV m- Bd EVT: 141526660 RUN: 70666 mm CERN CPV, 18th June 2010

  44. All D(s)->KKp ~2.6 nb-1 n.b. Selection with no requirement for a muon (need ~40 nb-1) CERN CPV, 18th June 2010

  45. Sensitivities and Outlook CERN CPV, 18th June 2010

  46. Sensitivity estimates All MC predictions!! Real data will be worse • Full MC used to tune toy MC • Massive toy MC studies done in: • CERN-LHCb-2007-054 • CERN-THESIS-2008-045 • CERN-THESIS-2009-001 • Scaled to: • Latest Monte Carlo efficiencies • s(bb) = 500 mb CERN CPV, 18th June 2010

  47. Current Results fs fs CERN CPV, 18th June 2010

  48. After 1fb-1 of LHCb fs Assume Ab central value and no NP in Bd fs CERN CPV, 18th June 2010

  49. c.f. J/YF hep-ph 0612167 • Directly Measure sin fs • s(fs) = 0.05c in 1 fb-1 • Effectively Measures • s() = 0.5c in 1 fb-1 • But they constrain NP differently • Effective power enhanced • NB physical limit of afs is at 4x10-3 < current D result! Current measurements (pre D0 paper) Red : Dms Yellow: DGs Black: fs Blue: afs CERN CPV, 18th June 2010

  50. Combining D CERN CPV, 18th June 2010

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