Selected Rare Decays

Transcription

1 Introduction Theory Experiment Prospects Conclusion as evidence of new physics University of Oklahoma: Homer L. Dodge Dept of Physics 7 November 2012

2 Introduction Theory Experiment Prospects Conclusion Outline Introduction Theory Trees & Loops Branching Ratios Suppression FCNC Suppression Helicity Suppression Experiment Prominent B Decays Decay Detection LHCb Results Prospects Conclusion

3 Introduction Theory Experiment Prospects Conclusion Introduction The Standard Model (SM): Current substantiated theory of what the world is & what holds it together Quarks Baryons: qqq, q q q Mesons: q q 3 gen, 6 flavors, 8 colors Leptons 3 gen, 6 flavors Color less Gauge Bosons (W ±, Z 0, g, γ, H 0 )

4 Introduction Theory Experiment Prospects Conclusion Introduction The Standard Model (SM): Current substantiated theory of what the world is & what holds it together Quarks Leptons Gauge Bosons (W ±, Z 0, g, γ, H 0 ) Fermions: 1 Integral spin 2 Bosons: Integral spin

5 Introduction Theory Experiment Prospects Conclusion Introduction Rare decays: so uncommon that they are hard to observe help in the search for physics beyond the standard model observable with powerful computing power, high energy / luminosity collisions

6 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Theory

7 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Theory: Tree and loop level decays In the SM, decays occur at the tree level and through loops.

8 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Theory: Tree and loop level decays In loops, virtual intermediary particles interact at short time scales The two types of loops discussed in this talk are box and penguin (FCNC) loop diagrams E t E m m t

9 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Theory: Tree and loop level decays In loops, virtual intermediary particles interact at short time scales The two types of loops discussed in this talk are box and penguin (FCNC) loop diagrams E t E m m t

10 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Theory: Tree and loop level decays In loops, virtual intermediary particles interact at short time scales The two types of loops discussed in this talk are box and penguin (FCNC) loop diagrams E t E m m t

11 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Calculating the Branching Ratio Calculating the branching ratio (BR) first requires calculation of the decay width, by finding the matrix elements: Γ = τ M 2 (1) M 2 = i M i 2 (2) For example: B s µ + µ occurs via 15 different particle combinations: M 2 = M 1 + M 2 + M 3 + M 4 + M 5 +M 6 + M 7 + M 8 + M 9 + M 10 +M 11 + M 12 + M 13 + M 14 + M 15 2 = M M 1 M2 + M 1 M3 + M 1 M4 +M 1 M 5 +M 1 M 6 +M 1 M 7 +M 1 M

12 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Calculating the Branching Ratio Calculating each matrix element can be done either with Wick contractions or Feynman diagrams. Using Feynman diagrams, follow the reverse fermion line:

13 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Calculating the Branching Ratio M 1 M 4 = s s d 4 l d 4 l (2π) 4 (2π) (3) 4 Tr[u(p 4 )ū(p 4 ) ig 2 2 γµ (1 γ 5 i( l p 4 ) ig ) (l p 4 ) 2 + iɛ 2 2 γν (1 γ 5 ) v(p 3 ) v(p 3 ) igγλ cos θ w (g µ Z + g µ A γ5 )] Tr[u(p 1 )ū(p 1 ) ig 2 2 γα (1 γ 5 i( l + p 2 + m t ) ig )V ts (l + p 2 ) 2 m t iɛ 2 2 γβ (1 γ 5 )V bt v(p 2 ) v(p 2 )] W ρν W µσ W αγ W βɛ W λδ W δγɛ...a nontrivial effort to calculate M 2! (Variables and couplings defined in Barger & Phillips Collider Physics)

14 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Calculating the Branching Ratio Then use that partial decay width Γ from the amplitude M 2, compared to the decay width (Γ) due to all possible decay modes, to find the branching ratio: BR[Γ 1mode ] = Γ 1mode i=modes Γ i (4)

15 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Calculating the Branching Ratio Then use that partial decay width Γ from the amplitude M 2, compared to the decay width (Γ) due to all possible decay modes, to find the branching ratio: BR[Γ 1mode ] = Γ 1mode i=modes Γ i (4) For example, the Bs 0 particle decays to µ + µ only a tiny fraction of the time, as calculated by: BR(B 0 s µ + µ ) = Γ(B 0 s µ + µ ) Γ(B 0 s D s X ) + Γ(B 0 s lν l X ) +... (5)

16 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Calculating the Branching Ratio Decay width: Quantum mechanical uncertainty of decaying energy due to the finite lifetime of the particle E t

17 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Suppressed Decays: FCNC What makes certain decays rare? 1. Flavor-changing neutral currents don t occur in SM tree level Only W changes flavor. So one fermion cannot decay directly into another of the same charge but different flavor. Each vertex contributes a (coupling factor) 2 less than one to M 2 : more vertexes = less common decay No tree level contribution won t drown out possible loop level new physics contribution!

18 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Suppressed Decays: Helicity Suppression What makes certain decays rare? 2. Conservation of angular momentum suppresses certain helicity combinations Helicity: H = σ ˆp

19 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Suppressed Decays: Helicity Suppression What makes certain decays rare? 2. Conservation of angular momentum suppresses certain helicity combinations Helicity: H = σ ˆp Chirality: intrinsic handedness Helicity always matches chirality for massless particles

20 Introduction Theory Experiment Prospects Conclusion Trees & Loops Branching Ratios Suppression Suppressed Decays: Helicity Suppression For example: Bs 0 spin=0 µ and µ + must have opposite spins µ s must both be left or right-handed W only interacts with L particles and R anti-particles So the decay requires µ + with R chirality but L helicity m µ + 0 so can occur, but very small chance of it, especially when µ + has relativistic levels of momentum Adds helicity suppression factor of ml 2/m2 B (m2 2 µ/m B s )

21 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Experiment: B 0 (s) µ+ µ

22 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Prominent B Decays: B 0 (s) µ+ µ

23 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Prominent B Decays: B 0 (s) µ+ µ Recent results BR SM (B 0 s µ + µ ) = 3.2 ± BR SM (B 0 d µ + µ ) = 0.10 ± CDF: 2008 Upper bound (95% CL) BR CDF (B 0 s µ + µ ) < DØ: 2010 Upper bound (95% CL) BR DØ (B 0 s µ + µ ) < CDF: 2011 Excess observed (90% CL) < BR CDF (B 0 s µ + µ ) < CMS: 2012 Tighter bounds (95% CL) BR CMS (B 0 s µ + µ ) < BR CMS (B 0 d µ+ µ ) <

24 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ The LHCb is designed to detect B mesons

25 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ

26 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

27 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

28 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

29 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ

30 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

31 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

32 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

33 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

34 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

35 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

36 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

37 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

38 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors F = q v B = m ac qvb = mv 2 p/p = 0.4% at 5 GeV/c r qrb = p p/p = 0.6% at 100 GeV/c

39 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

40 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

41 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

42 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

43 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

44 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ VELO RICH Magnet Tracking system Calorimeters Muon detectors

45 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation

46 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation {Depends on PV, SV, IP, L, p T, m µµ, τ}

47 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation HLT Triggers: 1-µ events with p T > 1.5 GeV/c 2-µ events with p T 1 p T 2 > 1.3 GeV/c All tracks must have p T > 0.5 GeV/c Software Triggers: 1-µ events: IP> 0.1 mm, p T > 1.0 GeV/c 2-µ events: m µµ > 4700 MeV/c 2 SV (muons) displaced from PV: L/σ L > 15 All tracks: p < 500 GeV/c and 0.25 < p T < 40 GeV/c B decay time < 9 τ p T (B) 500 MeV/c Main remaining background: b b µ + µ X

48 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation MVS with a BDT removes 80% of background, while keeping 92% of the signal Efficiency checked by running same algorithms on normalization modes: B + J/ψK + B 0 s J/ψ φ B 0 K + π ( main control sample) According to simulation, efficiencies of signal and normalization modes agree within 0.2%

49 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation Selected muon pairs that pass triggers and MVS go through BDT to assess probability of being signal, based on: B IP IP/σ IP Degree of isolation of the pair B candidate decay time, p T, and measure of isolation Distance of closest approach of muons p T,min of the muon pair cos θ, θ=angle between p µ and plane of p B and beam axis Result in binned # vs m µµ (following)

50 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Probability of Being Signal vs BDT Output:

51 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results 0 LHCb Results: B(s) µ+µ LHCb Results for Bs0 µ+ µ :

52 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: BR = BR norm ɛ norm ɛ sig f norm f d(s) N B(s) µ+ µ N norm Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation BR norm : branching fraction of normalization channel ɛ sig, ɛ norm : efficiencies of signal/normalization channels f d(s) : probability of a b quark fragmenting into a B 0 (s) particle f norm : product of probabilities of b fragmenting into each normalization mode N norm : # signal events in normalization channels Final BR uses the weighted average of BR due to each of the three normalization channels

53 Introduction Theory Experiment Prospects Conclusion Prominent B Decays Decay Detection LHCb Results LHCb Results: B 0 (s) µ+ µ LHCb: 2012 Tightest bounds yet, at 95% (90%) CL BR LHCb 2011 (Bs 0 µ + µ ) < BR LHCb 2010&2011 (Bs 0 µ + µ ) < 4.5 (3.8) 10 9 BR LHCb 2010&2011 (Bd 0 µ + µ ) < 1.0 (0.81) 10 9 Compared to the SM: BR SM (Bs 0 µ + µ ) = 3.2 ± BR SM (Bd 0 µ + µ ) = 0.10 ± Compared to CDF Excess: < BR CDF (Bs 0 µ + µ ) <

54 Introduction Theory Experiment Prospects Conclusion Current Prospects: B 0 (s) µ+ µ B meson research continues at the LHCb The LHCb hopes to reach the SM level of precision for this decay with the 2012 data

55 Introduction Theory Experiment Prospects Conclusion Current Prospects: B 0 (s) µ+ µ More precise measurement also helps constrain natural SUSY models:

56 Introduction Theory Experiment Prospects Conclusion Results are approaching SM precision, but we re not there yet...

57 Introduction Theory Experiment Prospects Conclusion Conclusion Rare decays make excellent windows to understand the search for physics beyond the SM. While these results are approaching SM values, the process gives a helpful precedent for additional rare decay experiments.

58 Introduction Theory Experiment Prospects Conclusion Conclusion Rare decays make excellent windows to understand the search for physics beyond the SM. While these results are approaching SM values, the process gives a helpful precedent for additional rare decay experiments.

59 Introduction Theory Experiment Prospects Conclusion References P. Preuss, March of the Penguins, Lab (2008) (URL: A. J. Buras, hep-ph/ (1998). F. Tanedo, Quantum Diaries: The Birds and the Bees, Quantum Diaries (2011) (URL: V. D. Barger and R. Phillips, Collider Physics, U of WI-Madison, Westview Press (1991). S. L. Glashow, J. Iliopoulos and L. Maiani, Phys. Rev. D, 2, 1285 (1970). F. Tanedo, Helicity, Chirality, Mass, and the Higgs, Quantum Diaries (2011) (URL: T. C. Dönszelmann et al. (BaBar Collaboration), Particles and Nuc. Int l Conf., SLAC-PUB (2005). M. Bando et al., Z. Phys. C - Particles and Fields 12, (1982). V. M. Abazov et al. (DØ Collaboration), Phys. Lett. B 693, 539 (2010). T. Aaltonen et al. (CDF Collaboration), Phys. Rev. Lett. 107, (2011). S. Chatrchyan et al. (CMS Collaboration), JHEP 1204, 033 (2012). S. Chatrchyan et al. (CMS Collaboration), Phys. Rev. Lett. 107, (2011). R. Aaij et al. (LHCb Collaboration), Phys. Rev. Lett. 108, (2012). R. Aaij et al. (LHCb Collaboration), Phys. Lett. B 708, 55 (2012). R. Aaij et al. (LHCb Collaboration), Phys. Lett. B 699, (2011). LHCb Collaboration et al., JINST 3 S08005 (2008). LHCb Collaboration, LHCb Strongly Squeezes SUSY Parameter Space, Large Hadron Collider beauty experiment (2012) (URL: A. Phan (LHCb Collaboration), What Made Those Tracks, Quantum Diaries (2012) (URL: bdt R. Aaij et al. (LHCb Collaboration), Phys. Lett. B 708, 55 (2012). P. Speckmayer, A. Hocker, J. Stelzer, and H. Voss, J. Phys. Conf. Ser. 219, (2010). A. Abulencia et al. (CDF Collaboration), Phys. Rev. Lett. 95, (2005). R. Aaij et al. (LHCb Collaboration), Phys. Rev. D 85, (2012). H. Murayama, Supersymmetry phenomenology, hep-ph/ (2000). P. Bechtle, T. Bringmann, K. Desch, H. Dreiner, M. Hamer, C. Hensel, M. Kramer and N. Nguyen et al., JHEP 1206, 098 (2012).

60 Introduction Theory Experiment Prospects Conclusion

61 Introduction Theory Experiment Prospects Conclusion K + π + ν ν

62 Introduction Theory Experiment Prospects Conclusion Relevant Kaon Decays Rare Kaon Experiments: Forbidden decays: Searches for decays explicitly forbidden by the standard model, such as lepton flavor violation (LFV) Suppressed decays: Measurements of standard model parameters, such as that of suppressed decays, looking for new physics by comparison with SM parameters Conservation law violating decays: The study of CP violation Low energy QCD perturbation theory (strong interactions)

63 Introduction Theory Experiment Prospects Conclusion Relevant Kaon Decays Rare Kaon Experiments: Forbidden decays: Searches for decays explicitly forbidden by the standard model, such as lepton flavor violation (LFV) Suppressed decays: Measurements of standard model parameters, such as that of suppressed decays, looking for new physics by comparison with SM parameters Conservation law violating decays: The study of CP violation Low energy QCD perturbation theory (strong interactions)

64 Introduction Theory Experiment Prospects Conclusion Relevant Kaon Decays Rare Kaon Experiments: Forbidden decays: Searches for decays explicitly forbidden by the standard model, such as lepton flavor violation (LFV) Suppressed decays: Measurements of standard model parameters, such as that of suppressed decays, looking for new physics by comparison with SM parameters K + π + ν ν Conservation law violating decays: The study of CP violation Low energy QCD perturbation theory (strong interactions)

65 Introduction Theory Experiment Prospects Conclusion Relevant Kaon Decays: K + π + ν ν

66 Introduction Theory Experiment Prospects Conclusion Relevant Kaon Decays: K + π + ν ν E-747: Two events observed: 211 < p π + < 230 MeV/c[?,?] E-949: One event observed: 211 < p π + < 230 MeV/c[?] Three events observed: 140 < p π + < 199 MeV/c[?,?] Funding cut BR E747,E949 = (6) BR SM = (8.1 ± 1.1) (7) Arbitrary units π + π π + (0.056) π + π 0 π 0 (0.018) π + π e + ν ( ) π 0 e + ν (0.051) π 0 µ + ν (0.034) π + π 0 (0.21) Momentum (MeV/c) µ + ν (0.64)

67 Introduction Theory Experiment Prospects Conclusion Relevant Kaon Decays: K + π + ν ν E-949: Shut down by funding cuts J-PARC & NA62 in progress

68 Introduction Theory Experiment Prospects Conclusion Kaon Decay Detection: E-949

69 Introduction Theory Experiment Prospects Conclusion Kaon Decay Detection: E-949

70 Introduction Theory Experiment Prospects Conclusion Kaon Decay Detection: E-949 Beam counter measures ratio of K + to π + BeO degrader slows down K + to MeV/c 1T solenoid magnetic field in the beam pipe direction stops K + in a scintillating target, stopping peak cm into the target Coincidence delay (> 2 ns) vetos background pions from beams or K + that decay in flight Charged decay products tracks identified with drift chamber Charged decay products stopped by scintillator counters Photons detected with a lead-scintillator detector around barrel and two endcaps Pions stopped in layers of scintillators

71 Introduction Theory Experiment Prospects Conclusion Current and Future Prospects: K + π + ν ν J-PARC and NA-62 preparing for additional data taking

72 Introduction Theory Experiment Prospects Conclusion

73 Introduction Theory Experiment Prospects Conclusion Backup Slides

74 Introduction Theory Experiment Prospects Conclusion K + Decay Modes

75 Introduction Theory Experiment Prospects Conclusion K L Decay Modes

76 Introduction Theory Experiment Prospects Conclusion W Decay Modes

77 Introduction Theory Experiment Prospects Conclusion B Meson Decays

78 Introduction Theory Experiment Prospects Conclusion Asymptotic Freedom At high energies, the strong force between quarks become weaker. This was first observed with deep inelastic scattering

79 Introduction Theory Experiment Prospects Conclusion Parton Distribution Functions The probability density for finding a particle with longitudinal momentum fraction x at energy squared scale Q 2 Includes valence quarks, sea quarks, and gluons

80 Introduction Theory Experiment Prospects Conclusion Energy Loss for Particle ID Energy loss over distance (de/dx) varies for different momentums and particles, following the Bethe-Bloch equation

81 Introduction Theory Experiment Prospects Conclusion Bethe-Bloch Equation

82 Introduction Theory Experiment Prospects Conclusion Measuring Efficiency

83 Introduction Theory Experiment Prospects Conclusion SUSY Each particle has a pair particle with heavier mass and spin differing by 1/2 Seeks to additionally stabilize the Higgs (quadratically divergent), explain the stability of the proton, dark matter, etc

84 Introduction Theory Experiment Prospects Conclusion Elastic Diphoton Production Elastic: Protons remain intact, gap in µ rapidity, small p T Inelastic: Protons dissociate, smaller µ rapidity gap, bigger p T

85 Introduction Theory Experiment Prospects Conclusion BDT: B 0 (s) h+ h & Combinatorial Background

86 Introduction Theory Experiment Prospects Conclusion Decay Detection: B 0 (s) µ+ µ Strategy and Analysis: Triggers Removing background BDT to evaluate remaining muon pairs for signal BR calculation ɛ norm ɛ sig = ɛrec normɛ SEL REC norm ɛ TRIG SEL norm ɛ REC sig ɛsel REC sig ɛ TRIG SEL sig ɛ REC : Reconstruction efficiency of all final state particles in the decay, including detector acceptance ɛ SEL REC : Selection efficiency for reconstructed events ɛ TRIG SEL : Trigger efficiency for reconstructed and selected events

87 Introduction Theory Experiment Prospects Conclusion HPDs

88 Introduction Theory Experiment Prospects Conclusion HPDs