CP violation in the quark sector: What have we learned?

Transcription

1 CP violation in the quark sector: What have we learned? Patricia Burchat, Stanford University World Summit on Physics Beyond the Standard Model Galapagos Islands, June 22-25,

2 Notes for Printed Version of Presentation I delivered this presentation on June 22, 2006, at the World Summit on Physics Beyond the Standard Model in San Cristobal Island, Galapagos. I deliberately do not put much distracting text on my presentation slides. Therefore, the logic of the presentation may not be clear from this printed version. This talk is not intended to be a review of heavy-flavor physics or CP violation. For summarizing our current knowledge of results, I have relied heavily on the invaluable compilations by the Heavy Flavor Averaging Group, the CKMfitter Group, and the UTfit Group. For most decays, I include the minimum number of Standard-Model or New-Physics Feynman diagrams needed to make a pedagogical point, rather than all possible diagrams. This talk was prepared with Keynote and LaTeX Equation Editor (Mac OS X). 2

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4 Last year s World Summit on Evolution was a natural for the Galapagos. How can we compete?? Evidence for CP Violation: difference in the time evolution of matter and anti-matter. Evidence for Neutrino Mass: evolution of neutrino flavor in space and time. Evidence for Dark Energy: unexpected evolution of the expansion rate of the universe. 4

5 Back to the Skeptics Society Excerpt from Some people believe that skepticism is the rejection of new ideas, or worse, they confuse skeptic with cynic and think that skeptics are a bunch of grumpy curmudgeons unwilling to accept any claim that challenges the status quo. This is wrong. Skepticism is a provisional approach to claims. It is the application of reason to any and all ideas no sacred cows allowed. In other words, skepticism is a method, not a position. Ideally, skeptics do not go into an investigation closed to the possibility that a phenomenon might be real or that a claim might be true. When we say we are skeptical, we mean that we must see compelling evidence before we believe. 5

6 Ideas to treat with healthy skepticism... Supersymmetry: solution to the large quantum corrections to the Higgs mass. R-parity conservation in SUSY: prevents proton decay -- and provides attractive Dark Matter candidate. Cosmological Constant: solution to Dark Energy mystery? Motivation for best possible experimental investigation... 6

7 B Factories bd = B 0 bu = B bs = B s bc = B c bud = Λ b Hadron machines (Tevatron, LHC) 7

8 1, 000, 000, 000 BB pairs served... CLEO 10M BABAR 360M Belle 600M... plus 1, 000, 000, 000 cc pairs and 1, 000, 000, 000 τ + τ pairs 8

9 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 9

10 W χ 0 µ ν µ γ x ν e e e µ µ ẽ γ x e e e e Suppressed by ( m 2 ν M 2 W ) ! B(µ eee) could be of order with New Physics (e.g., MSSM). Experimental Results: B(µ eγ) < , B(µ eee) <

11 W χ 0 τ ν τ ν l x l τ τ x l l γ l γ l l l Experimental Results (BABAR and Belle): B(τ µγ) < B(τ eγ) < B(τ eee, µµµ, eµµ, µee) < (1 3)

12 B d, u W b t d, s l l K, K, Kπ,... d, u B b q χ 0 d, s l l 12

13 Keeping track of it all... Review of Particle Physics Heavy Flavor Averaging Group CLEO Belle BABAR Charmless B Branching Fractions CDF PDG2004 New Avg. HFAG April Branching Ratio x CKMfitter Group (primarily frequentist) UTfit Group (primarily Bayesian) 13

14 ! HFAG April 2006 CLEO Belle BABAR PDG2004 New Avg Branching Ratio x 10 6 CLEO Belle BABAR PDG2004 New Avg. B X s HFAG April Branching Ratio x

15 b sγ BaBar 05 Cleo 01 Belle 04 Neubert 04 Buras et al b " s! Branching Fraction -4 x 10 BaBar 05 Belle 04 Ali 02 Zhong 02 B * + - K lkl l + l B + - Kl lkl + l! Branching Fraction -5 15

16 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 16

17 B 0 π + K d d B 0 π + b V ub W u s Is P (B 0 π + K ) = P (B 0 π K + )? V us u K W B 0 b d V tb t V ts s u u d K π + 17

18 B 0 π + K d d B 0 π + b V ub W u s Two diagrams with different weak phases... V us u K W b d t B 0 V tb V ts s u u d K π + 18

19 B 0 π + K d d B 0 π + b V ub W u s and different (uncalculable) strong phases. V us u K W b d t B 0 V tb V ts s u u d K π + 19

20 Direct CP Violation Entries/2MeV/c K! "! Belle Entries/2MeV/c K! "! M bc (GeV/c 2 ) M bc (GeV/c 2 ) World Average: Γ(B 0 π + K ) Γ(B 0 π K + ) Γ(B 0 π + K ) + Γ(B 0 π K + ) = ±

21 CP Asymmetries Measured in Rare B Decays Γ(B) Γ(B) Γ(B) + Γ(B) CLEO Belle BABAR CDF PDG2004 New Avg. HFAG APRIL

22 CP Asymmetries Measured in Rare B Decays Γ(B) Γ(B) Γ(B) + Γ(B) CLEO Belle BABAR CDF PDG2004 New Avg. 0.0 HFAG APRIL

23 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 23

24 The Quark Mixing Matrix and the Unitarity Triangle d s b u c V ubv ud α V tbv td t γ V cbv cd β apply unitarity constraint to these two columns 24

25 CP Violation observed in interference between decays with and without mixing. World Average: sin 2β = 0.69 ±

26 History of Statistical Uncertainty on sin2β in BABAR Statistical error on first measurement (2000) Expected reduction in statistical error due to increase in data sample size: 1 N(BB) 26

27 History of Statistical Uncertainty on sin2β in BABAR 27

28 The angle α: B ππ: large penguin contributions; many ambiguities. B ρπ: use interference in Dalitz plot. B ρρ: small penguin contributions; longitudinal polarization dominates. α = ( ) α = ( ) 28

29 The angle γ from B + D ( ) K ( )+ : Depends on r B A(B+ D 0( ) K + ). A(B + D 0( ) K + GLW: B D CP K ADS: B D K ± π ±K GGSZ: B D K 0 s π + π K; Dalitz analysis measure γ and r B. D K 0 s π + π 29

30 CKM Fit: Angles Only 30

31 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 31

32 Modes that are sensitive to new physics through loops: W B 0 Entries / GeV/c b d Belle t B 0 η K 0 s M bc (GeV/c 2 ) s s s d φ, η,... K 0 S,L Entries / 1.5 ps Asymmetry B 0! "#K 0 Belle q=+1 q=$ % f &t(ps) 32

33 Difference between asymmetry from tree and loop diagrams: 2.5 σ(stat). But each loop mode has (different) additional sub-dominant diagrams, which brings in theoretical uncertainties... Average (loop diagrams) 0.50 ± 0.06 CP - violating Asymmetry 33

34 Theoretical Predictions -- QCD Factorization [Beneke, hep-ph/ colors 2 ways to estimate theory errors] Beneke [Cheng,Chua,Son i, hepph/ ] Δsin2β Cheng, Chua, Soni sin 2β eff sin 2β 34

35 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 35

36 B 0, b t W µ + Z B 0 s d, s W µ Standard Model prediction: B(B s µ + µ ) = (3.35 ± 0.32) 10 9 B 0, b t H h 0, A 0, H 0 µ + B 0 s d, s W µ 36

37 Upper Limits on Branching Fractions in Units of 10 7 B 0 µ + µ B s µ + µ BABAR Belle CDF D0 CDF LHCb: 30 B s µ + µ events per year for expected SM branching fraction of

38 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 38

39 CDF: m s = ( ± 0.07) ps 1!ln(likelihood) World average (prel.) combined data (from measured A) expectation for!m s =" (A=0) expectation for signal at!m s (A=1) !m s (ps -1 ) m s measured to 2% precision ( m s /Γ 25). c.f., m d measured to 1% precision ( m d /Γ 0.8). 39

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41 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 41

42 B τ ν τ now observed Events / 0.1 GeV signal Belle World average: B(B τ ν τ ) = ( ) 10 5 CKM fit + LQCD: B(B τ ν τ ) = (9.6 ± 1.5) 10 5 E ECL (GeV) 42

43 Theoretical Input Uncertainties on all non-angle CKM measurements now dominated by theoretical uncertainties from non-perturbative parameters (e.g., decay constants and bag parameters). Lattice QCD Staggered fermion technique plus 4th-root of determinant technique looks promising for reducing light quark masses to their physical values. Two new related methods, domain wall fermions and overlap fermions, promising but in infancy. 43

44 B τ ν τ and m d both depend on f B. Therefore, constraints are correlated. Lattice QCD with staggered fermions 44

45 Outline Radiative decays Direct CP violation The angles α, β, γ CP violation in b sss decays with loops B (s) µ + µ Two recent results: 1. Observation of B s mixing 2. Observation of B τν Putting it all together. 45

46 V ub V cb ɛ K m d m d m s sin(2β + γ) sin 2β cos 2β B ρ/ω γ B K γ angle α angle γ K πνν B τν τ 46

47 versus Treedominated Loopdominated 47

48 Violating versus CP- CP- Conserving 48

49 Theory-free (only angles) versus QCD-based (no angles) 49

50 The Future 1. B Factories: 1 billion BB pairs recorded now (not all analyzed yet). 4 billion BB pairs expected by end of factor of 2 improvement in statistical uncertainties + new analyses. Belle recorded 2 fb 1 in a three-day engineering run at the Υ(5S) and may return to this energy in the future. [Sample result: B(B s γγ) < ] 2. Hadron machines: Tevatron, LHCb, ATLAS, CMS B s mixing ( m s, Γ s, β s ), radiative decays and leptonic decays of B and B s, CKM angle γ from B and B s decays,... 50

51 Now Expected in

52 CP violation in the quark sector: What have we learned? γ α β 52

53 Polar Coordinates VIII by Frank Stella Bayesian Reality, by the UTfit group Sinjerli Variation by Frank Stella Frequentist Reality by the CKMfitter Group 53

54 What have we really learned? The B Factories and hadron machines are providing enormous data samples that allow us to explore the heavy-flavor sector with unprecedented precision. Many new analysis techniques have been developed to allow us to probe more and more decays that are potentially sensitive to new physics. If NEW PHYSICS is out there, then it must have a very special flavor and CP structure to evade all the existing searches. Continue to confront new theoretical ideas and hints of discrepancies in experimental results with healthy skepticism. 54