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A Elephant’s View of the Matter Antimatter Asymmetry of the Universe

A Elephant’s View of the Matter Antimatter Asymmetry of the Universe. n Introduction to the problem n BaBar Experiment n Measuring CP Violation n Summary & Conclusions. The “ B B-bar” Detector @ SLAC (also name of the collaboration). The Early Universe was busy place!.

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A Elephant’s View of the Matter Antimatter Asymmetry of the Universe

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  1. A Elephant’s View of the Matter Antimatter Asymmetry of the Universe nIntroduction to the problem n BaBar Experiment n Measuring CP Violation n Summary & Conclusions The “B B-bar” Detector @ SLAC (also name of the collaboration)

  2. The Early Universe was busy place!

  3. The Early Universe had lots of matter and anti-matter…. We all know about matter since it is the stuff we are made of. But what is anti-matter? Einstein (1905) Matter and energy are equivalent and can transform into each other. Dirac (1928) Invents relativistic quantum mechanics Has extra solution and predicts anti-matter Anti-matter is like matter but opposite electric charge e.g. a negatively charged proton… Ideas of Einstein and Dirac lead to lots of possibilities for anti-matter! Why not an anti-electron (= positron =e+)?

  4. Anti-Matter Found! The positron (e+) was discovered in 1932 in cosmic rays by Carl Anderson at Caltech The photograph shows how positrons were first identified in cosmic rays using a cloud chamber, magnetic field and lead plate C.D. Anderson, Phys. Rev. 43, 491 (1933). e+ bending in B-field g Why not a photon converting into matter + anti-matter? e- e- e+ A bubble chamber photo showing examples of γ→e+e- g Anti-proton found in 1955… e- e+

  5. Matter-AntiMatter Symmetry In our current view of nature the fundamental building blocks are quarks and leptons: An electron is a lepton and a proton is a bound state of 3 quarks (2 u’s and a d) There is symmetry between building blocks: For every type of quark/lepton there is an anti-quark/anti-lepton anti-proton = uud Bound states of quark anti-quark pairs are MESONS lots of mesons are possible: π+= ud, K+=us, B+=ub Anti-matter is routinely produced on Earth! Accelerator laboratories: Fermilab: anti-protons Cornell/SLAC/KEK: e+ 3 generations of quarks & leptons Hospitals: Positron Emission Tomography Looks good on Earth, what about rest of the universe?

  6. Anti-Matter in the Universe When we look into the night sky we only see MATTER! Anti-proton/proton ratio~10-4 in cosmic rays No evidence for annihilation, e+e-→γ, from intergalactic clouds In the Big Bang particle-antiparticle pairs were created from pure energy in a spontaneous explosion BUT today we cannot detect significant amounts of antimatter in the universe - why not? Since matter and antimatter can annihilate into photons how did an amount of matter survive? Predict: nMatter/nPhoton~ 0 Experiment: nb/ng~ (6.1 ±0.3) x 10-10 (WilkinsonMicrowaveAnisotropyProbe)

  7. How Can This Happen? In 1967 Sakharov showed that the generation of the net baryon number in the universe requires: • Baryon number violation(Proton Decay) • Thermal non-equilibrium • C and CP violation(Asymmetry between particle and anti-particle)

  8. C and P Symmetry Continuous symmetries have been key in our understanding and discovery of the laws of nature: WikipediA: “Noether’s theorem is a central result in theoretical physics that shows that conservation laws can be derived from any continuous symmetry.” Discrete Symmetries are important also: Parity: (x, y, z) ↔ (-x, -y, -y) vectors (mom.) change sign but axial vectors (ang. mom.) do not Charge Conjugation: particles turn into anti-particles (and visa versa) proton ↔ anti-proton, electron ↔ positron C and P are good (conserved) symmetries for EM and the nuclear force. So, they must be good for all the forces……right?

  9. P and CP Violation WRONG Parity is violated by Weak Interaction (e.g. b-decay) Discovered in 1957 (Wu, Co60) Big effect, maximal violation! Even though Parity was violated it was thought that the combination of Parity & Charge Conjugation would be conserved in Weak Interaction. C. S. Wu 1964 Cronin and Fitch discovered the violation of CP in the decay of the long-lived, CP-odd neutral K meson into a CP-even final state: Br(KL→π+π-) ~ 0.2% instead of zero. The laws of physics are different for matter and anti-matter! Cronin Fitch For ~ 40 years the only way to study CP violation was to use KAONS We now can study CP violation with B-MESONS

  10. CP Violation in the Standard Model In the SM a quark turns into another quark by coupling to a W-boson e.g. a neutron (udd) decays to proton (uud) via: d→uW- Under a CP Operation we have: coupling q’ q’ g g* CP( ) = q q W- W+ Mirror To incorporate CP violation: g ≠ g*(coupling has to be complex) It turns out that with 3 generations of quarks we can easily incorporate CP violation into the Standard Model: The Cabibbo-Kobayashi-Maskawa Matrix (1973)

  11. The Cabibbo-Kobayashi-Maskawa Matrix • The weak interaction can change the favor of quarks and leptons • Quarks couple across generation boundaries • Flavor eigenstates are not the weak eigenstates • The CKM Matrix rotates the quarks from one basis to the other Vcb Vub

  12. Visualizing CKM information from B-meson decaysThe Unitarity Triangle d s b u Vud Vus Vub Vcd Vcs Vcb Vtd Vts Vtb The CKM matrix Vij is unitary with 4 independent fundamental parameters Unitarity constraint from 1st and 3rd columns: i V*i3Vi1=0 To test the Standard Model: Measure angles, sides in as many ways possible Area of triangle proportional to amount of CP violation c t CKM phases (in Wolfenstein convention)

  13. The Standard Model predicts that, if CP violation occurs, it must occur through specific kinds of quantum interference effects. In the SM, CP violation is traced to a single parameter that is connected with how quarks acquire their masses. How are CP violating asymmetries produced? source

  14. Need two amplitudes Need a CP violating phase (f) Need a CP conserving phase (d) How are CP violating asymmetries produced? |A| ¹ |A | A=A1+A2 A=A1+A2 f f d

  15. The Three Types of CP Violation in SM I) Indirect CP violation/CP violation in mixing K®pp, K®pln, expected to be small (SM: 10-3) for B0’s II) Direct CP violation: Prob(B®f) ¹ Prob(B®f) e¢/e in K®pp (tiny…(1.66±0.26)x10-3) Br(B0®K-p+) ¹ Br(B0®K+p-) III) Interference of mixing & decay: Prob(B(t)®fCP) ¹ Prob(B(t)®fCP) B0®yKs (CKM angle b) B0®p+p- (CKM angle a) Only CPV possible for charged B’s Due to quantum numbers of Y(4S) and B meson we must measure time dependant quantities to see this CP violation In this talk I will be discussing type II & III CP violation

  16. Getting the Data Sample Use e+e- annihilations at Y(4S) to get a clean sample of B mesons • At Y(4S) produce B-/B+ (bu/bu) and B0B0 (bd/bd) mesons • mB0 ~ mB- ~ 5.28 GeV (about 5X the mass of a proton) The Y(4S) - a copious, clean source of B meson pairs 1 of every 4 hadronic (e+e-→qq) events is a BB pair No other particles produced in Y(4S) decay, just the B-mesons Produce equal amounts of matter and anti-matter bound states of bb quarks e+e-→qq BB Threshold center of mass energy (GeV/c2)

  17. PEPII-Asymmetric e+e- Collider PEPII is an asymmetric e+e− collider: 9 GeV (e-)/3.1 GeV (e+) A B-meson travels a measurable distance before decay: bg=0.56 → <bgct>~260mm Stanford Linear Accelerator Center, Stanford, California

  18. Data Collection at PEPII To get the data set necessary to measure CP-violation with B’s we need a B-factory SLAC and KEK Both factories have attained unprecedented high luminosities: >1034/cm/s2 BABAR has collected > 400 fb-1 (BABAR + Belle > 1000 fb-1) Note: 1fb-1 ~ 1.1 million BB pairs BaBar will soon have 1 billion B-mesons

  19. The BABAR Detector 1.5 T Solenoid Electromagnetic Calorimeter (EMC) Detector of Internally Recflected Cherenkov Light (DIRC) e+ (3.1 GeV) e- (9 GeV) Drift Chamber (DCH) Instrumented Flux Return (IFR) Silicon Vertex Tracker (SVT) BaBar detector features: Charged particle tracking (silicon+drift chambers+1.5T Bfield) Electromagnetic calorimetry (CsI) ®g and electron ID p/K/p separation up to the kinematic limit (dE/dx+DIRC) Muon/KL identification BaBar collaboration: 11countries 80 institutions ~600 physicists

  20. background subtracted First Observation of Direct CPV with B’s Study the decay rate of B0→K+π- Vs B0→K-π+ PRL 93, 131801 (2004) Actually, this isn’t so exciting. It is hard to relate direct CPV to the CKM parameters!

  21. q/p mixing CPV due to Mixing & Decay at the Y(4S) CPV from the interference between two decay paths: with and without mixing Measure time dependent decay rates & Dm from B0B0 mixing |BL>=p|B0>+q|B0> |BH>=p|B0>- q|B0> Direct CP Violation: C¹ 0 |Af/Af|≠1→ direct CP violation |q/p|≠1→ CP violation in mixing Sf and Cf depend on CKM angles

  22. Complications from Quantum Mechanics Quantum Mechanics plays a cruel trick at the Y(4S). Because of the QN’s of the Y(4S) (JPC=1--) and the B0 meson (JP=1-) the time integrated asymmetry is ZERO. Simply counting the number (N) of B-meson decays won’t work. Must measure the decay rates as a function of time. However, if the Y(4S) is produced at rest the B’s don’t travel far enough to measure their decay times: Average decay length of a B-meson in Y(4S) rest frame is: <L>=bgct=(p/m)ct=(0.3/5.3)(459mm)=26mm This is too small to measure with today’s technology. Solution: Build accelerator where the Y(4S) is moving! At PEPII bg of Y(4S)=0.56 and <L>=260 mm

  23. t =0 Dz = Dt gbc bg =0.56 l - (e-, m -) The two mesons oscillate coherently : at any given time, if one is a B0 the other is necessarily a B0 In this example, the tag-side meson decays first. It decays semi-leptonically and the charge of the lepton gives the flavour of the tag-side meson : l -= B 0l+ = B 0. Kaon tags also used. (4S) How to Measure Time Dependent Decay Rates At t=0 we know this meson is B0 We need to know the flavor of the B at a reference t=0. B 0 rec B 0 B 0 tag Dt picoseconds later, the B 0 (or perhaps it is now a B 0) decays.

  24. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g (0,0) (0,1) The CKM Unitarity Triangle b

  25. The Many Ways to Measure CKM angle b Can use 3 different categories of B0 decays to measure b: golden mode But, for technical reasons these decays are not very useful…

  26. Precise Measurement of sin2b from B0®charmonium K0 CP even CP odd Theoretically very clean: ACP(t)=Sfsin(DmDt)-Cfcos(DmDt) The dominant penguin amplitude (suppressed by ~25) has same phase as tree SM prediction: Cf=0 Þ ACP(t)=Sfsin(DmDt) recent model-independent analyses [e.g. PRL 95 221804 (2005)] DS=0.000±0.012 decay B0 mixing K0 mixing Experimentally very clean: Many accessible decay modes with (relatively) large BFs B→ψK0~8.5x10-4 B→ψ(2S)K0~6.2x10-4 B→χc1K0~4x10-4 B→ηcK0~1.2x10-3

  27. Precise Measurement of sin2b from B0®charmonium K0 ACP(Dt) = -ηfsin2bsin(DmdDt) Results from ICHEP 2006 hep-ex/0607107 348x106 BB sin2b=0.710±0.034±0.019

  28. · · 1s CKM fit 2s Brief History of sin2b from B0charmonium K0 Pre-ICHEP 2006 ICHEP 2006 Great success for Standard Model Great success for all of us: theorists, experimentalists, accelerator physicists ICHEP 2006

  29. SM Sin2beff in b→s Penguins • Decays dominated by gluonic penguin diagrams • Golden example: B0→fKS • No tree level contributions: theoretically clean • SM predicts: ACP(t) = sin2bsin(Dmt) NP • Impact of New Physics could be significant • New particles could participate in the loop → new CPV phases • φK0 • η′ KS, η′ KL • KS KS KS • KSπ0 • K+K−KS, K+K−KL • ω KS • f0(980) KS • Measure ACP in as many b→sqq • penguins as possible!

  30. Hunting for new physics: CPV + b→s Penguins • Complications: • Low branching fractions (BF) • Experimentally challenging: • detached vertices • Non-penguin processes can pollute: sin2beff-sin2b Use theory to estimate deviation from sin2b SM corrections to naïve model: QCD factorization: 2-bod: [Beneke; PL B620, 143 (2005)] 3-body: [Cheng,Chua,Soni; PRD72, 094003 (2005)] SU(3) based model independent bounds Use measured BFs & parameters in models Dsin2b

  31. Example: Analysis of B0→h¢K0 347  106 BB pairs Þ ~1100signal events B0→h¢Ks B0→h¢KL hCP=−1 hCP=+1 h¢(h(gg)p+p−)KS & Ks→p+p-/p0p0 h¢(rg)KS & Ks→p+p-/p0p0 h¢(h(3p)p+p−)Ks & Ks→p+p- h¢(h(gg)p+p−)KL 4.9s from zero

  32. BABAR Summary of CPV + b → s Penguins no evidence for direct CPV Individual modes are consistent with the charmonium value BUT the naïve b®s average is still lower by ~2s compared with charmonium sin2b value (recall theory said it should be larger than charmonium) sin2beff-sin2b Dsin2b

  33. All “sin2b” Results Compared Naïve average of all bgs modes: sin2beff = 0.52 ± 0.05 penguin & tree differ by 2.6 s Hazumi ICHEP06 bgs modes smaller than bgccs in all 9 modes

  34. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g (0,0) (0,1) The CKM Unitarity Triangle b [21.2 ± 1.3]o

  35. * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb What About the Other Angles? (r,h) b a g (0,0) (0,1) [21.2 ± 1.3]o

  36. Tree decay B0B0mixing Penguin decay  Measuring the CKM angle a In an ideal world we could access a from the interference of a b→u decay (g) with B0B0 mixing (b): g Penguin/Tree~30% But we do not live in the ideal world.. There are penguins… and penguin pollution

  37. BABAR Combined Constraints on a Extraction of a depends crucially on penguin contributions Must combine many measurements for precise determination B→r0r0/r+r0/r+r- B→p0p0/p+p0/p+p- B→(rp)0 Theory Ûexperimental feedback is essential rr gives 3 windows rp chooses the window (~p/2) pp fine tunes position in window

  38. (r,h) * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g b (0,0) (0,1) The CKM Unitarity Triangle [93 ± 11]o a [21.2 ± 1.3]o

  39. Measuring the CKM angle g Use interference between different B decays that access the same final state. Example: B+→D0K+with D0→K-π+ & B+→D0K+with D0→K-π+ Can also use D0/D0 decays to CP eigentates (π+π-, K+K-, Ksπ0…) ADS method → K-p + → K-p + Color favored b→c amplitude Ä Cabibbo suppressed u→s amplitude Color suppressed b→u amplitude Ä Cabibbo favored c→s amplitude JOnly tree diagrams: 100% Standard Model JNo need for time dependent analysis LLDecay rates are very small (<1 in 10-7 B decays)

  40. BABAR Combined Constraints on g

  41. * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb The CKM Unitarity Triangle (r,h) [93 ± 11]o g a b [62± 31]o (0,0) (0,1) [21.2 ± 1.3]o

  42. CKMfitter Inputs: Putting All CKM Measurements Together a+b+g= (93±11)º+ (21±1)º+ (62±31)º = (176±31)º As of today the complex phase in the CKM matrix correctly describes CP Violation in the K & B meson systems! ¿ Much more to come from BaBar/Belle, CDF/D0, and LHCb Super B-factories in Japan & Italy?? Will they find CKM violation????

  43. In spite of all we have learned about CP Violation the origin of the cosmological matter antimatter asymmetry still remains a mystery. Must go beyond the Standard Model

  44. Extra Slides

  45. Expected precision Vs Lum. sin2b in penguins Luminosity (ab-1) Summary and Outlook: b BABAR & Belle measure sin2b in ccK0 modes to 5% precision sin2bcharmonium=0.674±0.026 (HFAG) Comparison with sin2beff in bs penguins could reveal new physics sin2beff = 0.52 ± 0.05 Need to carefully evaluate SM contributions sin2beff measurements are statistically limited but we can add new modes & beat 1/√L scaling Þr0Ks, p0p0Ks

  46. h0 h0 h0=p0,h, h’,w Resolving the sin(2b) Ambiguity sin(2b) is the same for b, p/2-b, p+b, 3p/2-b Several methods available to resolve the ambiguity Can resolve ambiguity with a time-dependent analysis of D0→Ksπ+π- Usebcud decays: B0D(*)0h0 with D0DCPKsπ+π- [A.Bondar, T.Gershon, P.Krokovny, PL B624 1 (2005)] The Dalitz plot model is taken from a sample of D*D0π+ decays, D0Ksπ+π- Use CLEO isobar formalism for the D0 decay amplitude (PRD 63,092001 (2001), PRL 89, 251802 (2002), erratum: 90,059901 (2003)) Theoretically clean (no penguins), Neglect DCS B0DCPh0 decay Interference of Dalitz amplitudes sensitive to cos2b

  47. The CKM Triangle & New Physics circa 1990! Nir and Quinn

  48. Key Analysis Techniques Threshold kinematics: we know the initial energy of the Y(4S) system Therefore we know the energy and magnitude of momentum of each B-meson • Event topology Signal Signal (spherical) Background Background (jet-structure) Most analyses use an unbinned maximum likelihood fit to extract parameters of interest

  49. h0 h0 h0=p0,h, h’,w Resolving the sin(2b) Ambiguity sin(2b) is the same for b, p/2-b, p+b, 3p/2-b Resolve ambiguity: usebcud decays: B0D(*)0h0 & D0DCPKsπ+π- [A.Bondar, T.Gershon, P.Krokovny, PL B624 1 (2005)] Interference of amplitudes sensitive to cos2b. Study shows that data favors b=220 over 680 at 87% CL Other Methods to resolve ambiguity: Time dependent analysis of B0D*+D*-Ks cos2b>0 at 94% CL (hep-ex/0608016) model dependent analysis: PRD 61, 054009 (2000) Extract cos2b from interference of CP-even and CP-odd in states (L=0,1,2) in time-dependent transversity analysis of B0J/yK*0(K*0Ksp0), PRD 71, 032005 (2005) cos2b<0 excluded at 86% C.L.

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