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CP violation studies at B A B AR

CP violation studies at B A B AR. Philip Clark. University of Colorado. Talk overview. Introduction to CP violation. PEPII and the B A B AR experiment . The charmonium system. Various  c results. B A B AR CP violation results. Summary. The Standard Model.

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CP violation studies at B A B AR

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  1. CP violation studies at BABAR Philip Clark University of Colorado

  2. Talk overview Introduction to CP violation PEPII and the BABAR experiment The charmonium system Various c results BABARCP violation results Summary CP violation studies at BaBar

  3. The Standard Model Two types of fundamental particle: Gravitational, weak, EM and strong 1) fermionswhich experience the forces quarks “confined” eg. +(ud), p(uud) leptons don’t experience strong force 2) bosons which transmit the forces Four fundamental forces: CP violation studies at BaBar

  4. Symmetries and conservation laws q q y z -x x CP = -z -y B. Cahn Relation between symmetry and conservation laws Noether’s theorem Symmetries  conservation laws • C = Charge Conjugation particle  antiparticle P = Parity:x-x T = time reversal “run the film backwards” CP violation studies at BaBar

  5. C and P symmetry and the weak interaction C P C and P are violated maximally CP violation studies at BaBar

  6. CP symmetry CPLEAR 1964: Christenson, Cronin, Fitch and TurlayCP violation in the decay of neutral kaons A CP-violating process offers an absolute way of distinguishinga world of anti-matter from a world of matter Is CP, a good symmetry for all interactions including the weak interaction? Cosmology:CP violation is one of the three necessary conditions to produce aglobal excess of matter in the Universe (Andreï Sakharov, 1967) CP violation studies at BaBar

  7. Matter-antimatter asymmetry Perhaps the answer to why the Universe looks like thisnotthat??? CP violation studies at BaBar

  8. The CKM model u d cs t b Cabibbo-Kobayashi-Maskawamatrix V: W- W- d s b ® ® b d u u u c t b d Vub Vud u u Complex matrix described by 4 independent real parameters (e.g. three angles, one phase) d s b Wolfenstein parametrization: u c t 1973 : M. Kobayashi and T. Maskawa made the connectionCP violation  third generation of quarks quark doublets l  0.22 A 0.83 CP violation in the Standard Model h≠ 0 CP violation studies at BaBar

  9. The Unitarity Triangle * * * * * * Vud 0 Vub 0 1 Vus Vud Vud 0 Vud 1 Vcd Vtd 0 Vub Vus Vcd Vtd = = * * * * * * 0 Vus 0 Vcs Vts Vcb 1 0 Vcb 0 Vts Vcd Vus Vcs Vcd Vcs Vcs 1 * * * * * * Vub Vtb Vub Vtb 1 0 0 Vcb Vtb Vtd Vcb 1 0 Vtd Vts 0 Vtb Vts  Vud Vub+ Vcd Vcb + Vtd Vtb= 0 * * * CP Violation area of the Triangle The CKM Matrix is complex and unitary 9 unitarity relations The Rescaled Unitarity Triangle The Unitarity Triangle Experimentally: constraints on the coordinates of the apex of the Rescaled Trianglein the complex plane CP violation studies at BaBar

  10. Precision test of the CKM model CP violation in the kaon system Measurements of |Vub|(b → u transitions) B0 and Bs mixing frequencies Main experimental constraints on the apex of the UT BABAR Phys. Rev. Lett. 89 (2002) 201802 World average(BABAR+Belle+…) Heavy Flavor Averaging Group 2003 CP violation studies at BaBar

  11. Is the CKM mechanism sufficient? CP violation in the quark sectoris not enough to generate the baryon asymmetry of our Universe Antimatter in the Universe? Understand the origin of CP violation in the Standard Model The Kobayashi & Maskawa mechanism can it account for all the effects of CP violation that are observed in the quark sector? and if possible, reveal inconsistencies between experimental data and theoretical predictions Possible manifestations of New Physics? Evidence for new sources of CP violation? What can we do? CP violation studies at BaBar

  12. PEP II/BABAR at SLAC Started construction in1994 Completed in 1999 Reached design luminosity in 2000 PEP II Asymmetric B Factory Luminosity records PEP-II/BABAR at SLAC design peak: best peak: total recorded: 3.0 x 1033 cm-2s-1 6.6 x 1033 cm-2s-1 130.4 fb-1 9 GeV e- on 3.1 GeV e+ CP violation studies at BaBar

  13. The BABAR detector 1.5-T Solenoid SVT DCH DIRC EMC IFR SVT CP violation studies at BaBar

  14. B Mixing Certain mesons can do a neat little trick (K0, D0, B0) A B0 meson can change into an anti B0 meson (B0) This is called “mixing”. It means these particles can (and do) oscillate into their anti-particles and back again The oscillation frequency is about 0.5 ps-1! CP violation studies at BaBar

  15. Measurement of sin2b Identify B or anti-B y z x K+ c Full reconstruction of B  cKs0 D t~ D z/cgbg 0 B tag Coherent BB production CP violation studies at BaBar

  16. Observable CP Asymmetry Dtspectrum of CP eigenstates (perfect experiment with sin2b = 0.6) Different Dt spectrum for B0 and B0 Positive and negative Dt Visible asymmetry ACP= nB0-nB0/(nB0+nB0) sin 2b CP violation studies at BaBar

  17. CP asymmetry CP violation studies at BaBar

  18. The new mode:- B0  cKs _ _ b c c c _ B0 W s K0 d d In the c analysis group we have studied B  cK and B0 cKs in the c decay modes: The two dominant modes measured have the following branching fractions BR(B0 cK0) x BR(c K0K) 36.8  11.6  6.0 x10-6 BR(B0 cK0) x BR(c K+K-0) 11.3  5.1  2.4 x10-6 Combining gives us our CP sample: CP violation studies at BaBar

  19. CP asymmetry using B→hcK CP violation studies at BaBar

  20. Sin2b per Charmonium mode Good consistency between the measurements CP violation studies at BaBar

  21. Summary of “sin2b” results 0.741 “sin2b” “reference” sin2b pure penguin mostly penguin? heavily supressed tree with competing penguin suppressed treepenguin pollution The other BABAR measurements agree with the reference sin2b Statistical conspiracy or hint of unexpected physics effect? within two standard deviations, or better but… consistently on the low side CP violation studies at BaBar

  22. The Charmonium system Other examples are the: hydrogen atom (e-p) positronium (e+e-) Discrete energy levels and splittings exist and can give information on the strong force J = 0(½ - ½ ) J = 1(½ + ½) m = 0 m = -1, 0, 1 triplet En hyperfine splitting singlet The c meson consists of a charm and anti-charm quark Bound state of two spin ½ particles (fermions) The combined angular momenta J = J1 + J2 J = |j1-j2|, |j1-j2|+1, … , (j1+j2)-1 , (j1+j2 ) and m =m1+m2 gives: the singlet state the triplet state CP violation studies at BaBar

  23. Striking similarity positronium (e+e-) charmonium (cc) triplet J/(2S) triplet singlet triplet J/triplet csinglet singlet “Introduction to High Energy Physics” D. Perkins 4th edition April 2000 Missing singlet state c(2S) CP violation studies at BaBar

  24. hc at BABAR hc mass and total width mass and total decay width hc width hc mass photon-photon production hc(2S) mass and total width ? CP violation studies at BaBar

  25. Charming, but strange mesons Ds+= cs Ds-= cs mass = 1968.5 MeV D+s D+ D+sJ(2317) D+s0 CP violation studies at BaBar

  26. Large amount of theoretical interest 32 new preprints CP violation studies at BaBar

  27. Summary What we have covered: • Prequisites • The Standard Model • The discrete symmetries C P and T • C and P violated maximally in weak interation • CP violation in the kaon system • Cosmological implications • Formalism • The Standard Model mechanism for CP violation • Testing the unitarity of the CKM matrix • Measurement of Sin2 • General methodology • Manifestation of CP violation by BaBar • Comparison to other measurements • Charmonium • B  c K transitions and branching fractions • Using the c to measure sin2 • Charmonium system and measurement of c(2S) • New particle • DsJ+ resonance CP violation studies at BaBar

  28. The hc and the Charmonium System to hadrons through virtual photon radiative : fundamental scalar state of the charmonium system, hyperfine partner of the In the c group we are studying the following decay modes: CP violation studies at BaBar

  29. Resonant structure • resonant structure • c  a0(980) ? • Should look for c  () c  (KsK) resonant structure M(K± p±) • Branching fraction large 4.9 ± 1.8 % (c  ) • 1.28% ( , ±±) cf. 1.26% (c  KsK± ±) hc Dalitz analysis and M(K0sp±) No result from Belle CP violation studies at BaBar

  30. B physics at hadron machines Geant3 LHCb event display What next? Advantages: LHC cross-section 500 mb 1012 bb pairs/year at 2x1032 cm-2s-1 (down by 5 at Tevatron ) Challenges: Event complexity Triggering Bunch spacing: 25 ns (LHC) 132 ns (Tevatron) CP violation studies at BaBar

  31. Comparison of yield and purity CP violation studies at BaBar

  32. At 1036 SLAC-PUB-8970 CP violation studies at BaBar

  33. Mixing and Sin2b analysis procedure • Reconstruct one B fully in CP eigenstate or flavour eigenstate • Other B partially reconstructed and flavour tagged • Measure D z • Fit for D t~ D z/cgbg B Mixing:- PDF(Dt) exp(–|Dt|/tB) ( 1 ± (1-2w)cos(DmDt) )R(Dt) CP violation:- PDF(Dt) exp(–|Dt|/tB) ( 1 ± (1-2w)sin2b sin(DmDt) ) R(Dt) (1-2w) is the “dilution” due to mistag R(Dt) is the vertex resolution function CP violation studies at BaBar

  34. Silicon Vertex Tracker (SVT) 580 mm • Five layer double-sided Si • Very low mass • Stand-alone tracking device for PT < 120 MeV/c • Radiation hard • z-resolution of 70m on CP vertex CP violation studies at BaBar

  35. Drift Chamber Tracking resolution CP violation studies at BaBar

  36. Detector of Internally Reflected Cherenkov Light (DIRC): Qc resolution: cosQc=1/nb CP violation studies at BaBar

  37. Cherenkov angles for p and K from D* D0p+, D0 K-p+ p K CP violation studies at BaBar

  38. Electromagnetic calorimeter CP violation studies at BaBar

  39. Time-Dependent Asymmetries Mixing using the Bflav sample: CP-violating asymmetry using the BCP sample for example Use the large statisticsBflavdata sample to determine the mis-tagging probabilities and the parameters of the time-resolution function CP violation studies at BaBar

  40. Instrumented Flux Return (IFR) ID efficiency andfake rate Barrel section of IFR Large solid angle coverage for muon id (P>1 GeV/c) and to detect neutral hadrons (K0L ) CP violation studies at BaBar

  41. Speaking of Direct CP violation … Uncertainty ~5%! CP violation studies at BaBar

  42. Separating Signal from Background (II) qq e+ e- e+ e- Signal B Other B • The other powerful thing we can do is to exploit the “event shape” • In the CM, the decay products of the B are distributed roughly spherically. This is because the pair of B mesons weigh only slightly less than the . They are essentially produced at rest • The continuum is light quark pair production, so there is lots of extra energy. All the decay products bunch into “jets” • We define variables that measure the degree of “jettiness” of the decay to tell us how more or less likely it is to be signal or background CP violation studies at BaBar

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