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Guillaume Thérin LPNHE – Paris Lausanne

Measurements of g. BaBar. with. detector at SLAC. Guillaume Thérin LPNHE – Paris Lausanne. Outline. Theoretical context CP violation Standard model PEPII and BaBar B-Factory Direct measurements of g B -  D ( * ) K ( * )- method (ADS, GLW, GGSZ) Direct measurements of sin(2 b+g )

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Guillaume Thérin LPNHE – Paris Lausanne

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  1. Measurements of g BaBar with detector at SLAC Guillaume Thérin LPNHE – Paris Lausanne Lausanne – g measurements with

  2. Outline • Theoretical context • CP violation • Standard model • PEPII and BaBar B-Factory • Direct measurements of g • B- D(*)K(*)- method (ADS, GLW, GGSZ) • Direct measurements of sin(2b+g) • B0 D(*)-p+, D(*)-r+, • B0 D(*)0K(*)0 • Combinations of the results with CKMFitter Lausanne – g measurements with

  3. Theoretical context Lausanne – g measurements with

  4. CP violation in the Standard Model • The CKM matrix elements Vij describe the electroweak coupling strength of the W to quarks • The CKM mechanism introduces quarkflavour mixing Complex phases in Vij are the origin of SMCP violation CP = The phase changes signunder CP. Transition amplitude violates CP if Vub ≠ Vub*, i.e. if Vub has a non-zero phase Lausanne – g measurements with

  5. * VtdVtb * VudVub * * VcdVcb VcdVcb Structure of the CKM matrix • Mixing is weak  Magnitude of elements strongly ranked (leading to ~diagonal form) 3 particle generations and unitary CKM matrix: 4 parameters (3 real + 1 im.) Wolfenstein : (r, h) a/f2 b/f1 g/f3 (0, 0) (0, 1) Unitarity Triangle 3 real par. A, λ (= sin qCabibbo = 0.22) and ρ 1 imaginary par. iη (responsable of CP violation) g= arg( V*ub/ Vcb ) (Wolf.) • Measuring SM CP violation  Measure complex phase of CKM elements Lausanne – g measurements with

  6. Experimental Constraints on the Unitarity Triangle Before the B-factories, constraints came from kaons, B oscillations and |Vub/Vcb| B-factories can be used to over-constrain the triangle and so to test the SM CP violation studies established: • sin(2b) = 0.685 ± 0.032 charmonium • experimental contraints on a • g (this talk) harder to measure • The SM test consists of comparing 2 kinds of measurements : • gP (new physics) • B decays in charmless 2-bodies (envolving amplitudes with penguins) • gst(Standard Model), • B- D(*)K(*)- (GLW, ADS, GGSZ) • B0 D(*)p, D0K(*)0 (g or sin(2b+g)) • Bs Ds K(*)0 (probably at LHC) http://ckmfitter.in2p3.fr bcus,bucs bcud,bucd bcus,bucs Lausanne – g measurements with

  7. PEPII / BaBar, Experimental apparatus Lausanne – g measurements with

  8. The PEP-II B factory - Specifications 9 GeV 3.1 GeV • Produces B0B0 and B+B- pairs via Y(4s) resonance (10.58 GeV) • Asymmetric beam energies • Low energy beam 3.1 GeV • High energy beam 9.0 GeV • Clean environment ~28% of all hadronic interactions are BB (4S) BB threshold Lausanne – g measurements with

  9. The PEP-II B factory - Performance Trickle injection: w/o trickle injection top-off every 30-40 min RUN5 continuous filling with trickle injection more stable machine, +35% more lumi RUN4 Records: • PEP-II top lumi: 1.x1034 cm-2s-1 (~10 BB pairs per second) • Integrated luminosity • PEP-II delivered: 311 fb-1 • BaBar recorded: 299 fb-1 on-peak+off-peak data • Most analyses use 211fb-1 of on-peak data RUN3 Most analyses are based on 232.106 BB pairs RUN2 RUN1 Lausanne – g measurements with

  10. The BaBar detector Silicon Vertex Tracker : 5 layers of double-sided Silicium, vertexresolution of 60-120 mm BABAR Collaboration : 11 countries and ~590 physicists ! Support tube Drift CHamber : 40 layers s(pT)/pT = (0.13 pTÅ 0.45)% Detector of Internally Reflected Cherenkov light : 144 quartz bars, 11000 PMs K/p > 2.5s (p < 4.3 GeV/c) ElectroMagnetic Calorimeter : 6580 CsI crystals (Tl) s(E)/E = (2.32 E–1/4Å 1.85)% Solenoid :1.5T Instrumented Flux Return : iron / RPCs [ → LSTs ] Lausanne – g measurements with

  11. > ~ Selecting B events for CP analysis B mesons identification e+ (3.1 GeV) mES DE E*beam very well known e- (9 GeV) E*beam = E*Υ(4S) / 2 E*beam 2 mB Combinatorial e+e- qq bkg suppression K/p separation with Cherenkov angle Signal e+e- → bb Excellent separation between 1.5 and 4 GeV/c b isotropic udsc e+e- → uu, dd, ss, cc Jet-like -2 –1 0 1 2 3 4 Fisher discrimnant Lausanne – g measurements with

  12. Constraining g with B- D(*)K(*)- decays Introduction Gronau-London-Wyler method Atwood-Dunietz-Soni method Giri-Grossman-Soffer-Zupan method Combination Lausanne – g measurements with

  13. f f u u u u u c • Gronau-London-Wyler : CP eigenstates • Atwood-Dunietz-Soni : DCSD D0 and CA D0 ex. : B-→ (K+p-)D K- K+p- Ksp+p- Ksp0 K+K- p+p- Ksf • Giri-Grossman-Soffer-Zupan : D0→ Ksp+ p- Ksw Constraining g with B±→ D(*) K(*)± decays Favored decay b c Suppressed decay b u Vus b u s K*- D0 Vub Vcb B- b c s K*- B- D0 a rBei(d-g) a Ratio of the 2 amplitudes Strong phase CKM Angle g= arg( V*ub/ Vcb ) rB ≈ 0.1-0.2 • D0 , D0  same f interference sensitive tog : B(B- D(*)K(*)-)  5. 10-4 rD / rB ≈ 0.5 ! rB, d, different for DK*±, DK± and D*K± modes Lausanne – g measurements with

  14. Constraining g with B- D(*)K(*)- decays Introduction Atwood-Dunietz-Soni method Giri-Grossman-Soffer-Zupan method Combination Gronau-London-Wyler method Lausanne – g measurements with

  15. g A(B+→DCP K*-) g A( B-→D0K*- ) A(B- →DCP K*+) d GLW - Observables of the method - B± D(*) K±(*) Direct CP violation: N(B+ → D K*+) ≠ N(B- → D K*-) Observables are: non-CP modes ≈ flavour eigenstates Lausanne – g measurements with

  16. GLW - Characteristics of the method - B± D(*) K±(*) Theory: Extract the 3 unknowns (g, rB, d(*)B) for each modefrom 4 observables  a relation between observables: 8-fold ambiguity in g Sensitivity on g depends on rB A+ R+= - A- R- Experience: • D(*)K modes • suffer from bkg from D(*)0p (12x higher BF)  need excellent p/K separation • D(*)K* modes • cleaner but lower BF and lower efficiency • need to consider D(*)Ks p irreductible component • Need to take into account dilution effect from opposite-sign CP D0 decays in fKS0 and wKS0 (for instance D0a0KS0) • D*K* need angular analysis -not realistic with current statistics Lausanne – g measurements with

  17. mass (KS0) • distance of flight CP- : K s0 X. X = {f , p0 , w} Ks0 • mass (KS0) • distance of flight • mass (K*) • K* helicity p+ mass (f) f helicity track PIDs D0 f K*- • mass (D0) • D0 helicity Ks0 p- p- p0 mass (p0) CP+, non-CP D0 track PIDs w mass (w) w helicity dalitz angle track PIDs CP=+1 : K+K-, p+p-,non-CP : K-p+ , K-p+p0, K- 3p GLW – Reconstruction and selection - B± D K±* • 232 millions of charged B decays • Reconstructed BF of the order of 2.10-7 – 10-6 • Event Shape Variables • cos(q) of B momentum • mES & DE B- Lausanne – g measurements with

  18. CP- : 25 CP+ : 24 GLW – Distribution of the simulation and fit strategy - B± D K±* Gaussian G Signal (rB = 0) B+B- B0B0 cc uds mes Argus function A DE • Adding CP+ modes together (resp. CP- and non-CP) • Strategy : fit in one dimension in mes • Use data inDEandD0 masssidebands to fix the background shape • Hypothesis : common parameterisation for all modes (checked on MC) D0 mass mes Lausanne – g measurements with

  19. GLW - Results of the fit for 232 millions of charged B-B± D K±* PRD72,71103(2005) CP-1 non-CP CP+1 • One single Gaussian G • One single Argus A • Simultaneous fit in mes for 3 regions : • Signal • mD0 sidebands • D E sidebands B+ SIGNAL REGION B- m(D0) sidebands DE sidebands Lausanne – g measurements with

  20. GLW - Results-B± D(*) K± • Main background from kinematically similar B→D0pwhich has BF 12x larger • So the signal and this main background are fitted together • BD0K: 232M B± decays, D0KK, pp, KS0p0 • 2D fit to DE and the Cherenkov angle of the prompt track A 2s cut on qC in these plots BD*0K: 123 B± decays, only D*0D0p0, D0KK,pp at the moment: Kaon hypothesis Only CP+ modes 3D Fit(mes, DE, qC) without the kaon hypothesis Lausanne – g measurements with

  21. GLW – Summary - B± D(*) K±(*) 1 0 No asymmetry seen All values compatible with 1 except for the DK* mode  rB is bigger than expected for this mode Lausanne – g measurements with

  22. Constraining g with B- D(*)K(*)- decays Introduction Gronau-London-Wyler method Giri-Grossman-Soffer-Zupan method Combination Atwood-Dunietz-Soni method Lausanne – g measurements with

  23. d u u u s u s u u u u c u d Cabibbo suppressed cd amplitude rD = Cabibbo favoured su amplitude Sensitivity: rD / rB ≈ 0.5 rD= 0.060±0.003 • Better sensitivity than GLW but lower BF • 4-fold ambiguity in g : need to measure at least two D decay modes to loose ambiguity between g and the strong phase ADS - Method - B± D(*) K ±(*) s K*- s B- c b B- D0 D0 u b Cabibbo suppressed bu amplitude rB = Cabibbo favoured bcamplitude Lausanne – g measurements with

  24. ± B± [K±p ]D K*± ± B± [K p±]D K*± ADS – Results of the fit - B± [K p±]D K±(*) ± PRD72,71104(2005) WS B+ B+ [K-p+]D K*- WS RS ~4 events ~90 events WS B- B- [K+p-]D K*- mES (GeV/c²) Cut same variables as GLW Some of them are put in a neural network Lausanne – g measurements with

  25. GLW ADS combination GLW+ADS – Interpretation - B± D K±* PRD72,71104(2005) CkmFitter Frequentist approach to determinegandrB Construction of Confidence Level plots EPJ,C41,1 (2005) g[0,p] &(dD+d)[0,2p] (semi-log scale) 1-CL 1-CL 1s 1s 2s 2s 3s 3s g[75°,105°](excluded @2s CL) g(deg) rB Lausanne – g measurements with

  26. * ADS – Results - B± [K p±]D(*) K± ± hep-ex/0504047 0<dD<2p rD±1s 51°<g<66° B-→DK- g[0,p] * B-→D*[Dp0]K- * rB<0.23* • D*→Dp0/Dg ≠ indD*by p B-→D*[Dg]K- PRD70,091503(2004) * (r*B)²< (0.16)²* (Bayesian r*B²>0 & uniform,  g and dD*) Lausanne – g measurements with

  27. ADS – Summary - B± D(*) K±(*) No signal peak was observed More sensitive than GLW but need more statistics to constrain g Other non-CP modes to add and reduce ambiguities 0 Lausanne – g measurements with

  28. Constraining g with B- D(*)K(*)- decays Introduction Gronau-London-Wyler method Atwood-Dunietz-Soni method Combination Giri-Grossman-Soffer-Zupan method Lausanne – g measurements with

  29. GGSZ – Dalitz Method -B± D(*) K±(*) Reconstruct BD(*)0K(*) with Cabibbo-allowed D0/D0KSp+p- If D0/D0 Dalitz f(m+2,m-2) is known (included charm phase shiftdD): B-: B+: 2 Schematic view of the interference |M-|2 = gambiguity only 2-fold (g ↔ g+p) Experimentally: BF[(B  D0K)(D0K0 )]=(2.20.4)10-5  High statistic Only charged tracks in final state  high efficiency/low bkg Lausanne – g measurements with

  30. GGSZ – D0 KSp+p-Dalitz model f -B± D(*) K±(*) f(m2+,m2-) extracted from high statistics tagged D0 events (from D*) CA K*(892) D decay model described by coherent sum of Breit-Wigner amplitudes dDphase difference determined by model Not so good for pp s-wave. Need controversial s(500) and s’(1000) to reasonably describe the data Masses and widths fixed to PDG2004 values except for s and s’ (fitted) r(770) DCS K*(892) 13 fitted resonances + NR term +s+s’ c2/dof3824/3022=1.27 Lausanne – g measurements with

  31. Mode Signal events B-DK− 282 ± 20 B-D*[D0]K− 90 ± 11 B-D*[D]K− 44 ± 8 B-DK*−[K0Sp-] 42 ± 8 (mES>5.27 GeV/c²) GGSZ – Fit results -B± D(*) K±(*) hep-ex/0504039 DK- D*[D0]K- D*[D]K- B-DK*−[K0Sp-] Lausanne – g measurements with

  32. GGSZ/GLW+ADS– Confidence regions -B± D K±* More constraint with GLW/ADS for this mode than with GGSZ GLW+ADS GGSZ rB g(deg) 2sCL 1s CL 1s 1s 2s g(deg) k.rsB 0<k<1 is an extra parameter with no assumption made on (K0Sp-) under the K*- part (K0Sp-) under the K*- and Kp S-wavesaccounted for in a model where strong phase are unknown (k=1) Lausanne – g measurements with

  33. GGSZ – Combined results -B± D(*) K±(*) 7D Neyman Confidence Region: • rB(DK), rB(D*K), k.rsB • dB(DK), dB(D*K), dB(DK*) • g D0K- D*0K- D0K*- g(deg) 2sCL 1s CL rB rB k.rsB(<0.75 @ 2s CL+ and no assumption) g = 67°± 28°(stat.) ± 13°(syst. exp.) ± 11°(Dalitz model) Lausanne – g measurements with

  34. Constraining g with B- D(*)K(*)- decays Introduction Gronau-London-Wyler method Atwood-Dunietz-Soni method Giri-Grossman-Soffer-Zupan method Combination Lausanne – g measurements with

  35. GLW+ADS+GGSZ - Combination -B± D(*) K±(*) GGSZ B± D K± Sensitivity for all methods depends on rB B± D* K± GLW+ADS B± D K*± 1-CL g(deg) g = Lausanne – g measurements with

  36. Constraining sin(2b+g) with B0 D(*)p/r decays Lausanne – g measurements with

  37. p+/r+ 2b g p+/r+ A(B0 → D(*)- p+) ≈ 0.015 r(D(*)p) ≡ r(*) = A(B0 → D(*)- p+) CP violation in B0D(*)p/r • Large branching fraction for favoured decay (~3x 10-3) • Small BR for suppressed decay (~10-6) • Small CP violating amplitude Suppressed b u decay Favoured b c decay Strong phase difference CKMangle Determines the sensitivityof the method Lausanne – g measurements with

  38. < ~ 1 – r2 C = ≈ 1 l+ 1 + r2 S± ≈2r sin ( 2b+g±d ) , |S±| 0.03 K+ Time-dependent decay rate distributions - K+ -s Tag B K+ U(4s) Reco B z + Dt @Dz/gbc Dz Mixing-Decay interference ∞ ± ± ± P(B0 → D(*)p ,Dt) 1 C cos(DmdDt) + S sin(DmdDt) ± ± ∞ ± P(B0 → D(*)p ,Dt) 1 C cos(DmdDt) - S sin(DmdDt) ± ± neglecting terms in o(r2) Measurements of S+ and S- determine 2b+g and d if r is an external input Experiment : tag the flavour of the B with lepton and kaon categories combined in a neural network lepton tag kaon tag Lausanne – g measurements with

  39. ∞ K+ K+ ’ Possible CP violation on the tag side PRD68, 034010 Potential competing CP violating effects in B decays used for flavour tagging + Kaon tag : expect CP violation comparable to signal → Modified time distributions signal side tag side P(B0 → D(*) -p+ ,Dt) 1 +C cos(DmdDt) + sin(DmdDt) [± 2r sin(2b+g+d) +2r’ sin(2b+g±d’)] Kaon and other flavour tags Lepton tags Observables a, b, c Lausanne – g measurements with

  40. Signal D*r Combinatoric BB Peaking BB Continuum N(B0 tag) + N(B0 tag) N(B0 tag) - N(B0 tag) ACP= B0→D*-p+: partial reconstruction results hep-ex/0504035 Lepton Tags Find events with two pions and examine the missing mass mmiss Preliminary Preliminary kaon Tags Preliminary Lepton Tags Mean value 18710 ± 270 lepton tags 70580 ± 660 kaon tags Lausanne – g measurements with

  41. B0D(*),D full reconstruction results - Reconstruct B0 candidate using full decay tree: Lepton tags, D* final state ++0, D+K-++, Ks+ D*+ D0+, D0K-+,K-+0,K-+-+,Ks+- background Lausanne – g measurements with

  42. SU(3) r(D) = 0.019 ± 0.004 r(D*) = 0.015 ± 0.006 r(Dr) = 0.003 ± 0.006 Determination of r I. Dunietz, Phys. Lett. B 427, 179 (1998) • Simultaneous determination of sin(2+) and rfrom time-evolution is not possible with current statistics  Need r as an external input • Estimate amplitude ratios from B0Ds(*)+- using SU(3) symmetry Assuming several hypotheses for SU(3) : • Assuming factorisation • Neglect exchange and annihilation diagrams without any theoritical errors Lausanne – g measurements with

  43. Interpretation of sin(2b+g) assuming SU(3) Assign theoretical error on r(D*p), r(Dp) and r(Dr) - Combine partial and fully reco results for the a and clep parameters Bayesian approach Frequentist approach (Feldman-Cousins) 30% theoretical error on r 100% theoretical error on r 68 % CL 90 % CL 90 % 68 % www.utfit.org |sin(2+)| > 0.64 @ 68 % C.L. |sin(2+)| > 0.42 @ 90 % C.L. |2+| = 90o 43o Lausanne – g measurements with

  44. Conclusion Lausanne – g measurements with

  45. Conclusion Measuring g at B-Factories: an impossible mission a few years ago GGSZ analyses give the best results The GLW method eliminates g constraints close to 900 All analyses are statistically limited or statistics are too low for most sensitive methods • B- D(*)K(*)- (GLW, ADS, GGSZ) GLW,ADS,GGSZ WA = (63+15-12)º • B0 D(*)p/r |sin(2β+γ)| BaBar >0.64 (@ 68 %CL) Lausanne – g measurements with

  46. Backup Slides Lausanne – g measurements with

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