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measurements of V cb , branching fractions, form factors

measurements of V cb , branching fractions, form factors. E.Barberio University of Melbourne FPCP: Daegu October 2004. Semileptonic B decays. V cb. tree level, short distance:. decay properties depend directly on fundamental Standard Model parameters:

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measurements of V cb , branching fractions, form factors

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  1. measurements of Vcb, branching fractions, form factors E.Barberio University of Melbourne FPCP: Daegu October 2004

  2. Semileptonic B decays Vcb tree level, short distance: decay properties depend directly on fundamental Standard Model parameters: - |Vcb|: essential ingredient in tests of CKM unitarity - mb, mc: predictions of B decay rates, precision electroweak observables E. Barberio

  3. Extracting Vcb, mb, mc + higher order & long distance: precise determination of Vcb mb mc! quarks are inside hadrons bound by soft gluons  both perturbative (higher order QCD (asn) corrections) and non-perturbative (LQCD) long-distance interactions of b quark with light quark tools: Heavy quark symmetry and lattice QCD E. Barberio

  4. Heavy Quark Symmetry • when the energy of soft gluon LQCD~250 MeV << mb,c heavy quark • heavy quark is ‘invisible’ to gluon probes with de Broglie wavelegnth lg>>1/mc,b: • heavy quarkspin and mass (flavour) are good symmetry as (mQ/LQCD) ∞ • - departure from theheavy quarksymmetry can be expressed as (LQCD/mQ)n corrections Two methods to extract Vcb Exclusive Inclusive E. Barberio

  5. HQET and B D*ln l n - n q2 b c w=1 Vcb - n c c w>1 q q Heavy Quark Effective Theory (HQET): simplified description of processes involving heavy  heavy quark transitions non-perturbative effects described by form factors in mQ∞(1)=1 Vcb extraction with little model dependence bonus: BD(*)ln largest branching fraction of B decay modes all B D(*)ln transitions are described by one form factor (Isgur-Wise function) as a function of w: the D* boost in B rest frame q2  4-momentum transfer w=1 D* produced at rest in B rest frame E. Barberio

  6. Vcb from B D*ln DELPHI (unfolded data) F(1)Vcb w in HQET K(w): is the phase space (known function) F(w):unknown form factor=F (1)•g(w) in the heavy quark limit mQ∞F(1) =(1)=1 measure dG/dw(w) and extrapolate at w=1g(w) slope important fit for both intercept F(1)|Vcb| and slope (r2) [Caprini, Lellouch, Neubert, Nucl.Phys.B530(98)] E. Barberio

  7. B D*ln: signal and w reconstruction D*  Dp D  Kp(p) Belle l n q2 b c Vcb B  D*ln D* p+slowD0: m(D*)-m(D0)~m(p+): the p+ is almost at rest close to K(w=1) in the B rest frame p+ difficult or impossible to reconstruct if the B is produced at rest or has little boost w  pn and En: need good resolution for En+pn, easy if the B is produced at rest of with little boost E. Barberio

  8. LEP Z bb: B0 large variable momentum ~30 GeV good efficiency at w~1: less extrapolation uncertainty at w=1 B D(*)ln: signal efficiency Bd0D*+- B-D*0- CLEO w U(4S)  B0 at rest or almost large data sample, good w resolution, low D** background poor efficiency at w~1 poorer w resolution large background from higher D** E. Barberio

  9. B D(*)ln: background CLEO BD**ln with D**pD*/pD0resonant (narrow and wide) and non resonant LEP: resonant D**:different form factors depending on assumption on quark decay dynamics [Leibovich,Ligeti,Stewart,Wise] D**shape from constraints on D** rates: Br(BD*2ln )/ Br(BD1ln) <0.4 U(4S): E. Barberio

  10. B D(*)ln: form factor shape expansion around w=1 up to second order: use dispersive relations to constraint the shape Caprini,Lellouch,Neubert NP B530(98)153 and Boyd,Grinstein,Lebed PRD56(97)6895 R1,R2 calculated using QCD sum rules R1(w)1.27-0.12(w-1)+0.05(w-1)2 R2(w) 0.80+0.11(w-1)-0.06(w-1)2 measured by CLEO: R1(1)=1.18±0.30±0.12 R2(1)=0.71±0.22±0.07 measured by BaBar R1(1)=1.128±0.060±0.025 R2(1)=0.920±0.048±0.013 used in the world average R1,R2 uncertainty is the major source of systematics onrA2 E. Barberio

  11. Extracting F(1)Vcb OPAL CLEOBd0D*- andB-D*0- BABAR BELLE hA1(w) |Vcb| x 10-3 w w w E. Barberio

  12. F (1)|Vcb| world average F(1)|Vcb|=(37.80.9)x10-3rA2 =1.540.14 E. Barberio

  13. +0.024 +0.017 F(1) =0.913 -0.017 -0.030 F(1) and Vcb non-perturbative QCD calculations F(1) =0.9070.0070.0250.017 F(1) =0.9000.0150.0250.025 future error reduction from unquenched calculations from lattice and sum rule F(1)=0.91  0.04 |Vcb|excl=(41.51.0exp1.8theo) 10-3 E. Barberio

  14. Vcb from Bd0D+- decays BELLE large combinatorial background non-zero 1/mQ corrections to G(1) consistency check and test of the theory: from Belle D* and D+ results r2D-r2D*=-0.230.29 0.20 G(1)/F(1)=1.160.14 0.12 compatible with expectations G(1)|Vcb|=(42.03.7) x 10-3 rG2=1.15  0.16 E. Barberio

  15. Bd0D*- and Bd0D+- The Bd0D*- and Bd0D+- branching fraction are derived from the same analyses used for Vcb E. Barberio

  16. Vcb from inclusive semileptonic decays L l1l2or mp2mG2 at 1/mb2 rD3,rLS3 or r1,r2,T1-4 at1/mb3 exp. D|Vcb|<1% Gsldescribed by Heavy Quark Expansion in (1/mb)n and ask non perturbative parameters need to be measured and arise at each order expansions depend on mb definition: different expansions different non-perturbative terms, but they related pole mass low scale running quark masses E. Barberio

  17. inclusive Vcb rate b |Vcb| shape mb,mc m2G,m2p shape non-perturbative parameters though the shape ‘moments’ Difficulty to go from the measured shape to the true shape: shape in B rest frame, QED corrections, detector resolution, accessible phase space, etc E. Barberio

  18. Rate: bXc- branching fraction esig e- Bsig Btag e+ etag ν U(4S) experiments traditionaly use di-lepton technique: To reduce the error due to the experimental spectrum cut-off (modelling) E. Barberio

  19. Rate: bXc- branching fraction BXn B B 0 n p U(4S) l- g K 0 g p B-factoies more data  new tecknique: B-meson fully reconstructed Belle The inclusive B+ and B0 semileptonic branching fractions measured separately: B(B0Xln) = (10.320.32 0.29)% B(B+Xln) = (11.920.26 0.32)% E. Barberio

  20. Inclusive semileptonic branching fractions Partial BF main sys from modelling LEP: BR(BXc -) = (10.420.26) 10-2 E. Barberio

  21. Shape: moments of kinematics variables how much is there? (area) where is it? (mean) how wide is it? (width) skewness E. Barberio

  22. moments in semileptonic decays E : lepton energy spectrum in BXc n(BaBar Belle CLEO DELPHI) MX 2: hadronic mass spectrum in BXc n (BaBar CDF CLEO DELPHI) Eg : photon energy spectrum in BXsg (Belle CLEO) On=1,2,..: different sensitivities to non-perturbative parameters evaluated on the full spectrum or part of it (p > pmin) in the B rest frame OPE predictions can be compared with experiments after smearing  integration over neutrino and lepton phase space provides smearing over the invariant hadronic mass of the final state: test of OPE predictions, quark-hadron duality higher moments used to get sensitivity to 1/mb3parameters: reduced uncertainty on |Vcb| from inclusive semileptonic decay E. Barberio

  23. photon energy spectrum u, c, t Belle Eg>1.8 GeV Eg>2 GeV photon energy spectrum in BXsg not sensitive to new physics and give information on B structure CLEO E. Barberio

  24. CLEO: hadronic moments CLEO 3.2 fb-1 MX2 P*min= 1.5 GeV hadronic mass spectra Mx photon and hadronic mass spectrum evaluated at 1/mB3 andas2bo [Ligeti,Luke,Manohar,Wise][Falk,Luke,Savage] Mx from ln: MX2 = mB2+mn2-2EBEn fit relative contributions of D,D*,D** L = 0.350.07  0.1 GeV l1=-0.238 0.0710.078 GeV2 E. Barberio

  25. BaBar Belle: hadronic moments BABAR BABAR 51 fb-1 D, D* Events/0.5 GeV2 high mass charm states Mx2[GeV2/c4] B-factories, lower lepton momentum cutoff in the B rest frame: small B boost, larger statistics, fully reconstructed sample fit relative contributions of D,D*,D** lepton cutoff P*>0.9 GeV for both Belle 140 fb-1 Belle preliminary E. Barberio

  26. CDF: hadronic moments B  Dln B  D*ln B  D**ln B  Dpln P*>0.7 GeV M(D*+p) D and D* well measured  determine contribution to moments from high mass components hadronic mass spectra Mx CDF fixes D,D* contribution and measures the D** rate: CDF n.b. details of resonances not included in parton level calculation • = 0.39 + 0.0750stat+ 0.026exp +0.064BR +0.058theo GeV l1=-0.182 + 0.055stat+ 0.016exp +0.022BR +0.077theo GeV2 E. Barberio

  27. Bd0D**- decays exclusively reconstructed D**D+- D**D*+- D**D0+ LEP: hadronic moments large momentum of b-hadron ~30 GeV: full lepton energy spectrum in B rest frame  non-truncated spectra M=M(D(*))-M(D(*))fits with resonant and non resonant states E. Barberio

  28. First and second hadronic moment preliminary Belle preliminary BaBar measure also the 3rd and 4th moment DELPHI the third E. Barberio

  29. CLEO: lepton moments Gremm,Kapustin 1s theo. spectra background subtracted ratios of truncated lepton spectra e m Cleo photon, hadronic mass and lepton energy spectrumevaluated at 1/mB3andas2bo L=0.39+0.03stat+0.06sys+0.12th GeV l1=-0.25+0.02stat+0.05sys+0.14th GeV2 from 1/mB3 + as E. Barberio

  30. BaBar: lepton moments BABAR 47+9 fb-1 156,000 e± B-factories, lower lepton momentum cut in the B rest frame: small B boost and larger statistics BaBar uses the di-lepton sample E. Barberio

  31. Belle: lepton moments B0 B+ B+ B0 5054±145 8371±209 Belle fully reconstructed sample: B+ & B0 studied separately 140 fb-1 preliminary preliminary unfolded spectra P* >0.6 GeV P* [GeV] E. Barberio

  32. background subtracted unfolded spectrum e+m LEP: lepton energy spectrum large momentum of b-hadron ~30 GeV: full lepton energy spectrum in B rest frame  non-truncated spectra lepton spectrum First three moments: M1 = 1.383 0.012stat0.009sys GeV M2 = 0.192 0.005stat0.008sys GeV2 M3 =-0.0290.005stat0.006sys GeV3 E. Barberio

  33. mp2 (GeV2) rD3 (GeV3) mb(GeV) mb(GeV) M1(Mx) M2(Mx) M3(Mx) M1(El) M2(El) M3(El) DELPHI: parameter extraction multi-parameter c2 fit to determine relevant 1/mb3 parameters Phy.Lett B556(2003)41 c2/d.o.f.=0.96 input: mG2= 0.35 +0.05 GeV2 rLS3= -0.15 +0.15 GeV3 mc= 1.05  0.30 GeV mb= 4.57  0.10 GeV equivalent to B Xsg mb,kin(1GeV)= 4.59 +0.08fit+0.01sys GeV mc,kin(1GeV)= 1.13 +0.13fit+0.03sys GeV mp2 (1GeV) = 0.31 +0.07fit+0.02sys GeV2 rD3 (1GeV) = 0.05 +0.04fit+0.01sys GeV3 mb(mb)= 4.233 GeV mc(mc)= 1.245 GeV present accuracy: no need of higher order terms L = 0.40 + 0.10fit+ 0.02sys GeV l1=-0.15 + 0.07fit+ 0.03sys GeV2 r1=-0.01 + 0.03fit+ 0.03sys GeV3 r2= 0.03 + 0.03fit + 0.01sys GeV3 pole mass expansion: (compatible with CLEO) similar results with mb1S-l1 formalism Bauer, Ligeti, Luke, Manohar E. Barberio

  34. BaBaR: parameters extraction BABAR: up to 1/mb3:fit all parameter and Vcb at the same time P.Gambino, N.Uraltsev o= used,•= unusedin the nominal fit BABAR MX moments hep-ph/0401063 hep-ph/0403166 M1x M2x M4x M3x c2/ndf =20/15 M2l M3l M1l M0l Red line: HQE fitYellow band: theory errors E. Barberio

  35. BABAR Another parameters extraction Fit with all data in (except Belle) from Bauer, Ligeti, Luke, Manhoar, Trott (hep-ph/040800) Using the expansion in mb1S : Vcb=(41.00.40.1t)10-3 mb1S=(4.680.03) GeV mb from Babar fit (fifferent mb scheeme): E. Barberio

  36. Conclusion |Vcb| from exclusive B decays Limited by the error onF(1)=1: will reduce by lattice calculations, not soon We need to understand the “experimental” spread of F(1)Vcb Bd0D(*)- precision systematics limited: slow p, D’s BR, D**? |Vcb|excl=(40.1 0.9exp 1.8theo) 10-3 |Vcb| from inclusive B decays Constraints on non-perturbative parameters reduce the uncertainty to ~2.% BR(BXc-) and tB are very precise Quark-hadron duality violation? no evidence with the present sensitivity. Different experiments are now providing many measurements: they are all consistent. Belle measures B+ and B0 separately. E. Barberio

  37. Summary of BABAR Results on |Vcb| Exp. Determination of Quark Masses Recent Measurements of |Vcb| BABAR inclusive BABAR BABAR (D*l n) exclusive Conversion to MS scheme (N. Uraltsev) E. Barberio

  38. G(bXcln) U(4S): BR(BXc -) = (10.830.25) 10-2 tB = (1.5980.01) ps GBXc -= (0.4460.0100.003)10-10 MeV LEP: BR(BXc -) = (10.420.26) 10-2 tb = (1.573  0.01) ps GBXc -= (0.4360.010 0.006)10-10 MeV Word average GBXc-= (0.441 0.008) 10-10 MeV E. Barberio

  39. derivation of inclusive Vcb |Vcb| = 41.9 [1±0.009Gsl±0.010fit±0.005pert]10-3 as scale mb,mc,mp2,mG2,rD3,rLS3 Vcb dependence on non-perturbative parameters in running quark mass scheme: N.Uraltsev hep-ph/0302262 |Vcb| = |Vcb|0 {1 -0.65[ mb(1)-4.6 GeV] + 0.4 [mc(1)-1.15 GeV] + 0.01[mp2- 0.4 GeV2] + 0.10 [rD3 -0.12 GeV3] + 0.05[mG2- 0.35GeV2] - 0.01 [rLS3+ 0.15 GeV3] } using sl(world) and Babar: E. Barberio

  40. Systematics BELLE CLEO E. Barberio

  41. Systematics LEP E. Barberio

  42. E. Barberio

  43. CKM mixing matrix Wolfenstein parameterization: unitarity (A†A = 1) E. Barberio

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