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σ |V ub | at a Super Flavor Factory

σ |V ub | at a Super Flavor Factory. Benoit VIAUD LAL, CNRS-In2p3. Super Flavor Factory. Generically: similar to BaBar/Belle, with L  100 = 75 ab -1. I focus in this talk on the Italian project: SuperB. Crab waists and Large Piwinski angle to reach L=10 36 cm -2 s -1

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σ |V ub | at a Super Flavor Factory

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  1. σ|Vub|at a Super Flavor Factory Benoit VIAUD LAL, CNRS-In2p3 B. VIAUD,VIth infn B-physics mting , Ferrara

  2. Super Flavor Factory • Generically: similar to BaBar/Belle, with L  100 = 75 ab-1 • I focus in this talk on the Italian project: SuperB. • Crab waists and Large Piwinski angle to reach L=1036cm-2s-1 •  =0.28 instead of 0.56. • Smaller boost (better hermeticity) and improved vertex detector New Layer 0 at 1.2 cm from the beam) : improved neutrino and background rejection. • Start ~ in 2015: theory should be improved by then. CDR : http://www.pi.infn.it/SuperB/?q=CDR Last Workshop : http://events.lal.in2p3.fr/conferences/SuperB09/ B. VIAUD,VIth infn B-physics mting , Ferrara

  3. Error on |Vub| @ SuperB ?? • Today: |Vub| is no longer dominated by stat. • SuperB (75ab-1): stat does not count anymore. • Predicting what can be achieved at a Super Flavor Factory means predicting how the systematic and theoretical uncertainties will be reduced. • Single reliable way: Full MC studies -> not yet possible. • Single available way: Educated guesses (science fiction ?) • So many experimental and theoretical analyses that it is very hard to consider them all. • => Choose a few (promising) ones and extrapolate. B. VIAUD,VIth infn B-physics mting , Ferrara

  4. |Vub| from inclusive B-> Xu l v decays B. VIAUD,VIth infn B-physics mting , Ferrara

  5. Inclusive |Vub| • Total decay rate precisely known • OPE+HQE, expansion in (1/mb)k and (s)k •  dominated by 2.5mb/mb : ~3% • Not used up to now • ulv/ clv ~ 1/50 : harsh cuts necessary • OPE convergence spoiled in restricted part of the phase space • Must deal with the Fermi motion of the b inside the B B. VIAUD,VIth infn B-physics mting , Ferrara

  6. Many Theoretical Approaches • Have to deal with Shape Functions (SF) • to account for the Fermi motion • BNLP (PRD71:073006 (2005)) • GGOU (JHEP 10(2007)058 ) • LNR (JHEP 0510:084 (2005)), LLR (PLB 486:86) • Dressed Gluon Exponentiation (DGE) (JHEP 0601:097 (2006)) • Analytic Coupling (AC) (PRD74:034006 (2006)) • Various ways to treat the SF • In a OPE, convoluted with pert. quantities and parameterized with their shape constrained from moments = f( =MB-mb ; 2 ) • Take it from B-> Xs • Calculate it • Various treatments of the subleading SF (universal only at LO in 1/mb) B. VIAUD,VIth infn B-physics mting , Ferrara

  7. Many Theoretical Approaches • Have to deal with Shape Functions (SF) • to account for the Fermi motion Key common points: • Consistent results • BNLP (PRD71:073006 (2005)) • GGOU (JHEP 10(2007)058 ) • Main source of • Uncertainty on |Vub| • LNR (JHEP 0510:084 (2005)), LLR (PLB 486:86) • Dressed Gluon Exponentiation (DGE) (JHEP 0601:097 (2006)) • Analytic Coupling (AC) (PRD74:034006 (2006)) • Dominant source: mb and 2 •  ~ 4mb/mb • Determined from fits to the moments of • B-> Xclv and Xs spectra. • Various ways to treat the SF • In a OPE, convoluted with pert. quantities and parameterized with their shape constrained from moments = f( =MB-mb ; 2 ) • Take it from B-> Xs • Calculate it • Various treatments of the subleading SF (universal only at LO in 1/mb) B. VIAUD,VIth infn B-physics mting , Ferrara

  8. Many Experimental Approaches • Try several cut variables to find the best • trade-off between S/B and th No Tag Hadronic Tag Hadronic Tag Hadronic Tag B. VIAUD,VIth infn B-physics mting , Ferrara

  9. Many Experimental Approaches Untagged Semileptonic tag Hadronic tag oFirst find a Btag, then look for B->Xulv in its recoil: - Only one Xu-l pair in the rest of event - No other tracks, small residual energy o tag side: B->D(*)+(π±,K±), full reco. (many modes) o Well defined event: full kinematics, charge, flavor. o Only one neutrino : precise reco of m2miss ,miss ,q2, MX, P+ o tag side: B->D(*)lν o tag-B kinematics incomplete: 2 ν High signal statistics, More sensitive to Background simulation CleanSample, Better systematics + Purity + Efficiency B. VIAUD,VIth infn B-physics mting , Ferrara

  10. Many Experimental Approaches Key common points: • Consistent results • Leading Uncertainties on |Vub| • Detector effects (Tracking and PID efficiency) • Fit and Efficiency on the tag side • Knowledge of the B->Xc l v backgrounds B. VIAUD,VIth infn B-physics mting , Ferrara

  11. Many Experimental Approaches Key common points: • Consistent results • Leading Uncertainties on |Vub| Improved @ SuperB - Large control samples - Improved detector & bkg rejection • Detector effects (Tracking and PID efficiency) • Fit and Efficiency on the tag side • Knowledge of the B->Xc l v backgrounds B. VIAUD,VIth infn B-physics mting , Ferrara

  12. Babar, PRL 100, 171802 (2008) MX Analysis • First reconstruct the hadronic tag Btag B+tag B0tag • Look for the signal in Btag’s recoil • One lepton with PBframe > 1 GeV/c • Ql consistent with Btag’s flavor, evtQ = 0 Good  rejects B -> Xclv • mmiss2 < 0.5 GeV2, miss • Mveto2 = (pB- pD*-pl) < 3GeV2, pD* from slow pion 383 MBB Bsig • Kinematic fit: MX~250 MeV • Combinatoric background: fit to mES in bins of MX 1.55 GeV • Binned X2 fit of B -> Xulv & B -> Xclv • MC distrib. to MX data distrib. B. VIAUD,VIth infn B-physics mting , Ferrara

  13. MX Analysis • First reconstruct the hadronic tag Btag B+tag B0tag • Look for the signal in Btag’s recoil • One lepton with PBframe > 1 GeV/c • Ql consistent with Btag’s flavor, evtQ = 0 Good  rejects B -> Xclv • mmiss2 < 0.5 GeV2 • Mveto2 = (pB- pD*-pl) < 3GeV2, pD* from slow pion 383 MBB Bsig • Kinematic fit: MX~250 MeV • Combinatoric background: fit to mES in bins of MX • Binned X2 fit of B -> Xulv & B -> Xclv • MC distrib. to MX data distrib. |Vub|= 4.27 +/- 0.16stat +/- 0.15syst +/- 0.30th (BNLP) B. VIAUD,VIth infn B-physics mting , Ferrara

  14. MX Analysis: Error Breakdown Errors on BF @ SuperB 1 % • Data Stat + MC stat: 8% + 3.22 % • Detector Effects : 2 % 1 % • Improved with high stat control samples+ better det • Signal Model (SF & gluon split.): 2 % 1 % • Improved better mb, Xs meas. and th. • BF(B->u lv excl.): 2 % 1 % • Improved by > ½ @ SuperB (cf this talk) • BF & FF (B->c lv excl.): 1.2% 0.3 % • Idem (cf this talk) • mES fit (parameterization choice): 3.7% 1.5 % Tot: 12 % 2.5 % • Better stat + possibility to be more selective for Btag will help. |Vub|exp: 6 % ~1.5 % B. VIAUD,VIth infn B-physics mting , Ferrara

  15. MX Analysis: Error Breakdown • Crucial it we want to use a looser MX cut to reduce th. • Improved with a precise measurement of BF(B-c l v) @ SuperB • (back-up slides). • Better detector. • Lower  => hermeticity  => better v => better bkg rejection • Better Vertexing => B-D separation to veto B->D X l v • Hope corresponding  can be divided by ~4. Errors on BF @ SuperB 1 % • Data Stat + MC stat: 8% + 3.22 % • Detector Effects : 2 % 1 % • Improved with high stat control samples+ better det • Signal Model (SF & gluon split.): 2 % 1 % • Improved better Xs meas. and th. • BF(B->u lv excl.): 2 % 1 % • Improved by > ½ @ SuperB (cf this talk) • BF & FF (B->Xc l v excl.): 1.2% 0.3 % • Idem (cf this talk) • mES fit (parameterization choice): 3.7% 1.5 % Tot: 12 % 2.5 % • Better stat + possibility to be more selective for Btag will help. |Vub|exp: 6 % ~1.5 % B. VIAUD,VIth infn B-physics mting , Ferrara

  16. Total Error on |Vub| @ SuperB HFAG, ICHEP 2008, GGOU |Vub|(%) = 3.7 3.9.  1.8  2.5 + 0.-3.1+1.3-0.6 Higher order pert. and non pert. corrections Hadronic param. (mb) q2 tail and Weak Annihil. SF parame-terization Exp. SuperB, > 2015 ?? ?? ?? ?? 1.5 Question to theorists: what can we hope here ? B. VIAUD,VIth infn B-physics mting , Ferrara

  17. (mb) by SuperB’s time • Measured via a fit to the moments of incl. B->Xc l v and B->Xs spectra. • Total BF (OPE) = Hadronic, non calculable, parameters. Multiplied by perturbative coefficients. • Similar expressions for moments, as a function of a cut lepton energy. Hadr. System Mass Lepton energy Photon energy f( mb, 2,…) => fit to extract these hadronic parameters B. VIAUD,VIth infn B-physics mting , Ferrara

  18. (mb) by SuperB’s time • Example: BaBar (arXiv:0707.2670v1) B. VIAUD,VIth infn B-physics mting , Ferrara

  19. (mb) by SuperB’s time • HFAG 2008, Kinetic scheme (mb) ~ 30-50 MeV • Theoretical Uncertainties dominate • Moment Measurements: syst ~ stat • systdominated by the determination of efficiencies • Additional, higher order moments ? At SuperB, > 2015 exp  ½ (?) B. VIAUD,VIth infn B-physics mting , Ferrara

  20. (mb) by SuperB’s time • HFAG 2008, Kinetic scheme (mb) ~ 30-50 MeV • Recent th. progresses to be included in the fit: • O(2s) calc. of leading power rate and moments • O(s) calc. 1/mb2 power correction • LO calc. of 1/mb4 Should remove a large part of th Can we hope (mb) ~ 20 MeV by 2015 ? • With these improvements • + potential still-higher order corrections • + B->Xs  puzzle solved • + Consistency between 1S and kinetic schemes B. VIAUD,VIth infn B-physics mting , Ferrara

  21. Total Error on |Vub| @ SuperB HFAG, ICHEP 2008, GGOU |Vub|(%) = 3.7 3.9.  1.8  2.5 + 0.-3.1+1.3-0.6 Higher order pert. and non pert. corrections Hadronic param. (mb) q2 tail and Weak Annihil. SF parame-terization Exp. SuperB, > 2015 ?? ?? ?? 2. 1.5 Include more Terms ? Cut high q2 ? B. VIAUD,VIth infn B-physics mting , Ferrara

  22. Total Error on |Vub| @ SuperB HFAG, ICHEP 2008, GGOU |Vub|(%) = 3.7 3.9.  1.8  2.5 + 0.-3.1+1.3-0.6 Higher order pert. and non pert. corrections Hadronic param. (mb) q2 tail and Weak Annihil. SF parame-terization Exp. SuperB, > 2015 0.5 1 1.5 2 1.5 ½ Realistic ? If not, what can we expect ? B. VIAUD,VIth infn B-physics mting , Ferrara

  23. Total Error on |Vub| @ SuperB HFAG, ICHEP 2008, GGOU |Vub|(%) = 3.7 3.9.  1.8  2.5 + 0.-3.1+1.3-0.6 Higher order pert. and non pert. corrections Hadronic param. (mb) q2 tail and Weak Annihil. SF parame-terization Exp. SuperB, > 2015 If yes: |Vub| ~ 3 % @ SuperB ! B. VIAUD,VIth infn B-physics mting , Ferrara

  24. |Vub| @ SuperB • Another option: Use the full decay rate • Pioneer Analysis at Babar (88 MBB, hep-ex/0601046v2) • Hadronic Tag • Similar to the MX analysis already presented here. Errors on Vub At SuperB -|Vub|exp ~ 2.5 % -|Vub|th ~ 2.5*mb/mb ~ 1% => |Vub|~3 % 88 fb-1 75 ab-1 18.6% 1% 3.8% 1% Signal Model 5.6% 1.5% 3.8% 1% B. VIAUD,VIth infn B-physics mting , Ferrara

  25. |Vub| from exclusive B-> Xu l v decays B. VIAUD,VIth infn B-physics mting , Ferrara

  26. Exclusive |Vub| • Harder than the inclusive case: • -> need to fully describe specific hadrons • Needs Form Factors from theory • Unquenched LQCD (q2 > 16 GeV2): HPQCD[1], FNAL[2] • LCSR (q2 < 16 GeV2): Ball-Zwicky[3] • Th. uncertainties are the main source of |Vub| (~12%) [1] Gulez & al, hep-lat/0601021 [2] Okamoto & al, hep-lat/0409116 [3] Ball & al, hep-ph/0406232 B. VIAUD,VIth infn B-physics mting , Ferrara

  27. Exclusive |Vub| • Golden Mode: B-> l v , • both for th. and exp. • Measured BF(B-> l v ) : • -> already syst ~ stat • -> better syst will again be the • challenge at SuperB • -> Hadronic Tag ! HFAG’s Average (FNAL) |Vub|= (3.55±0.22 +0.6-0.4 )10-3 th~6% th~12% B. VIAUD,VIth infn B-physics mting , Ferrara

  28. Exclusive |Vub| with an Hadronic Tag @ SuperB Extrapolation from a recent analysis by Belle (arXiv:0812.1414v1) • 657 MBB • Hadron Tag, tight cuts on E and mES (no fit) • Signal extraction: • -binned fit to the mmiss2 distribution • Statistically limited, but low syst : <5% B(B->+lv) = 1.12  0.18  0.05 B(q2>16GeV2) = 0.26  0.08  0.01 • Leading syst: Detector effects / B->Xulv and Xclv FF & BF / BB initial yield. • With : Large Control sample / Improved meas. and th, harsher cuts => Cab hope to reduce systby ~1/3 at Super B B. VIAUD,VIth infn B-physics mting , Ferrara

  29. Exclusive |Vub| with an Hadronic Tag @ SuperB Extrapolation from a recent analysis by Belle (arXiv:0812.1414v1) • 657 MBB • Hadron Tag, tight cuts on E and mES (no fit) • Signal extraction: • -binned fit to the mmiss2 distribution • Statistically limited, but low syst : <5% B(B->+lv) = 1.12  0.18  0.05 B(q2>16GeV2) = 0.26  0.08  0.01 • Leading syst: Detector effects / B->Xulv and Xclv FF & BF / BB initial yield. At SuperB, with q2 > 16 GeV2 : - (B)stat ~ 3% and (B)syst~ 3% => (B)exp~ 5% => (|Vub|)exp ~ 2.5 % • With : Large Control sample / Improved meas. and th, harsher cuts => Cab hope to reduce systby ~1/3 at Super B B. VIAUD,VIth infn B-physics mting , Ferrara

  30. |Vub|th : What improvement from LQCD ? See Appendix A of the SuperB CDR. Sources of uncertainties: • Statistical (number of configurations) • Matching to continuum (pert. calculations • difficult on the Lattice) • Chiral extrapolation (computation  time if mq) • Heavy quark treatment All sources would benefit from an improved CPU. With the following evolutions: - Lattice spacing a : 0.1 fm -> 0.03 fm - light quark mq : 1/2–1/6 ms -> 1/12 ms - Lattice size L : 3 fm -> 4.5 fm f+ ~2-3% B. VIAUD,VIth infn B-physics mting , Ferrara

  31. |Vub|th : What improvement from LQCD ? See Appendix A of the SuperB CDR. Sources of uncertainties: • Statistical (number of configurations) • Matching to continuum (pert. calculations • difficult on the Lattice) • Chiral extrapolation (computation  time if mq) • Heavy quark treatment All sources would benefit from an improved CPU. Cost: few PFLOPs-years With the following evolutions: - Lattice spacing a : 0.1 fm -> 0.03 fm - light quark mq : 1/2–1/6 ms -> 1/12 ms - Lattice size L : 3 fm -> 4.5 fm |Vub|th~2-3% B. VIAUD,VIth infn B-physics mting , Ferrara

  32. |Vub|th : What improvement from LQCD ? See Appendix A of the SuperB CDR. Evolution law of computers performance with time => Machines available for LQCD could improve from 1-10 TFLops to 1-10 PFlops => |Vub|th~2-3% looks feasible ! B. VIAUD,VIth infn B-physics mting , Ferrara

  33. Exclusive |Vub|: All together With |Vub|exp~2-3 % and |Vub|th~2-3% => |Vub|tot ~ 4 % seems feasible. B. VIAUD,VIth infn B-physics mting , Ferrara

  34. Conclusion • Stat. uncertainty on |Vub|th will be marginal at a Super Flavor Factory • To reach |Vub|~ few percents: big effort to reduce the systematic and theoretical uncertainties. • Systematic uncertainties will benefit from the large data sample: • Hadronic tag methods not statistically limited any longer • Control Samples to reduce detector effects • Better knowledge of the B->Xc l v backgrounds • Theoretical uncertainties • Inclusive: Need to improve mb (~20MeV ?) • Exclusive: Large improvement of the computing power should help LQCD |Vub|~3 % (incl.) and |Vub|th ~4% (excl.) seems possible ! B. VIAUD,VIth infn B-physics mting , Ferrara

  35. Back-up B. VIAUD,VIth infn B-physics mting , Ferrara

  36. Improved B->Xc l v BF’s • The control of these backgrounds is essential for any inclusive |Vub| determination. • What improvement at SuperB ? • Study one example: B->D(*)()lv with a hadronic tag (Babar, arXiv:0712.3503v1) • Hadronic Tag • BF measured with respect to the total semileptonic BF. • N(Xlv): fit to mES • Nsig: fit to the mmiss2 distribution B. VIAUD,VIth infn B-physics mting , Ferrara

  37. Improved B->Xc l v BF’s • The control of these backgrounds is essential for any inclusive |Vub| determination. • What improvement at SuperB ? • Study one example: B->D(*)()lv with a hadronic tag (Babar, arXiv:0712.3503v1) • Hadronic Tag • BF measured with respect to the total semileptonic BF. • N(Xlv): fit to mES • Nsig: fit to the mmiss2 distribution B. VIAUD,VIth infn B-physics mting , Ferrara

  38. Improved B->Xc l v BF’s • The control of these backgrounds is essential for any inclusive |Vub| determination. • What improvement at SuperB ? • Study one example: B->D(*)()lv with a hadronic tag (Babar, arXiv:0712.3503v1) • Hadronic Tag • BF measured with respect to the total semileptonic BF. • N(Xlv): fit to mES • Nsig: fit to the mmiss2 distribution Systematic uncertainties • Detector Effects • Btag efficiency • BF(D) Can hope 1/2-1/3 with SuperB statistics B. VIAUD,VIth infn B-physics mting , Ferrara

  39. Improved B->Xc l v BF’s @ SuperB PDG 2006 (%) Babar hadr. Tag • B- -> D0 l v 2.2 +/- 0.11 2.33 +/- 0.09 +/- 0.09 +/- 0.03 +/- 0.10 • B- -> D0* l v 5.83 +/- 0.15 +/- 0.30 5.7 +/- 0.18 2.21 +/- 0.11 +/- 0.12 +/- 0.04 • B0 -> D+ l v 2.2 +/- 0.12 +/- 0.08 5.49 +/- 0.16 +/- 0.25 • B0 -> D+* l v 5.0 +/- 0.10 • B- -> D+ -l v 0.42 +/- 0.06 +/- 0.03 +/- 0.01 0.6 +/- 0.05 • B- -> D*+ -l v 0.4 +/- 0.05 0.59 +/- 0.05 +/- 0.04 +/- 0.01 +/- 0.01 • B0 -> D0 -l v 0.4 +/- 0.06 0.43 +/- 0.08 +/- 0.03 +/- 0.01 • B0 -> D0* -l v 0.48 +/- 0.08 +/- 0.04 0.5 +/- 0.08 B. VIAUD,VIth infn B-physics mting , Ferrara

  40. MX Analysis: Error Breakdown Errors on BF @ SuperB 1 % • Data Stat + MC stat: 8% + 3.22 % • Detector Effects : 2 % 1 % • Improved with high stat control samples+ better det • Signal Model (SF & gluon split.): 2 % 1 % • Improved better Xs meas. and th. • BF(B->u lv excl.): 2 % 1 % • Improved by > ½ @ SuperB (cf this talk) • BF & FF (B->c lv excl.): 1.2% 0.3 % • Idem (cf this talk) • mES fit (parameterization choice): 3.7% 1.5 % Tot: 12 % 2.5 % • Better stat + possibility to be more selective for Btag will help. |Vub|exp: 6 % ~1.5 % B. VIAUD,VIth infn B-physics mting , Ferrara

  41. [1] Ball & al, hep-ph/0406232 [2] Becirevic & al, Phys. Lett. B478, 417 [3] Ex: Becher&Hill, hep-ph/0509090 [4] P. Ball, hep-ph/0611108 Form Factors (|Vub|)expcould be further improved using the full measured q2 spectrum. Parameterizations of the FF shape to extend theoretical predictions to the whole q2 spectrum… -Ball-Zwicky (BZ)[1] -Becirevic-Kaidalov (BK)[2] -Boyd/Grinstrin/Lebed+Hill/Becher (BGL)[3] Linear or more ?? BaBar, loose v, 206 fb-1, hep-ex/0612020 Data points not yet precise enough. Fits give the same result whatever the parameterization Using constraints from unitarity and from a fit to data and theoretical points, enough ai’s could be known to yield a precise parameterization. B. VIAUD,VIth infn B-physics mting , Ferrara

  42. Many Theoretical Approaches • BNLP • OPE+HQE, expansion in (1/mb)k and (s)k • Fermi motion included via Shape Functions (SF) • SF convoluted with perturbative quantities, at each order in 1/mb • SF not calculated from first principles, but shape of the leading ones constrained by their (known) 1st , 2nd moments : =MB-mb ; 2 • Subleading SF’s showing up at each higher term in (1/mb) accounted for by trying many ad-hoc parameterizations. B. VIAUD,VIth infn B-physics mting , Ferrara

  43. Many Theoretical Approaches • BNLP • OPE+HQE, expansion in (1/mb)k and (s)k • Fermi motion included via Shape Functions (SF) • SF convoluted with perturbative quantities, at each order in 1/mb • SF not calculated from first principles, but shape of the leading ones constrained by their (known) 1st , 2nd moments : Hadronic param. extracted from the moments of B->Xclv and B->Xs  spectra. Dominates |Vub| =MB-mb ; 2 B. VIAUD,VIth infn B-physics mting , Ferrara

  44. BaBar, 206 fb-1, hep-ex/0612020 Untagged B0->π-l+ν, loose ν-reconstruction No tight ν-reconstruction cuts : Signal Yield ↑ Purity ↓ High statistics allow a precise signal extraction in 12 q2 bins • Binned fit to ΔE-mES: renormalize histos from MC. High stat. also allows to control the systematics despite low S/B… -Bkg fitted in q2 bins: reduced σ from B->Xlv FF&BF (leading at high q2) -High stat. in data control samples: continuum bkg correction (leading at low q2) Total Nsig~5000 In q2 bins: Nsig ~ 430 to 500 S/B ~ 1/3 to 1/10 B(B->-lv)= (1.46±0.07stat±0.08syst)10-4 ΔB(B->-lv; q2>16GeV2)= (0.38±0.04stat±0.03syst)10-4 4.8% 5.5% |Vub|= ( 3.7±0.2±0.2+0.6-0.4 )10-3 FNAL B. VIAUD,VIth infn B-physics mting , Ferrara

  45. Status of BF’s and |Vub| Belle, semileptonic tags, B++B0 |Vub|= ( 3.6±0.41±0.20+0.6-0.4 )10-3 FNAL Babar, semileptonic+hadronic , B++B0 |Vub|= ( 4.0±0.5 ± 0.3+0.7-0.5 )10-3 FNAL CLEO, untagged |Vub|= (3.6±0.4 ±0.20+0.6-0.4 )10-3 HPQCD Babar Loose-v 1.37±0.15±0.11 |Vub|= (3.7±0.20±0.20+0.6-0.4 )10-3 FNAL Error on the FF determination dominates the most precise results. What improvements with the full B-factories dataset ? B. VIAUD,VIth infn B-physics mting , Ferrara

  46. few definitions… In the Y(4S) frame: EB, pB= nominal values of the B energy and momentum, from 4-mom. conservation pY = pπ+pl |cosθBY| and |cos2ΦB| <1 if the ν’s are the only undetected particles… B. VIAUD,VIth infn B-physics mting , Ferrara

  47. Results: Relative Errors on ΔBF(q2) -Dominant syst. errors: Detector effects, Continuum description -Fit of the backgrounds yields in several q2 bins (thanks to high statistics due to loose ν ) => reduced systematic error due backgrounds BF and FF. B. VIAUD,VIth infn B-physics mting , Ferrara

  48. [1] Gulez & al, hep-lat/0601021 [2] Okamoto & al, hep-lat/0409116 [3] Ball & al, hep-ph/0406232 [4] Scora & al, hep-ph/9503486 Form Factors => Boyd/Grinstrin/Lebed+Hill/Becher (BGL) Babar’s untagged measurement Full dataset ! Most improved points: High / Low z Improved Continuum Improved B->Xul v background) Unitarity: Should obtain a very precise determination of the FF’s shape with a fit to the ΔB(q2) measurements, helped by theoretical constraints (like unitarity). In that case, LCSR and LQCD have to provide only the normalization f+(0). Even closer with the full dataset… B. VIAUD,VIth infn B-physics mting , Ferrara

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