The Future of V ub Antonio Limosani JSPS Fellow (KEK-IPNS JAPAN) 2010 2006 BMN 2006 BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 1
Motivation Fundamental parameter in SM L SM =...+ gw µ + b L γ µ V ub u L +... CKM mixing matrix element V ud V us V ub V cd V cs V cb V td V ts V tb Unitarity Triangle Side-length V ud V ub * ϕ 2 (α) V td V tb * ϕ 3 (γ ) ϕ 1 (β) V cd V cb * Directly test the mechanism for CP Violation in SM BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 2
1. Cuts to avoid B X c l ν p l > (M 2 B M 2 D ) 2M B 2. Measure Measurement type - Inclusive 2.3 GeV/c ( 10% phase space) q 2 > (M B M D ) 2 11 GeV 2 /c 2 ( 30%) M X < M D 1.8 GeV/c 2 ( 80%) B Charged lepton hadrons M X neutrino p lepton q 2 3. Extract V ub ΔB(B X u lν) = N Selected N Background ε Quark level BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 3
HFAG V ub Average Source Stat Exp Bkgd model Error (%) 2.2 2.8 1.9 Signal model 1.6 HQE: m b 4.2 SSF/matching WA Total 3.8 1.9 7.3 BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 4
Fully reconstructed B sample Dedicated exclusive channels are searched for in reconstruction 180 decay chains Clean environment but small sample Reconstruction Efficiency ~ 0.3% Reconstructed modes BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 5
Fully reconstructed B analysis Fully reconstruct the event 4-momenta of both B s are known Identify lepton from B Xlν on the signal side Use Particle ID to reconstruct the hadronic system and calculate Estimate the signal B X u lν BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 6
Belle M x Analysis @ 253/fb M x < 1.7 GeV/c 2 Phys.Rev.Lett.95:241801,2005 (hep-ex/0505088) ΔB=(1.24±0.11(stat) ±0.09(sys) ± 0.08(b->u) ±0.03(b->c))x10-3 V ub =4.09 x10-3 (1 ±0.049 (stat) ±0.035 (sys) ±0.031 (b->u) ±0.011 (b->c) ±0.045 (SF) ±0.038 (theory)) BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 7
M x Analysis : Statistical Error projections Luminosity(/ab) 0.25 1.0 5.0 50.0 Signal to Noise 0.65 1.5 2.0 2.0 B tag efficiency 0.3 0.4 0.6 0.6 V ub stat % 4.9 2.0 0.7 0.2 BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 8
M x Analysis : Systematic & Theory Error projections Luminosity(/ab) 0.25 1.0 5.0 50.0 Detector simulation 3.5 3.5 3.5 3.5 Background model (charm) 1.1 1.0 0.5 0.5 Signal model Extrapolating to full branching fraction (SF) Theory V ub : Matching scales, SSF Theory/Exp V ub : Weak Annihilation V ub stat % Depends of HQE parameters : b-quark mass, m b, dominates BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 9
M x Analysis : b-quark mass b-quark mass, m b (4.60 +/- 0.04) GeV/c 2 Luminosity(/ab) 0.25 1.0 5.0 50.0 Exp error: 0.025 0.02 0.01 0.01 Moments data Theory error 0.03 0.03 0.03 0.03 Vary α s, m b, m c Total error 0.04 0.04 0.03 0.03 Precision on m b hits theory floor! BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 10
M x Analysis : Systematic & Theory Error projections Luminosity(/ab) 0.25 1.0 5.0 50.0 Detector simulation 3.5 3.5 3.5 3.5 Background model (charm) 1.1 1.0 0.5 0.5 Signal model 3.1 2.8 2.6 2.4 Extrapolating to full branching fraction (SF) 4.5 4.2 3.9 3.7 Theory V ub : Matching scales, SSF Theory/Exp V ub : 3.0 2.0 1.0 1.0 Weak Annihilation BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 11
M x Analysis : Total Error projections Luminosity(/ab) 0.25 1.0 5.0 V ub total % 9.4 7.7 7.0 6.8 V ub exp % 6.1 4.1 V ub theory % 7.2 6.5 6.0 5.8 BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 12
M x Analysis : Total Error projections BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 13
V ub with Reduced Model dependence Phys.Rev.Lett. 96 (2006) 221801 (hep-ex/0601046 ) (BABAR Collaboration) M x < 2.5 GeV/c 2 V ub =3.84 x10-3 (1 ±0.182 (stat) ±0.036 (sys) ±0.056 (b->u) ±0.038 (b->c) ±0.000 (SF) ±0.026 (theory)) BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 14
Error projections Luminosity(/ab) 0.1 1.0 5.0 50.0 Statistics 18.2 5.7 2.6 0.8 Detector simulation Background model (charm) 3.8 3.5 2.0 2.0 Signal model 3.1 2.9 2.7 2.5 Extrapolating to full branching fraction (SF) 0.0 0.0 0.0 0.0 Theory V ub : Perturbative Total 19.5 8.9 6.6 6.1 BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 15
Error projections BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 16
Measurement types - Exclusive B pion π neutrino Experimentally less ambiguous than the inclusive decay Charged lepton q 2 Theoretical description parameterised by a single form factor db(b 0 π l + ν) dq 2 d(cosθ Wl ) V ub = p lepton = V ub 2 τ B 0 B(B (π / ρ)lν Γ thyτ B, G F 2 k π 3 Γ thy Form factor normalisation 32π 3 sin2 θ Wl f (q 2 ) 2 Determine Γ using unquenched lattice QCD calculations. Model independent Limited to q 2 >16 GeV 2 /c 2 BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 17
Current status - Exclusive BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 18
V ub from ΔB(B->πlv:q 2 >16) Three methods 1. Untagged: Systematic error 4% @ 0.2ab -1 (BABAR) Previous to this study consensus was one couldn t get lower than 8% 2. Semileptonic tag : Systematic error 10% @ 0.25ab -1 (Belle) Systematic dominated by statistics of control sample Total error 2.9% @ 5ab -1 and 2.1% @ 50ab -1 3. Full B reconstruction tag : Systematic error 2.1% @0.5ab -1 (Belle) Total error : 40% @0.5ab -1 (statistics dominated) Total error : 27% @1.0ab -1 Total error : 15% @5.0ab -1 (improvement in full recon efficiency) Total error : 5% @50ab -1 Theoretical uncertainties (Lattice QCD) Phys. Rev. D73:074502 (2006) Currently error is at 12%, but it s anticipated that it will reach 5%. BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 19
Future of Exclusive V ub BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 20
Future of V ub Tagged analyses are essential At logged luminosities of 5/ab and 50/ab precision is limited by systematic and theoretical uncertainties ~ 5% Co-ordinated experimental and theory studies are needed to reduce this error further b-quark mass BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 21
Backup Slides BNM Tsukuba (KEK) Sep 13-14 2006 Antonio Limosani KEK Slide 22