Semileptonic B Decays at BABAR

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1 Semileptonic B Decays at BABAR Urs Langenegger (SLAC) April 28, 23 Introduction PEP-II and detector b cl ν B D + l ν NEW Hadronic mass moments b ul ν and V ub Endpoint spectrum Hadronic recoil mass NEW

2 Motivation Test CKM description of quark mixing and CP violation Complementary constraining measurements to angles (e.g. sin 2β) Quantitatively test underlying theory ) d s = b W V ud V us V ub V cd V cs V cb V td V ts V tb ( d s b Semileptonic B-decays give direct access to V cb and V ub Factorization of hadronic and leptonic currents Inclusive large rate Γ sl B/τ V cb 2 `easy' to calculate OPE/HQE Exclusive `easy' to measure formfactors HQET, lattice Separation of b cl ν and b ul ν B( B X c l ν) 5 B( B X u l ν) M V ud V* ub α V td V* tb V cd V* V* cb γ (ρ,η) V cd β cb (,) (1,) Urs Langenegger IPHE Lausanne (April 28, 23) 1 b W _ ν l c/u

3 The PEP-II Collider on the Υ (4S)... Head-on collisions without crossing angle e (9 GeV) e + (3.1 GeV) βγ =.56 e e + _ b Y(4S) b B= B B + / d / u d _ / u _ B= B / B Parameter design achieved L [ 1 33 cm 2 s 1 ] L dt/shift [ pb 1 ] L dt/24h [ pb 1 ] # bunches HER current [A] LER current [A] σ (e + e - Hadrons)(nb) ϒ(1S) ϒ(2S) ϒ(3S) Mass (GeV/c 2 ) "OFF" "ON" ϒ(4S) Urs Langenegger IPHE Lausanne (April 28, 23) 2

4 ... a B Factory 4 Daily luminosity 12 Integrated luminosity Daily Delivered and Recorded Luminosities (pb -1 ) BABA R Integrated Luminosity (fb -1 ) BABA R PEP-II Delivered /fb BABAR Recorded /fb BABAR off-peak 9.93/fb 4 1 Jan 1 Nov Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep 1 2 Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep 1 21 Jul 1 May 1 Mar 1 Nov 1 Sep 1 22 Jan 1 May 1 Mar 1 23 Jan 1 Nov Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep 1 2 Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep 1 21 Jul 1 May 1 Mar 1 Nov 1 Sep 1 22 Jan 1 May 1 Mar 1 23 Operation efficiency ε 97%. NB: 3 5 B B events/s Urs Langenegger IPHE Lausanne (April 28, 23) 3

5 The BABAR Detector BABAR, NIM A479, 1 bla Urs Langenegger IPHE Lausanne (April 28, 23) 4

6 Electron Identification [1] Drescher et al., NIM A237, 464 [2] Sinkus, Voss, NIM A391, 36 Energy deposition E in EMC: electrons E/p 1, hadrons E mip 2 MeV shower shapes, azimuthal[1] and lateral[2]: LAT = n i=3 E ir 2 i n i=3 E ir 2 i + E 1r 2 + E 2r 2 Additional hadron rejection: DCH: de/dx (below Cherenkov threshold) DIRC: cos θ C (above Cherenkov threshold) Urs Langenegger IPHE Lausanne (April 28, 23) 5

7 Electron Identification Performance Two selectors: cut based ε 91% likelihood ratios ε 92% Efficiency determination: radiative Bhabha events in Data Hadron fakes fractions from Monte Carlo misidentification probability in Data K S π + π, τ hhh D + D ( K π + )π + s Λ pπ N fake = (f π η π +f K η K + f p η p ) N h η (cut based) η (likelihood ratios) MC-correction for shower overlaps in hadronic events Urs Langenegger IPHE Lausanne (April 28, 23) 6

8 Semileptonic B Decays Weak decay of free quark Γ(b cl ν) = G2 F V cb 2 192π 3 m5 b Improvements to free quark model EW corrections perturbative QCD corrections But: Quark mass m b? Model for b q binding? For a model-independent test want observable = (calc. factor) [ 1 + i For m Q Λ QCD Exclusive: Heavy Quark Effective Theory Inclusive: Heavy Quark Expansion (small parameter) i ] Separation of scales: Weak decay hadronization QCD b B e.g. Ligeti, hep-ph/3231 Buchalla, hep-ph/2292 Falk, hep-ph/7339 W W _ ν _ ν Urs Langenegger IPHE Lausanne (April 28, 23) 7 l c l X

9 HQET: B D l ν at zero recoil Differential decay rate (schematically) given in Heavy-Quark Effective Theory[1] by dγ( B D ( ) l ν) dw = K V cb 2 { (w 2 1) 1/2 F 2 (w) (w 2 1) 3/2 F 2 (w) _ B [1] Isgur, Wise, PLB232, 113 Isgur, Wise, PLB237, 527 W _ ν l D *+ where w v b v c v B v D = E D /m D Form factor F(w) HQET: reduction of number of form factors HQS: normalization at zero recoil: F(1) 1 valid in the limit m Q Program for V cb : Measure rate at w 1 Compute corrections to F(1) for finite m Q Zero Recoil l b _ q c _ q t < q 2 = q2 max l c ν q ν _ q 2 = q2 min Urs Langenegger IPHE Lausanne (April 28, 23) 8

10 B D + l ν Event Selection Event selection lepton with p > 1.2 GeV Electrons and muons reconstructed D + D π s D K π +, K S π+ π, K π + π π +, K π + π δm = m D π s m D Backgrounds: Uncorrelated B D + X, B Y l (D +, l) Correlated B D + X, X Y l MC Continuum off-resonance Combinatorics sideband 15 B D + Xl ν Background characterization with angle between D + and l angle between B and (D + l) both in Υ (4S) restframe Events /.5 MeV 1 5 π s D e/µ π D*-D y K Beamspot Mass Difference (MeV) x {elec;os;onres} Signal + BG Uncorrelated D*l BG Continuum D*l BG Real D*,Fake l BG Fake D* BG Urs Langenegger IPHE Lausanne (April 28, 23) 9

11 Signal extraction: cos θ B,D l At Υ (4S), well known beam parameters B meson energy and momentum magnitude For signal decay B D l ν events/ Muons D*lnu Signal 74.4 % D**lnu 7.5 % Real D*, Fake l BG 2.69 % Uncorrelated D*l BG 4.2 % Correlated D*l BG 1.78 % Continuum D*l BG 3.21 % Fake D* BG 6.31 % 2 p 2 ν = (p B p D + p l ) = p 2 B + p 2 D l 2p B p D l = m 2 B + m 2 D l 2(E B E D l p B p D l) cos θ B,D l = 2E BE D l m 2 B m2 D l 2 p B p D l events/ Electrons D*lnu Signal 73.5 % D**lnu 7.5 % Real D*, Fake l BG.3 % Uncorrelated D*l BG 6.2 % Correlated D*l BG 1.5 % Continuum D*l BG 3.2 % Fake D* BG 7.8 % If additional particle(s) missing negative tail in cos θ B,D l distribution Bremsstrahlung: electrons vs. muons cosθ B,D*l Urs Langenegger IPHE Lausanne (April 28, 23) 1

12 Preliminary Result: B( B D + l ν) Full data set of on resonance: L = 79.1 fb 1 off resonance: L = 9.6 fb 1 giving 7 signal events with purity of 7-8% Average 2(e/µ) 4(D ) 3(years) samples Preliminary result B( B D l ν) = N data N BG ε N B B(D D π s ) B( D ) B( B D + l ν) = 4.92 ±.3 stat ±.2 MC stat ±.3 syst % Completely systematics dominated Future work: V cb to come soon... Do the exclusive branching fractions add up? Urs Langenegger IPHE Lausanne (April 28, 23) 11

13 Systematics [1] Belle, PLB 526,247 [2] CLEO, PRL 89,8183 [3] OPAL, PLB 482,15 Systematics (relative error) in comparison Source BABAR BELLE[1] CLEO[2] OPAL[3] B, τ B f + /f, f Bd n/a 4.9 slow pion efficiency n/a Tracking/Vertexing D l ν Formfactors Total (Opal just as an example for an excl. LEP analysis) Differences between LEP and Υ (4S): p B 3 GeV.3 GeV background from D l ν and D Xl ν slow charged pion (tracking) dependence on formfactors (lepton spectrum) slow neutral pion (calorimetry) Urs Langenegger IPHE Lausanne (April 28, 23) 12

14 The World Average (or mirror at KEK) Scale results to set of common input parameters Correlated systematics branching fractions lifetimes B production fractions HQET parameters D modeling Difference to PDG 22! Remove results obtained with different methods (2 ARGUS) Remove superceeded results (CLEO) PDG will be updated ALEPH 5.72 ±.26 ±.37 OPAL (Incl) 6.7 ±.27 ±.59 OPAL (Excl) 5.39 ±.19 ±.41 DELPHI (incl) 4.9 ±.13 ±.35 BELLE 4.66 ±.23 ±.4 CLEO 6.24 ±.19 ±.39 DELPHI (Excl) 5.68 ±.2 ±.41 BABAR 4.89 ±.3 ±.26 Average 5.17 ±.18 HFAG Winter * - 7 B(B D l ν) [%] Urs Langenegger IPHE Lausanne (April 28, 23) 13

15 QCD in the Heavy Quark Limit Chay et al., PL B247, 399 Bigi and Uraltsev, PL B293, 43 Operator Product Expansion gives (schematically) decay rate: Γ(b cl ν) G2 F V cb 2 192π 3 m5 b [ 1 + m b + f(λ 1, λ 2 ) m 2 b α S (...) +... π ] Non-perturbative parameters Λ : interactions of light degrees of freedom with b-quark : m B = m b + Λ λ 1+3λ 2 2m b +... λ 1 : ( ) kinetic energy squared of b-quark in B-meson b λ 2 : chromo-magnetic coupling of b-quark spin to ``brown muck'' Similar expansions for other observables O = f(λ, λ 1 ; λ 2 ), e.g. moments of lepton energy and hadronic mass distributions Determinations of Λ and λ 2 : b sγ E γ = m B Λ Mass difference of B-B λ 2.12 GeV 2 γ s _ q Urs Langenegger IPHE Lausanne (April 28, 23) 14

16 Spectral Moments Measurements [1] CLEO, PRL 87, [2] CLEO, PRL 87, [3] Falk, Luke, PRD 57, 424 [4] DELPHI, hep-ex/2146 CLEO[1,2] [3] DELPHI[4] Λ =.35 ±.7 ±.1 GeV Λ =.44 ±.4 ±.5 ±.7 GeV λ 1 =.236 ±.71 ±.78 GeV 2 λ 1 =.23 ±.4 ±.5 ±.8 GeV 2 Caveat CLEO: No access to high-mass charm states as p l > 1.5 GeV/c DELPHI: Not a direct measurement Urs Langenegger IPHE Lausanne (April 28, 23) 15

17 `Recoil' Physics Fully reconstructed hadronic B-decays B D ( ) (n 1 π ± + n 2 K ± + n 3 K S + n 4 π ), n 1 + n 2 < 6, n 3 < 3, n 4 < 3 Knowledge of beam energies at the Υ (4S): m ES = E 2 beam p 2 B E = E B E beam Efficiency: B.3% B +.5% 4B/ fb 1 ) 2 Events / (2.5 MeV/c x1 P = 26% e All Events [GeV/c ] m ES B Y(4S) ) 2 Events / (2.5 MeV/c π e + Breco _ D 1 lepton, p l > 1 GeV/c 12 P = 65% N sl = 3221 K π [GeV/c ] m ES Urs Langenegger IPHE Lausanne (April 28, 23) 16

18 Hadronic Mass Moments at BABAR Goal: Measure m Xc distribution for different (low) p l cuts Access to different phase space compared to CLEO Direct measurement of m X e (3 measured parameters) Kinematic Fit Conservation of (E, p) E Breco + E X + E l + E ν e = E PEP II Y(4S) B e + X c (u) (3 measured parameters) ν (3 unmeasured parameters) p Breco + p X + p l + p ν = p PEP II Mass constraint m Breco = m Xlν Event selection: One lepton with p >.9 GeV D π K π B reco (4 measured parameters) Q l = Q B for B reco + Q 1 m 2 miss 1 GeV2 Preliminary analysis on 5 fb 1 Urs Langenegger IPHE Lausanne (April 28, 23) 17

19 Fit to m X Measure m X Distribution with as a function of p min of lepton in recoil Binned χ 2 fit to m X distribution with 3 floating contributions: D +/, D +/, X H (resonant and non-resonant components) Background component fixed Non-resonant X H contribution p min -dependent Urs Langenegger IPHE Lausanne (April 28, 23) 18

20 Determination of Moment [1] Scora et al., PRD 52, 2783 [2] CLEO, PRL 76, 3898 [3] Goity, Roberts, PRD 51, 3459 Use underlying true values for experimental determination m 2 X m 2 D = R D (M 2 D m 2 D) + R D (M 2 D m 2 D) + R XH M 2 X H m 2 D m 2 D = m D+3m D 4 = GeV/c 2 Input parameters: Channel M gen y B Model Dlν ISGW2[1] D lν HQET, FF[2] XH res lν ISGW2[1] lν GR[3] X nres H Parameters of non-resonant X H not precisely known Urs Langenegger IPHE Lausanne (April 28, 23) 19

21 Preliminary Results Strong p min dependence of moments Statistics limited, largest systematics: X H model and background For p min = 1.5 GeV/c and with Λ =.35 ±.13 GeV (from b sγ, CLEO[1]): λ 1 =.17 ±.6 ±.7 GeV 2 <M M > _ 2 2 D X OPE(Falk, _ Luke) Λ =.35 GeV [1] CLEO, PRL 87, BABAR, hep-ex/2784 BABAR Preliminary CLEO OPE(Falk, _ Luke) Λ, λ free parameters 1 BUT: These parameters do not describe p min dependence of moments..8 Rise of moment driven by high-mass charm states phase-space suppressed at p min > 1.5 GeV largest contribution from non-resonant X h Note: Data points highly correlated p * min [GeV/c] Urs Langenegger IPHE Lausanne (April 28, 23) 2

22 X H Mass Distribution Largest contribution to systematic error at low p min Estimate contribution from data: Assume PDG B for D and D Fix background BG Subtract D, D, and BG from data Resulting distribution is fully compatible with MC m XH consistent with value used in determination of first mass moment Urs Langenegger IPHE Lausanne (April 28, 23) 21

23 Analysis Strategies for B X u l ν The problem: B( B X c l ν) 5 B( B X u l ν) Exclusive V ub measurements: Experimentally: B ρl ν, B πl ν Form factors: Lattice QCD, quark models, sum rules,... Inclusive V ub measurements: Lepton energy spectrum[1]: E l > (m 2 B m2 D )/2m B Hadronic mass spectrum[2]: m X < m D Dilepton mass spectrum[3]: q 2 > (m B m D ) 2 Hadronic energy spectrum[4]: E X < m D Combinations of the above[5]: (m X, q 2 ) Restricted phase space Extrapolation: f u (E l > 2.3 GeV) 1% f u (m X < 1.55 GeV) 7% Convergence of calculation dγ/de e B (Leibovich) dγ(b c)/de e 1 dγ(b u)/de e 1 2 E e (GeV) q 2 W [1] Neubert, PR D49, 3392 Bigi et al., IJMP A9,2467 [2] Barger et al., PL B251, 629 [3] Bauer et al., PL B479, 395 [4] Greub et al., PR D56, 425 [5] Bauer et al., PR D64, 1134 Urs Langenegger IPHE Lausanne (April 28, 23) 22 _ ν l E l X E m X

24 B( B X u l ν): `Endpoint' [1] Neubert, PR D49, 3392 Bigi et al., IJMP A9,2467 [2] Voloshin, PL B515, 74 Bauer et al., hep-ph/2515 Neubert, hep-ph/272 Original method to measure charmless semileptonic B-decays Best experimental rejection of B Xc l ν Problems: Sample 1% of phase space Large model-dependence in extrapolation Solution at O(Λ QCD /m b ) [1] Fermi motion of b-quark parametrized by shape function Use photon energy spectrum in b sγ to constrain it Remove (to some extent) model-dependence from fraction f u ( p ) Importance of sub-leading effects[2]? These results not corrected with recent calculations arbitrary units lepton spectrum: b >c >xlν b >clν b > ulν "Endpoint" p* [GeV/c] Urs Langenegger IPHE Lausanne (April 28, 23) 23

25 Event Selection Analysis based on 2 fb 1 Event selection based on R 2 <.4 high-momentum electron p > 2. GeV and ν signature p miss > 1 GeV.9 < cos θ miss <.8 cos α < e + α _ ν e θ miss e Number of Tracks / 5 MeV/c 1 5 B A B A R ON Υ(4S) OFF Υ(4S) fit to continuum ON OFF Υ(4S) MC B > not ul ν B > ulν (ISGW2) Electron Momentum (GeV/c) Urs Langenegger IPHE Lausanne (April 28, 23) 24

26 Preliminary Results BABAR, hep-ex/2781 [1] CLEO, PRL 88,23183 Electron yields.1 B A B A R p [ GeV] N on 7414 ± ± 8 N off 7749 ± ± 93 N b cl ν ± ± 41 N BG 1377 ± ± 31 N b ul ν 3857 ± ± 133 db/dp (1 3 ) (GeV/c) DATA MC (ISGW2) Partial branching fraction for 2.3 < p < 2.6 GeV: Electron Momentum (GeV/c) B( B X u e ν) = (.152 ±.14 stat ±.14 syst ) 1 3 With f u (2.3 < p < 2.6) =.74 ±.14 ±.9 from CLEO[1] B( B X u l ν) = (2.5 ±.27 exp ±.46 fu ) 1 3 V ub = (4.43 ±.29 exp ±.25 OP E ±.5 fu ±.35 sγ ) 1 3 Urs Langenegger IPHE Lausanne (April 28, 23) 25

27 B( B X u l ν): hadronic recoil mass Advantages Large acceptance Good b cl ν rejection Good resolution with direct measurement Disadvantages Leading order dependence on shape function Low statistics of B reco sample Experimentally separate the two B mesons veto on K + and K S data control sample gen [GeV] lepton with p > 1 GeV/c and charge correlation to B reco well reconstructed event: m 2 miss, Q tot arbitrary units e.5 b -> c l ν measure B( B X u l ν)/b( B Xl ν) to reduce expt'l systematics M X Y(4S) B arbitrary units B reco b-> u l ν e +.5 Barger et al., PL B251, 629 Dikeman et al., NP B59, 378 Bigi et al., EPJ C4, 453 Falk et al., PL B46, 225 hybrid non-resonant gen [GeV] X e c (u) _ D M X e π + K π Urs Langenegger IPHE Lausanne (April 28, 23) 26

28 Event Selection Determination of signal and normalization samples Selection Signal Normalization B reco purity lepton momentum p > 1 GeV > 1 GeV number of leptons = 1 1 charge correlation lepton-b reco yes - missing mass m 2 miss <.5 - total charge of event Q tot = - K + and K S ( π+ π ) veto yes - Partial reco'ed B D + l ν veto yes - b cl ν background in m X < 1.55 GeV: 25% undetected K L 3% K S π π 15% missed K + Specific cuts against curlers, clone, and other bad tracks hadronic split-offs, neutral hadrons Urs Langenegger IPHE Lausanne (April 28, 23) 27

29 Fit Method Extract # signal events with fit of 3 shapes to m X distribution: B(B X u lν) B(B Xlν) = (N data N bg )/(ε u sel f u) N sl εsl l εsl t ε u l εu t arbit. norm. 5 Data b u l ν 4 b c l ν Background 3 2 ε u sel : signal efficiency f u : signal fraction with m X < 1.55 GeV ε sl t /ε u t : B reco bias ε sl l /εu l : lepton spectrum Apply corrections for background in N sl (6.8%) fake leptons cascade charm decays τ decays sideband subtraction mixing of B mesons ) 2 Events / (2.5 MeV/c 7 BABAR Preliminary 6 m < 1.55 GeV/c 5 X [GeV/c ] m ES ) 2 Events / (2.5 MeV/c BABAR Preliminary N sl = 3221 M X [GeV/c] [GeV/c ] m ES Urs Langenegger IPHE Lausanne (April 28, 23) 28

30 Preliminary Result Preliminary result B( B X u l ν) B( B Xl ν) =.197 ±.25 stat ±.1 MCstat (B( B X u l ν) = (2.14 ±.29 stat ±.25 syst ±.37 Λ,λ1 ) 1 3 ) Good consistency in subsamples Subset N u S/B R u/sl [1 4 ] m X < 1.55 GeV 167 ± ± 25 m X < 1.4 GeV 134 ± ± 25 m X < 1.7 GeV 191 ± ± 29 B tags 76 ± ± 43 B + tags 91 ± ± 3 electrons 99 ± ± 35 muons 67 ± ± 36 S/B comparable to exclusive analyses Events / Bin Events / Bin 45 BABAR 4 Preliminary Data 35 b u l ν 3 b c l ν m X m X [GeV/c BABAR Preliminary Data b u l ν [GeV/c 2 2 ] ] Urs Langenegger IPHE Lausanne (April 28, 23) 29

31 Systematics Detector and fitting Source Electron ID 1.% Kaon ID 2.3% Tracking 1.% Photons 4.7% K L 1.% B reco, m ES 3.8% B reco, tagging 4.% Binning 2.9% Total 9.8% Modeling of signal and background Source B and D decays 4.4% b ul ν decays 2.8% Hadronization 3.% Total 6.% Relative Error σ tot σ stat σ(b/d) σ(oth.exp.) σ(m b ) σ(a) cut on M X [GeV] Hadronization error evaluation: multiplicity-dependent fit non-resonant vs. hybrid signal MC ss popping All systematics reducible Urs Langenegger IPHE Lausanne (April 28, 23) 3

32 Signal Simulation [1] Scora et al., PRD 52, 2783 [2] defazio et al., JHEP 996, 17 Hybrid MC simulation ISGW2[1] for (low-mass) resonances (m X < 1.5 GeV) Nonresonant HQE calculation by de Fazio/Neubert[2] cumulative distribution function like HQE calculation (above lowest resonances) Fermi motion of b quark in B meson parametrized with a model where x = k + /Λ f(k + ) = N(1 x) a e (1+a)x Λ m B m b and λ 1 = 3Λ 2 /(1 + a) This parametrization is not unique, but motivated by constraints on the first few moments ) 2 Events / (.125 GeV/c Spectrum gen m X Total b u l ν resonant non-resonant [GeV/c s H in GeV 2 2 ] Urs Langenegger IPHE Lausanne (April 28, 23) 31

33 Theoretical Uncertainty Hadronic recoil mass m X mass of b quark (pole mass) kinetic energy of b quark depends on Reweighting of MC events to study extrapolation factor f u (m cut X ) efficiency ε u sel (m X) m b = 4.8 ±.12 GeV a = GeV2 Λ =.48 ±.12 GeV λ 1 = GeV [1] CLEO, PRL 87, m b m b m b = 4.8 GeV = 4.68 GeV = 4.92 GeV [GeV] m X Equivalent to CLEO's published values[1] without terms O(1/m 3 B ) and O(β α 2 S) Shape function parametrization not unique no error included for unknown shape (m b ) = 12 MeV instead of ``canonical'' (m b ) = 9 MeV (PDG22/CKM workshop) Combined theoretical error: 17.5% Integrated Spectrum m b = 4.8 a = cut [GeV] m X Urs Langenegger IPHE Lausanne (April 28, 23) 32

34 Extraction of V ub [1] Uraltsev et al., IJMP A14, 4641 [2] Hoang et al., PRL 82, 277 With PDG (CKM 22 workshop) formula V ub =.445 ( B(b ul ν) ps τ b ) 1/2 (1. ±.2pert ±.52 1/m 3 b ) V ub = (4.52 ±.29 stat ±.33 syst ±.4 Λ,λ1 ±.25 theo ) 1 3 B( B Xe ν) = 1.87 ±.18 ±.3% τ B = 1.68 ±.16 s, average of B and B + Negligible dependence on ``f + /f '' Last two errors indicate uncertainties due to Λ, λ 1 : extrapolation to full phase space theo: Γ(b ul ν) V ub Combination of assessment of theoretical errors by Uraltsev [1] and Hoang, et al. [2] with increased error on b quark mass of (m b ) = 9 MeV The total relative error on V ub amounts to 13.8% Urs Langenegger IPHE Lausanne (April 28, 23) 33

35 In Context This is NOT an official world average. Average of Υ (4S) measurements only. No scaling to common exp'l input parameters theoretical parameters Error bars show stat det (``uncorrelated'') total Correlated errors b cl ν modeling b ul ν modeling extrapolation b sγ vs. b ul ν Γ(b ul ν) V ub Relative error: 12% ALEPH 4.12 ±.67 ±.76 L3 5.7 ± 1. ± 1.4 DELPHI 4.7 ±.65 ±.61 OPAL 4. ±.71 ±.71 LEP Combination 4.9 ±.37 ±.56 CLEO (endpoint) 4.8 ±.22 ±.61 BABAR (endpoint) 4.43 ±.26 ±.67 2 CLEO (m - Q ) X 4.5 ±.61 ±.65 BABAR (m X ) 4.52 ±.38 ±.49 * BELLE (m X with D lν tag) 5. ±.64 ±.53 2 BELLE (m X - Q ) 3.96 ±.47 ±.52 Average 4.37 ± V ub [ 1 Urs Langenegger IPHE Lausanne (April 28, 23) 34 ]

36 The Future of V ub [1] Bauer et al., PL B479, 395 [2] Bauer et al., PR D64, 1134 [3] Leibovich et al., PR D61, 536 Aglietti et al., ph/2414 Inclusive analyses with HQE measure V ub with more methods avoid shape function dependence with high Q 2 region[1] subleading effects? combination m X -Q 2 [2] direct combinations with b sγ[3] better determinations of m b and Λ, λ 1,... projected error on V ub of 5-1% (theory limited); next updates of inclusive analyses this summer Exclusive decays B πl ν (on the recoil) with lattice QCD recoil: no background (and no statistics: O(2) events /1 fb 1 ) apart from recoil, statistics not a problem (but background... ) coverage of full phase space want/need improved and unquenched Lattice calculations projected error on V ub of (maybe) 1-2% to 5%; unquenched calculations by the end of this year? (JLC?) Urs Langenegger IPHE Lausanne (April 28, 23) 35

37 Conclusions PEP-II and BABAR are running very fine: 99 fb 1 delivered in Run 1+2, 2 fb 1 now in Run 3 Precise measurements of B( B D l ν) and V ub `Physics on the recoil' ca. 4 B/ fb 1 : statistics limited complementary systematics Now: Inclusive analyses of b cl ν and b ul ν + OPE Future: Exclusive b ul ν + Lattice Starting to take OPE/HQET a step further: b cl ν Precision measurements of parameters Λ(= m b ), λ 1,... Testing the consistency of theory hadronic mass moments,... Critical for (inclusive) precision determination of V ub b ul ν Error on V ub approaching 1% Constraints on the Unitarity Triangle Urs Langenegger IPHE Lausanne (April 28, 23) 36

38 Exclusive B ρe ν Analysis Strategy Analysis based on 5 fb 1 Two energy ranges for lepton LOLEP: 2. < E e < 2.3 GeV (b cl ν) HILEP: 2.3 < E e < 2.7 GeV (signal) ν reconstruction.8 < cos θ min < 1. cos θ miss <.9 cos θ BY < 1.1 (+ continuum) p B θ BY p miss p ν θ min p = p + p Y ρ l LOLEP HILEP Continuum suppression Event shape R 2 <.4 Neural net with 14 variables Urs Langenegger IPHE Lausanne (April 28, 23) 37

39 Fit for B ρ e + ν Binned max. likelihood fit: E = E had + E e + p ν E beam m had = m ππ(π) with p ν from missing momentum continuum shape from off-peak data, other shapes from MC Isospin and quark model relations used in fit: Γ(B ρ e + ν) = 2Γ(B + ρ e + ν) Γ(B π e + ν) = 2Γ(B + π e + ν) Γ(B + ρ e + ν) = 2Γ(B + ωe + ν) (Projections for B ρ e + ν) B(B ρ e + ν) = (3.29 ±.42 ±.47 ±.6) 1 4 B + ρ e + ν : 321 ± 4 B ρ + e + ν : 55 ± 63 Urs Langenegger IPHE Lausanne (April 28, 23) 38

40 Exclusive V ub Result Systematic error: Detector simulation: ±8% Background modeling: ± 11 1% Method, analysis, etc.: ±9% V ub = B(B ρ e + ν) Γ theo τ B τ B = ±.16 ps [1] Scora et al., PR D52, 2783 [2] Beyer, Melikhov, PL B436, 344 [3] Del Debbio, et al., PL B416, 392 [4] Ball, Braun, PR D58, 9416 [5] Ligeti, Wise, PR D53, 4937 Models used for Γ theo ISGW2[1] HQET constituent quark model UKQCD[2] Lattice QCD LCSR[3] Light cone sum rules Beyer/Melikhov[4] fully relativistic quark model Ligeti/Wise[5] HQET model, SU(3) flavor and SU(4) spin-flavor symmetry V ub = (3.64 ±.22 ± ) V ub / 1 ISGW2 Beyer/Melikhov UKQCD LCSR Ligeti/Wise Result and error: Central value: weighted average of the five FF results Error: half of the full spread of all theoretical uncertainties Urs Langenegger IPHE Lausanne (April 28, 23) 39