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Stato di Vub e Vcb Concezio Bozzi INFN Ferrara Babar Italia, Trieste 14 Aprile 2005

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Sommario Decadimenti semileptonici inclusivi –con charm (Vcb) –senza charm (Vub) Decadimenti semileptonici esclusivi – l, l (nuovi risultati, Moriond&CKM05) – D*l NB: ho attinto a piene mani da materiale presentato (da altri ma anche da me!) a CKM2005

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Misure inclusive

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Inclusive Decays – the Big Picture

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Semileptonic B Decays & HQE contains b- and c-quark masses, m b and m c 2 related to kinetic energy of b-quark G 2 related to chromomagnetic operator: B / B * mass splitting Darwin term ( ρ D 3 ) and spin-orbit interaction ( ρ LS 3 ) enter at 1/m b 3 = scale which separates effects from long- and short-distance dynamics r = m c /m b ; z 0 (r), d(r): phase space factors; A EW = EW corrections; A pert = pert. corrections ( s j, s k 0 ) No 1/m b term! Several HQE schemes exist; ops and coeffs are scheme dependent free-quark rate

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Inclusive b c ν Measure electron momentum spectrum and mass of hadronic system in SL decay Determine moments to allow comparison with parton- level calculations (duality assumed) Calculations exist for the following: Fit for HQE parameters and |V cb | Mass of hadronic system Lepton energy spectrum Gambino & Uraltsev (hep-ph/0401063, 0403166)

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Fit Results m X moments E moments = used, = unused in the nominal fit Red line: OPE fit Yellow band: theory errors B A B AR 2 /ndf = 20/15 B A B AR PRL 93:011803

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Fit Results Impressive agreement between data and theory identical results obtained in another renorm. scheme: Bauer, Ligeti, Luke, Manohar, Trott in hep-ph/0408002 kinetic mass scheme with μ=1 GeV Fitted values consistent with external knowledge 2 /ndf = 20/15 Uncalculated corrections to B A B AR PRL 93:011803 precision on m b = 1.5% precision on |V cb | = 2% 2% accuracy!

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Inclusive |V cb | status BaBar result compared with previous measurements: Agrees with value coming from exclusive B D * ν decays (from HFAG):

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Inclusive b u Limiting factor in CKM precision tests; known much less well than |V cb | CKM suppressed – therefore harder to measure Challenge for experiment and theory

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Starting point: HQE Just like b c ν …, and with similar accuracy …until limited exptl acceptance is considered Poor convergence of OPE in region where b c ν decays are kinematically forbidden Non-perturbative Shape Function must be used to calculate partial rates = scale which separates effects from long- and short-distance dynamics A EW = EW corrections; A pert = pert. corrections ( s j, s k 0 )

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Theory input Reference (ICHEP04, HFAG) results based on triple differential decay rate ( E e, m X, q 2 ) computed to O( s, m b -2 ) over the entire phase space by de Fazio and Neubert (DFN, JHEP 06:17 (1999) ) Use as input the shape function parameters determined by a fit (hep-ex/0407052) to the Belle bs spectrum: Λ = 0.66 GeV, λ 1 = -0.40 GeV 2 + covariance δ Λ ~ δm b 80 MeV q 2 vs m X analysis: take acceptances from Bauer, Ligeti and Luke (BLL, hep-ph/0111387 ), OPE calculation in a region of the phase space where SF effects are small. f(k+)f(k+) Acceptance in b uv E spectrum in b s

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Inclusive V ub measurements with BaBar methodS/B Pros&Cons V ub (x10 -3 ) Electron spectrum endpoint E e >2.0GeV Total rate using DeFazio-Neubert 0.05 0.2 High statistics Duality valid for tight E e cuts? Bkg subtraction E e vs q 2 and neutrino reconstruction E e >2.0GeV and s h <3.5 GeV 2 /c 4 Total rate using DeFazio-Neubert ~0.5 High statistics Lower syst. on shape functions Bkg subtraction m X analysis (1-D) m X <1.55 GeV/c 2 Total rate using DeFazio-Neubert ~1.7 Low background High resolution Low statistics Shape func. syst. m X vs q 2 analysis m X 8.0 GeV 2 /c 4 V ub using Bauer et al. ~2 Low background Very small syst. on SF param. Small statistics Total rate using Form Factors calc. 1 20 Very small bkg ~no cut on kinem Small statistics Untagged Untagged Partial Tags Breco Tags exclusive Current Vub errors: 10-15% Total experimental syst @250-500 ifb: 3-6% 4.40 ± 0.24 exp ± 0.35 theo 4.99 ± 0.48 exp ± 0.29 theo 5.22 ± 0.43 exp ± 0.33 theo 5.18 ± 0.57 exp ± 0.34 theo

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V ub measurements

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A different theory approach Bosch, Lange, Neubert and Paz (BLNP) Nucl. Phys. B 699, 335 (2004) Acceptances computed in BLNP using SF parameters from –Belle bs hep-ex/0407052 –BaBar bc moments (hadronic and leptonic) hep-ex/0404017 Proper translation into shape function scheme of BLNP hep-ph/0412241 Courtesy of Henning Flächer

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Results with BLNP and BaBar bc moments Using m b = 4.63±0.08 GeV and μ π 2 = 0.15±0.07 GeV 2 (SF scheme) with correlation coefficient -0.4. Errors are: expt ± SF ± theory expt ± (SF+theory) MethodB × 10 4 |V ub | (BLNP) SF params from b c ν |V ub | (BLNP) (Belle SF) |V ub | ICHEP (DFN, Belle SF) Endpoint5.31±0.59 3.93 ± 0.34 ± 0.38 ± 0.18 (8.7 ± 9.7 ± 4.6)% 4.55 4.40 ± 0.24 ± 0.35 ( ± 6.4 ± 8.6) % q 2 -E e 4.46±0.933.89 ± 0.40 ± 0.45 ± 0.21 (10.3 ±11.5 ± 5.4)% 4.53 4.99 ± 0.48 ± 0.29 ( ± 9.6 ± 5.8) % q 2 -m x 8.96±2.044.45 ± 0.49 ± 0.40 ± 0.22 (11.1 ± 9.0 ± 4.9)% 5.00 5.18 ± 0.57 ± 0.34 ( ±11.0 ± 6.5) % Average4.07 ± 0.514.61 ± 0.46 bc moments: significant change in inclusive | V ub | values BLNP: increased sensitivity to SF

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Misure di Vub esclusive

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Exclusive B X u l Decays Goal : Measure Branching Fractions and |V ub | Need FF predictions to describe QCD effects New unquenched LQCD calculations (HPQCD04, FNAL04) Try to measure q 2 dependence of FF with data Breco Tags Semilep.Tags Untagged l-l- Y(4S) X u = +, 0, +, 0,, a 0 0, a 0 + low bkg, low stat.: 27,… (ICHEP04) Balance between efficiency and purity High statistics, high hackground (b cl ) 3 new l results

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Semileptonic Tag Analyses Reconstruct B D ( * ) l and study semileptonic recoil use both D and D* tags sizable BF Tagging efficiency measured with Double Tags (two D ( * ) l ) Correct sl. decay |cos BY | < 1 ( tag side: cos BY, signal side: cos B, l ) cos 2 B < 1 for signal, bkg flat D ( * ) l decays

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 0 l with SL Tag : Signal Extraction Cut-and-count analysis in cos B, l and m D Signal region: -1.1 < cos B l < 1.0 Subtract m D sidebands remove cominatoric background Subtract other background using MC normalized in -10 < cos B l < -1.5 82 fb -1 45 0

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 + l with SL Tag : Signal Extraction Extract signal yields by binned fit to cos 2 B in 3 bins of q 2 : Fit parameters = signal and background normalizations 211 fb -1 21 + 26 + 14 + 30% l X-feed Mainly B 0 B 0 bkg

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 + l with SL Tag : Branching Fractions and q SL tag analyses statistically limited. Yields not yet large enough to discriminate between FF models.

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Neutrino Reconstruction: Reconstruct from full event & ensure good reco. quality Untagged B l and B l Fit all 4 signal modes simultaneously ( +, 0, +, 0 ) Use isospin relations to reduce number of signal parameters: (B 0 - l + ) = 2 (B + 0 l + ) Max-LH fit of signal and background in E, m ES, and q 2 Harsh suppression of b cl bkg (kinem. cuts, mainly for l ) e + e - qq bkg (topological cuts) Cut on missing mass: |M 2 miss / 2E miss | < 0.4 GeV

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Untagged l : Fitted E and m ES 76 fb -1 427, 147 0 5 bins for l 3 bins for l

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Untagged l : Fitted E and m ES 5 bins for l 3 bins for l 101, 104 0 76 fb -1

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Recent LQCD and LCSR calculations agree well with data ISGW2 shows marginal agreement for l Errors for l still too large to study 3 form factors. Measured q 2 Distributions and Form Factors ll

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Systematic Uncertainties (Untagged) Better statistical precision than previous measurements Syst. error dominated by reconstruction. Will decrease with improved track/neutral reconstruction. Results less dependent on theoretical predictions (own FF measurement)

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Overview: Branching Fraction Measurements Testing isospin symmetry: Measure + l, 0 l separately (untagged) ll

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Jochen Dingfelder – CKM Workshop 2005 03/16/05 Extraction of | V ub | Measurement in bins of q 2 allows extraction of |V ub | for various q 2 regimes and FF calculations : LCSR q 2 15 GeV 2 or extrapolation to whole q 2 range Quote LQCD2 as representative

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Misure di Vcb esclusive

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Ultimate solution: combined measurement of form factors and Vcb! (work in progress in Trieste)

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Other ideas? D* 0 l (little/undermanned efforts) Yet another measurement of D* + l –D* partial reconstruction –On the recoil of a fully reconstructed hadronic decay Run1-4 M. Andreotti PhD thesis

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Conclusioni Mole impressionante di risultati sperimentali e teorici Collaborazione virtuosa tra le due comunità Effetto complessivo: –Vcb inclusivo: ~1.5% Accordo impressionante teoria-esperimenti! –Vub inclusivo: 10% 5% ? Aggiornare misure con tutta la statistica disponibile Ampio consenso teorico sulla validità delle relazioni bcν bs buν Un po meno sulle incertezze relative –Vub esclusivo: Occorre più statistica e migliorare le sistematiche sperimentali calcolo dei fattori di forma non ancora pienamente maturo –Vcb esclusivo: 4% ? Nuove misure (Dl ) per limitare incertezze teoriche e per risolvere laccordo marginale tra le misure esistenti (D*l )

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