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Determination of |Vcb|, mb and mc from Inclusive B Decay Distributions

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Presentation on theme: "Determination of |Vcb|, mb and mc from Inclusive B Decay Distributions"— Presentation transcript:

1 Determination of |Vcb|, mb and mc from Inclusive B Decay Distributions
Henning Flächer Royal Holloway, University of London 13 Dec 2006 CKM Workshop 2006, Nagoya

2 Overview Will cover results of a fit to lepton, hadron and photon moments using calculations in kinetic scheme and discuss some applications (Phys. Rev. D 73, (2006)) Motivation Short Introduction to theoretical framework Experimental Measurements hadron and lepton moments from B → Xc lv photon energy moments from B → Xs γ Results of the combined fit Extraction of |Vcb|, mb, mc and higher order heavy quark parameters Applications and prospects for improving on current status Conclusions 13 Dec 2006 CKM Workshop 2006, Nagoya

3 Heavy Quark Expansions
The Operator Product Expansion separates perturbative from non-perturbative scales in a systematic way: Benson, Bigi, Mannel & Uraltsev, hep-ph/ Gambino & Uraltsev, Eur.Phys.J. C34, 181 (2004) chromomagnetic expec. value kinetic expec. value Darwin term spin-orbit kinetic scheme Need to determine non-pert. parameters! Use moments of inclusive distributions where same parameters appear: drop full OPE formula for G_SL, put after bsg mb and μπ2 are used to parameterise both B→Xs γ and B→X lv spectra El>Ecut Hadronic Mass distribution Lepton Energy spectrum Photon Energy spectrum 13 Dec 2006 CKM Workshop 2006, Nagoya

4 Lepton Energy Moments Vcb BABAR Y(4S) frame 13 Dec 2006
CKM Workshop 2006, Nagoya

5 Delphi and CDF only measure higher resonances
Hadronic Mass Moments BaBar, Belle and CLEO measure full spectrum Delphi and CDF only measure higher resonances BABAR p* > 0.9 GeV p* > 1.6 GeV MX CLEO 13 Dec 2006 CKM Workshop 2006, Nagoya

6 b→sγ Spectra and Moments
Measure photon spectrum in b→sγ decays: Two main approaches: Inclusive: identify photon Semi-Inclusive: reconstruct many exclusive final states (up to 38!) CLEO Belle Babar semi-incl. Babar fully-incl. Difficult measurement: Overwhelming background from π0s for Eγ < 1.8 GeV make moment plot smaller, then intro moment fit -> also used for bsg average (extrapol) Measurement of photon spectrum and its moments gives information about inner structure of B meson: b quark mass Fermi momentum 13 Dec 2006 CKM Workshop 2006, Nagoya

7 Available moment measurements
Legend: n = order of (central) moment of observable MX, El and Eγ l = min. lepton momentum γ = min. photon energy published with covariance matrix and used in fit not used in fit Hadron Moments Lepton Moments Photon BaBar n=1,2,3,4 l= n=0,1,2,3 l= n=1,2,3 γ= Belle n= 1,2 n=1,2 γ=1.8 CLEO n=2,4 l= γ=2.0 Delphi n=2,4,6 l=0.0 n= 1,2,3 CDF l=0.7 Total of 51 measurements! Important to take correlations between moments with different min. lepton/photon energies into account 13 Dec 2006 CKM Workshop 2006, Nagoya

8 Inclusive |Vcb| - Fit to Moments
Benson, Bigi, Mannel & Uraltsev, hep-ph/ Gambino & Uraltsev, hep-ph/ Benson, Bigi & Uraltsev, hep-ph/ Based on calculations in kinetic scheme: Lepton Moments Hadron Moments Lepton Moments Ecut (GeV) Photon Moments move after bsg Measurements highly correlated! O. Buchmueller,H.F. hep-ph/ 13 Dec 2006 CKM Workshop 2006, Nagoya

9 Inclusive |Vcb| χ2= Result of fit to all 19.3/44dof
exp HQE ΓSL χ2= 19.3/44dof Result of fit to all moment measurements: |Vcb| = (41.96 ± 0.23 ± 0.35 ± 0.59) 10-3 mb = 4.590 ± 0.025 ± 0.030 GeV mc = 1.142 ± 0.037 ± 0.045 μπ2 = 0.401 ± 0.019 ± 0.035 GeV2 μG2 = 0.297 ± 0.024 ± 0.046 ρD3 = 0.174 ± 0.009 ± 0.022 GeV3 ρLS3 = -0.183 ± 0.054 ± 0.071 BRclv = 10.71 ± 0.10 ± 0.08 % 2% mb < 1% 5% hep-ph/ In MS scheme: mb(mb) = 4.20 ± 0.04 GeV mc(mc) = 1.24 ± 0.07 GeV mc(μ)/mb(μ)= ± 0.012 courtesy of N.Uraltsev b→sγ b→clν combined move after bsg Good agreement with other similar analyses: Bauer et al. hep-ph/ DELPHI hep-ex/ Belle hep-ex/ 13 Dec 2006 CKM Workshop 2006, Nagoya

10 Treatment of Theory Errors
Construct combined experimental and theoretical covariance matrix Ctot = Cstat + Csyst + Ctheo Uncertainties in moment expansions to evaluate perturbative uncertainties on Wilson coefficients vary 2nd order terms by 20% 3rd order terms by 30% also assume 20 MeV uncertainty on mb and mc in corresponding terms additional uncertainties for Eγ moments due to higher Ecut vary αs around 0.22 ± 0.04 for lepton and 0.3 ± 0.1 for hadron moments errors considered fully correlated for varying Ecut and uncorrelated between moments of different order Uncertainties in ΓSL (hep-ph/ ) pert. uncertainty in Wilson coefficient of leading bb operator - 0.5% pert. corrections to Wilson coefficients of chromomagnetic and Darwin operators - 1.2% non-perturbative soft charm effects (hep-ph/ ) % higher order power suppressed contributions - 0.4% “Fixed” uncertainty of 1.4% - not included in fit αs uncertainty Use “best value” for ΓSL (αs = 0.22 ± 0.01) 13 Dec 2006 CKM Workshop 2006, Nagoya

11 Comparison with other determinations
mb(mb) = 4.20 ± 0.04 GeV mc(mc) = 1.24 ± 0.07 GeV Conversion from kinetic mass scheme to MS scheme with hep-ph/ , hep-ph/ See also report from CKM WS hep-ph/ 13 Dec 2006 CKM Workshop 2006, Nagoya

12 B→Xsγ Branching Fraction Average
Photon Energy Spectrum constraint with mb and μπ2 Extrapolation Factors for BF Partial branching fractions are measured above different photon energies Need to be extrapolated to Eγ > 1.6 GeV to compare with theory Extrapolation factors based on HQE fit to b→clv and b→sγ moments hep-ph/ kinetic SF KN Average label Rcut plot, don’t show all columns, only reported + Emin, units 10-6!! , only 2 numbers in 2HDM, drop 2005 To obtain spectra in other schemes: predict 1st and 2nd Eγ moment at Ecut = 1.6GeV based on result of fit in kinetic scheme. Then fit the moments in the new schemes → good agreement between calculations if comparing on basis of moments Use consistent extrapolation factors for all measurements 13 Dec 2006 CKM Workshop 2006, Nagoya

13 BR(B ® Xsg) Average involves Eg extrapolation!
SM Prediction (NLO) 3.57 ± 0.30 x10-4 Nucl.Phys.B631: ,2002 NNLO: M.Misiak et al,hep-ph/ BR(B→Xsγ)Eγ>1.6 GeV = (3.15 ± 0.23) x 10-4 NNLO NNLO: Becher & Neubert, hep-ph/ BR(B→Xsγ)Eγ>1.6 GeV = (2.98 ± 0.26) x 10-4 CLEO PRL 87, (2001) BELLE Phys.Lett. B 511, 151 (2001) BELLE PRL.93:061803,(2004) BABAR PRD 72, (2005) BABAR PRL 97, (2006) Two NNLO calculations 1.2 and 1.4 σ below World Average 7 – 9% uncertainty for both theory and experiment HFAG Average 3.55 ± 0.26 x10-4 involves Eg extrapolation! BR(B→Xsγ)Eγ>1.6 GeV x10-4 13 Dec 2006 CKM Workshop 2006, Nagoya

14 Prospects for the Future
Include Belle measurements (see previous talk by P. Urquijo) Additional Experimental Measurements possibly measure higher order moments → higher sensitivity to higher order parameters Recent effort to calculate 1/mb4 terms in SL rate Mannel et al (hep-ph/ ) fourth central moment in MX2 is dominated by fourth order terms enough experimental sensitivity? Measure “modified moments” Nx2 = Mx2 –2ΛEx + Λ Λ~500MeV under better theoretical control, leading to reduction in theory errors Measure q2 moments in B→Xc lv will constrain - or measure – non-perturbative soft charm effects (“intrinsic charm”) helps in reducing theory uncertainty on |Vcb| Revisit theory uncertainties perturbative uncertainties of Wilson Coefficients 20% and 30% variations of 2nd and 3rd order terms 13 Dec 2006 CKM Workshop 2006, Nagoya

15 Conclusions Consistency for moment measurements between experiments
Good agreement of results from semileptonic and radiative B decays Precison measurements of SM parameters: |Vcb| at 2% level Helping to reduce uncertainty on |Vub| to ~7% probing consistency with sin(2β) and hence SM mb (<1%) and mc (5%) limited by theory uncertainties in many cases Radiative B decays Consistent extrapolation for all experimental measurements BR(B→Xs 7% important constraint on many NP models 13 Dec 2006 CKM Workshop 2006, Nagoya

16 Backup Slides 13 Dec 2006 CKM Workshop 2006, Nagoya

17 Inclusive |Vcb| - Fit to Moments
Benson, Bigi, Mannel & Uraltsev, hep-ph/ Gambino & Uraltsev, hep-ph/ Benson, Bigi & Uraltsev, hep-ph/ Based on calculations in kinetic scheme: Lepton Moments Hadron Moments Ecut (GeV) Photon Moments move after bsg Measurements highly correlated! O. Buchmueller,H.F. hep-ph/ 13 Dec 2006 CKM Workshop 2006, Nagoya

18 reduced theory error as no extrapolation
Inclusive |Vub| hep-ex/ Measurement of hadronic mass spectrum in B->Xu lv decays: Measure hadronic mass spectum on the recoil of fully reconstructed B mesons Measurement of spectrum up to 2.5 GeV includes 96% of total rate Standard local OPE for full rate: Uraltsev hep-ph/ Hoang,Ligeti, Manohar hep-ph/ reduced theory error as no extrapolation to full rate necessary modify formula (Jochen) -> just mention weight function OPE: MX < 2.50 GeV: |Vub| = (3.84 ± 0.70stat ± 0.30syst ± 0.10theo) 10-3 13 Dec 2006 CKM Workshop 2006, Nagoya

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