A combined fit to B to D(*) l nu data yields R^{±0}=1.062(19) as evidence for isospin violation in Υ(4S) decays and branching fractions up to 1.6σ larger than prior averages, addressing inconsistencies in V_cb extractions.
Determination of the Form Factors for the Decay B0 -> D*- l+ nu_l and of the CKM Matrix Element |V_cb|
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abstract
We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V_{cb}| and of the parameters rho^2, R_1(1), and R_2(1), which fully characterize the form factors for the B0 -> D*- l+ nu_l decay in the framework of heavy-quark effective theory. The results, based on a selected sample of about 52,800 B0 -> D*- l+ nu_l decays, recorded by the BaBar detector, are rho2=1.157+-0.094+-0.027, R_1(1)=1.327+-0.131+-0.043, R_2(1)=0.859+-0.077+-0.021, and F(1)|V_cb|=(34.7+-0.4+-1.0)x10^-3. The first error is the statistical and the second is the systematic uncertainty. Combining these measurements with the previous BaBar measurement of the form factors, which employs a different fit technique on a partial sample of the data, we improve the statistical precision of the result, rho2=1.191+-0.048+-0.028, R_1(1)=1.429+-0.061+-0.044, R_2(1)=0.827+-0.038+-0.022, and F(1)|V_cb| = (34.4+-0.3+-1.1)x10^-3. Using lattice calculations for the axial form factor $\mathcal{F}(1)$, we extract |V_cb| =(37.4+-0.3+-1.2+1.2-1.4)x10^-3, where the third error is due to the uncertainty in F(1). We also present a measurement of the exclusive branching fraction, B = (4.69+-0.04+-0.34)%.
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representative citing papers
The unmeasured fraction of inclusive semileptonic B to charm decays is dominated by final states without D mesons, likely from baryons and Ds mesons.
The Heavy Flavour Averaging Group reports updated world averages for b-hadron, c-hadron, and tau-lepton properties including branching fractions, lifetimes, mixing, CP violation, and CKM elements.
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$\bar B\to D^{(*)}\ell\bar \nu$ Branching Ratios and Evidence for Isospin Breaking in $\Upsilon(4S)$ Decays
A combined fit to B to D(*) l nu data yields R^{±0}=1.062(19) as evidence for isospin violation in Υ(4S) decays and branching fractions up to 1.6σ larger than prior averages, addressing inconsistencies in V_cb extractions.
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Closing the knowledge gap in semileptonic $B\rightarrow X_c\ell\nu$ decays
The unmeasured fraction of inclusive semileptonic B to charm decays is dominated by final states without D mesons, likely from baryons and Ds mesons.
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Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of 2023
The Heavy Flavour Averaging Group reports updated world averages for b-hadron, c-hadron, and tau-lepton properties including branching fractions, lifetimes, mixing, CP violation, and CKM elements.