Precision Determination of the Cabibbo-Kobayashi-Maskawa ElementVcb

Abstract

We extract the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V(c)} and the most relevant parameters of the heavy quark expansion from data of inclusive semileptonic B decays. Our calculation includes the recently computed O(α(s)Λ(QCD)(2)/m(b)(2)) corrections and a careful estimate of the residual theoretical uncertainty. Using a recent determination of the charm quark mass, we obtain |V(cb)|=(42.21±0.78)×10(-3) and m(b)(kin)(1 GeV)=(4.553±0.020) GeV.

Status of |Vcb| and |Vub| CKM matrix elements

“…The uncertainty on the inclusive and of the exclusive determinations (from B → D * semileptonic decays) is about 2%, while the uncertainty on the determination from B → D semileptonic decays is about 5%. We observe a tension of 2.9σ between the latest FNAL/MILC lattice result [11] and the result from the latest global fit in the inclusive case [40].…”

Additional information on heavy quark parameters from charged lepton forward-backward asymmetry

“…Current state-of-the-art analysis are theoretical calculations up to O(α 2 s ) [19,20] [29] including investigations concerning subtleties due to the heavy final state quark "intrinsic-charm" [30][31][32] have lately been performed. The most recent global fit [18] uses the theoretical calculations up to 1/m 3 b and all known radiative corrections, however the fit results for the extracted |V cb | seem to be rather stable under adding higher order theoretical corrections as can be seen from older global analysis [33][34][35]. The number of new parameters at order 1/m 4,5 b proliferates, and hence these results cannot be simply implemented into the fit to experimental data.…”

“…Heavy Quark Symmetry (HQS) and Heavy Quark Expansion (HQE) have proven to be very successful in describing decays of heavy B-mesons [2][3][4][5]. Especially in the case of inclusive semi-leptonic decays there has been great effort both from experiment [6][7][8][9][10][11][12][13] and theory [14][15][16][17] to push the precision of |V cb | down to O( 2%) in the global fit [18]. The HQE is a double expansion in 1/m b and α s .…”

B→Dlνform factors at nonzero recoil and extraction of|Vcb|

“…(53) QCD (19) QED , whereas the most accurate analysis of inclusive semileptonic decays [3] gives |V cb | incl. = 0.04221(78).…”