Extraction of |Vcb| from B → D(∗)ℓνℓ and the Standard Model predictions of R(D(∗))

Abstract

We extract |V cb | from the available data in the decay B → D ( * ) ν . B → D * ν , the unfolded binned differential decay rates of four kinematic variables including the q 2 bins have been used. In the CLN and BGL parameterizations of the form factors, the combined fit to all the available data along with their correlations yields |V cb | = (39.77 ± 0.89) × 10 −3 and (40.90 ± 0.94) × 10 −3 respectively. In these fits, we have used the inputs from lattice and light cone sum rule (LCSR) along with the data. Using our fit results and the HQET relations (with the known corrections included) amongst the form factors, and parameterizing the unknown higher order corrections (in the ratios of HQET form factors) with a conservative estimate of the normalizing parameters, we obtain R(D * ) = 0.259 ± 0.006 (CLN) and R(D * ) = 0.257 ± 0.005 (BGL).

Precision model-independent bounds from a global analysis of b→cℓν form factors

“…Measurements from BaBar, Belle, and LHCb of the ratios R(D ( * ) ) [10][11][12][13][14][15][16][17][18][19] of the heavy-light meson decays B → D ( * ) ν, with = τ to = µ, exhibit a combined 3.1σ discrepancy from the HFLAV-suggested [20], which average Refs. [6,[21][22][23]. Recently, the LHCb collaboration has measured R(J/ψ) [24], which is within 1.3σ [25] of the SM prediction.…”

“…The constraint of unitarity in model-independent approaches such as the BGL parametrization has historically been underutilized, because fits to experiment typically consider only a single exclusive process (e.g., B → D * ν). However, each exclusive channel appearing in the two-point Green's function for b → c currents positively contributes to the unitarity bound, and therefore a simultaneous fit including multiple processes provides stronger constraints on each of the individual processes [6,23,37].…”

Updated Bs -mixing constraints on new physics models for b→sℓ+ℓLuzio1, Kirk2, Lenz3 2018Phys. Rev. D13171631View full textAdd to dashboardCite

“…Recent studies found, however, that the low exclusive value might actually be a problem originating in the use of a certain form factor parametrization in the experimental analysis. 8 Using the Boyd, Grinstein, Lebed (BGL) parametrization one finds values that lie considerably closer to the inclusive one, see [143][144][145][146]. Currently, there are various determinations of V cb available: …”

Measurement of R(D) and R(D*) wi

“…Hereafter,B → D ( * ) τ −ν τ [4] and B → D ( * ) −ν will be referred to as the signal and normalization modes, respectively. The SM calculations for these ratios, performed by several groups [5][6][7][8], are averaged by HFLAV [9] to obtain R(D) = 0.299 ± 0.003 and R(D * ) = 0.258 ± 0.005. Semitauonic B decays were first observed by Belle in 2007 [10], with subsequent studies reported by Belle [11][12][13][14], BaBar [15], and LHCb [16,17].…”