Model-independent extraction of form factors and |V_cb| in B → D ℓ^- ν_ℓ with hadronic tagging at BaBar

2023/11/25 by BaBar Collaboration, Lees, J. P., Poireau, V. +208
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2311.15071

Abstract

Using the entire BaBar Υ(4S) data set, the first two-dimensional unbinned angular analysis of the semileptonic decay B → D ℓ^- ν_ℓ is performed, employing hadronic reconstruction of the tag-side B meson from Υ(4S)→ BB. Here, ℓ denotes the light charged leptons e and μ. A novel data-driven signal-background separation procedure with minimal dependence on simulation is developed. This procedure preserves all multi-dimensional correlations present in the data. The expected sin²θ_ℓ dependence of the differential decay rate in the Standard Model is demonstrated, where θ_ℓ is the lepton helicity angle. Including input from the latest lattice QCD calculations and previously available experimental data, the underlying form factors are extracted using both model-independent (BGL) and dependent (CLN) methods. Comparisons with lattice calculations show flavor SU(3) symmetry to be a good approximation in the B_(s)→ D_(s) sector. Using the BGL results, the CKM matrix element |V_cb|=(41.09± 1.16)× 10^-3 and the Standard Model prediction of the lepton-flavor universality violation variable R(D)=0.300± 0.004, are extracted. The value of |V_cb| from B → D ℓ^- ν_ℓ tends to be higher than that extracted using B → D ℓ^- ν_ℓ. The Standard Model R(D) calculation is at a 1.97σ tension with the latest HFLAV experimental average.

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