The semileptonic decay width is calculated in the framework of the operator production expansion (OPE), which results is a double-expansion in Lambda_QCD/m_b and alpha_S. Depending on the expansion order in mb and other choices, this calculation contains a certain number of (non-calculable) non-perturbative parameters. These are determined from other inclusive observables in B -> Xclnu, such as the moments of the El, MX and q2=(pl+pnu)2 distributions.
Measurements of B -> Xclnu moments are obtained by:
| Analysis | Br(B -> Xclnu) (%) | |Vcb| (10-3) | Reference |
|---|---|---|---|
| El and MX moments | 10.66 +/- 0.15 | 42.16 +/- 0.30(th) +/- 0.32(exp) +/- 0.25(th_width) | Phys.Lett.B 822 (2021) 136679 |
| q2 moments | 10.48 +/- 0.13 (external input) | 42.69 +/- 0.63 | JHEP 10 (2022) 068 |
| El, MX and q2 moments | 10.63 +/- 0.15 | 41.97 +/- 0.27(th) +/- 0.31(exp) +/- 0.25(th_width) | JHEP 02 (2024) 206 |
Due to the unknown correlations between these analyses we refrain from averaging the results for Br(B -> Xclnu) and |Vcb|. Instead we use the result of JHEP 02 (2024) 206 as our central value.