This web page contains the averages of the ratios of Branching Fractions
R(D*)=BF(B→D*τν_{τ})/BF(B→D* l ν_{l})
and R(D)=BF(B→Dτν_{τ})/BF(B→D l ν_{l}).
In the present average we consider the following measurements:
Experiment | R(D*) | R(D) | Rescaled Correlation (stat/syst/total) | Inputs | Remarks |
---|---|---|---|---|---|
BaBar | 0.332 ± 0.024 ± 0.018 | 0.440 ± 0.058 ± 0.042 | -0.45/-0.07/-0.27 | input | Phys.Rev.Lett. 109,101802 (2012) arXiv:1205.5442_[hep-ex] Phys.Rev.D 88, 072012 (2013) arXiv:1303.0571_[hep-ex] |
BELLE | 0.293 ± 0.038 ± 0.015 | 0.375 ± 0.064 ± 0.026 | -0.56/-0.11/-0.49 | input | Phys.Rev.D 92, 072014 (2015) arXiv:1507.03233 [hep-ex] |
LHCb | 0.336 ± 0.027 ± 0.030 | - | - | input | Phys.Rev.Lett.115,111803 (2015) arXiv:1506.08614 [hep-ex] |
BELLE | 0.270 ± 0.035 ^{+ 0.028}_{-0.025} | - | - | input | Phys.Rev.Lett.118,211801 (2017) arXiv:1612.00529 [hep-ex] Phys.Rev.D 97, 012004 (2018) arXiv:1709.00129_[hep-ex] |
LHCb | 0.283 ± 0.019 ± 0.029 | - | - | input | Phys.Rev.Lett.120,171802 (2018) arXiv:1708.08856_[hep-ex] Phys.Rev.D 97, 072013 (2018) arXiv:1709.02505_[hep-ex] |
BELLE | 0.283 ± 0.018 ± 0.014 | 0.307 ± 0.037 ± 0.016 | -0.53/-0.51/-0.51 | input | Phys.Rev.Lett. 124 (2020) 16, 161803 arXiv:1910.05864 [hep-ex] |
LHCb | 0.281 ± 0.018 ± 0.024 | 0.441 ± 0.060 ± 0.066 | -0.49/ /-0.43 | input | LHC Seminar, 18 Oct 2022 [CERN LHC Seminar] |
Average .txt | 0.291 ± 0.014 | 0.351 ± 0.029 | -0.41 | chi2/dof = 9.21/8 (CL = 0.37) |
R(D)-R(D*).pdf
(dashed curves correspond to 3 σ contour)
R(D) .pdf .png R(D*) .pdf .png |
SM predictions for R(D) based on following Lattice calculations:
The SM prediction for R(D^{*}) widely used in previous HFLAV averages was:
The BaBar collaboration computed an indipendent prediction of R(D^{*})=0.253 ± 0.005, from a full angular analysis of B→D^{*}l ν Phys.Rev.Lett. 123 (2019) 9, 091801.
Recently, FNAL/MILC released the first unquenched Lattice calculation of B→D^{*}l ν form factors at non-zero recoil, A.Bazavov et al. [arXiv:2105.14019 [hep-lat]] , predicting a value of R(D^{*})=0.265 ± 0.013, using only Lattice inputs. A combined analysis with experimental inputs of both B→Dl ν and B→D^{*}l ν would be desirable.
These new calculations are in good agreement between each other, and consistent with old predictions for R(D^{*}), but more robust.
The central values of the SM predictions, and their uncertainty estimates, will evolve as more precise measurements of B→D(^{*})l ν spectra and new calculations become available.
The disagreement on the treatment of the theoretical uncertaitines can be settled when further calculations
of the B→D^{*} Form Factors beyond the zero recoil limit as well as information on the pseudoscalar Form Factor will be available.
R(D) | R(D^{*}) | |
---|---|---|
D.Bigi, P.Gambino, Phys.Rev. D94 (2016) no.9, 094008 [arXiv:1606.08030 [hep-ph]] | 0.299 ± 0.003 | |
P.Gambino, M.Jung, S.Schacht, Phys.Lett.B795 (2019) 386 [arXiv:1905.08209 [hep-ph]] | 0.254 + 0.007 − 0.006 | |
M.Bordone, M.Jung, Danny van Dyk, Eur.Phy.J.C 80 (2020) 2, 74 [arXiv:1908.09398 [hep-ph]] | 0.298 ± 0.003 | 0.247 ± 0.006 |
F.Bernlochner, Z.Ligeti, M.Papucci, D.Robinson, Phys.Rev. D95 (2017) no.11, 115008 [arXiv:1703.05330 [hep-ph]] | 0.299 ± 0.003 | 0.257 ± 0.003 |
S.Jaiswal, S.Nandi, S.K.Patra, JHEP 1712 (2017) 060 [arXiv:1707.09977 [hep-ph]] | 0.299 ± 0.004 | 0.257 ± 0.005 |
BaBar Collaboration, Phys.Rev.Lett. 123 (2019) 9, 091801 [arXiv:1903.10002 [hep-ex]] | 0.253 ± 0.005 | |
G. Martinelli, S. Simula, L. Vittorio, Phys.RevD 105 (2022) 3, 034503 [arXiv:2105.08674 [hep-ph]] | 0.296 ± 0.008 | |
Arithmetic average | 0.298 ± 0.004 | 0.254 ± 0.005 |
D.Bigi, P.Gambino, S.Schacht, JHEP 1711 (2017) 061 [arXiv:1707.09509 [hep-ph]] | 0.260 ± 0.008 | |
M.Bordone, M.Jung, Danny van Dyk, Eur.Phy.J.C 80 (2020) 2, 74 [arXiv:1908.09398 [hep-ph]] | 0.297 ± 0.003 | 0.250 ± 0.003 |
FNAL/MILC, A.Bazavov et al. [arXiv:2105.14019 [hep-lat]] | 0.265 ± 0.013 |
R(D) and R(D^{*}) exceed the SM predictions given above, by 1.82σ and 2.49σ respectively.
Considering the R(D)-R(D^{*})) correlation of -0.41, the resulting combined χ^{2} is 15.2 for 2 degree of freedom,
corresponding to a p-value of 0.46 x 10^{-3}. The difference with the SM predictions reported above, corresponds to about 3.5σ.