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Refining new-physics searches in B -> D tau nu decay with lattice QCD
- Publication Year :
- 2012
- Publisher :
- arXiv, 2012.
-
Abstract
- The semileptonic decay channel B -> D tau nu is sensitive to the presence of a scalar current, such as that mediated by a charged-Higgs boson. Recently the BaBar experiment reported the first observation of the exclusive semileptonic decay B -> D tau nu, finding an approximately 2-sigma disagreement with the Standard-Model prediction for the ratio R(D)=BR(B->D tau nu)/BR(B->D l nu), where l=e,mu. We compute this ratio of branching fractions using hadronic form factors computed in unquenched lattice QCD and obtain R(D) = 0.316(12)(7), where the errors are statistical and total systematic, respectively. This result is the first Standard-Model calculation of R(D) from ab initio full QCD. Its error is smaller than that of previous estimates, primarily due to the reduced uncertainty in the scalar form factor f_0(q^2). Our determination of R(D) is approximately 1-sigma higher than previous estimates and, thus, reduces the tension with experiment. We also compute R(D) in models with electrically charged scalar exchange, such as the type II two-Higgs doublet model. Once again, our result is consistent with, but approximately 1-sigma higher than, previous estimates for phenomenologically relevant values of the scalar coupling in the type II model. As a byproduct of our calculation, we also present the Standard-Model prediction for the longitudinal polarization ratio P_L (D)= 0.325(4)(3).<br />6 pages, 3 figures, 1 table. References and text added. Fig. 3 R(D) in 2HDM II corrected and conclusions modified. Standard-Model R(D) unchanged
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi...........98147cd82db6936783592873abece85f
- Full Text :
- https://doi.org/10.48550/arxiv.1206.4992