Refining new-physics searches in BâDτν with lattice QCD.
Phys Rev Lett
; 109(7): 071802, 2012 Aug 17.
Article
em En
| MEDLINE
| ID: mdl-23006357
ABSTRACT
The semileptonic decay channel BâDτν 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 BâDτ(-)ν, finding an approximately 2σ disagreement with the standard-model prediction for the ratio R(D)=BR(BâDτν)/BR(BâDâν), where â = e,µ. 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 1σ 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 1σ higher than, previous estimates for phenomenologically relevant values of the scalar coupling in the type-II model. As a by-product of our calculation, we also present the standard-model prediction for the longitudinal-polarization ratio P(L)(D)=0.325(4)(3).
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01-internacional
Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
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Qualitative_research
Idioma:
En
Revista:
Phys Rev Lett
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Coréia do Sul