Article

# Semileptonic form factors D \rightarrow \pi, K and B \rightarrow \pi, K from a fine lattice

ETH Zürich Institute for Theoretical Physics 8093 Zürich Switzerland; Deutsches Elektronen-Synchrotron DESY 22603 Hamburg Germany
European Physical Journal A (Impact Factor: 2.42). 01/2009; 43(1). DOI: 10.1140/epja/i2009-10893-3
Source: arXiv

ABSTRACT We extract the form factors relevant for semileptonic decays of D and B mesons from a relativistic computation on a fine lattice in the quenched approximation. The lattice spacing is a = 0.04 fm (corresponding to a
-1 = 4.97 GeV), which allows us to run very close to the physical B meson mass, and to reduce the systematic errors associated with the extrapolation in terms of a heavy-quark expansion. For decays of D and Ds mesons, our results for the physical form factors at

$\ensuremath q^2 = 0$
are as follows:

$\ensuremath f_+^{D\rightarrow\pi}(0) = 0.74(6)(4)$
,

$\ensuremath f_+^{D \rightarrow K}(0) = 0.78(5)(4)$
and

$\ensuremath f_+^{D_s \rightarrow K} (0) = 0.68(4)(3)$
. Similarly, for B and Bs we find

$\ensuremath f_+^{B\rightarrow\pi}(0) = 0.27(7)(5)$
,

$\ensuremath f_+^{B\rightarrow K} (0) = 0.32(6)(6)$
and

$\ensuremath f_+^{B_s\rightarrow K}(0) = 0.23(5)(4)$
. We compare our results with other quenched and unquenched lattice calculations, as well as with light-cone sum rule predictions, finding good agreement.

1 Bookmark
·
170 Views
• Source
##### Article: HADRONIC FORM FACTORS: COMBINING QCD CALCULATIONS WITH ANALYTICITY
[Hide abstract]
ABSTRACT: I discuss recent applications of QCD light-cone sum rules to various form factors of pseudoscalar mesons. In this approach both soft and hard contributions to the form factors are taken into account. Combining QCD calculation with the analyticity of the form factors, one enlarges the region of accessible momentum transfers.
International Journal of Modern Physics A 01/2012; 25(02n03). · 1.09 Impact Factor
• ##### Article: Exclusive b→sℓ+ℓ−b→sℓ+ℓ− decays
[Hide abstract]
ABSTRACT: The experimental progress on flavor-changing neutral current decays governed by b→sℓ+ℓ−b→sℓ+ℓ− transitions has grown enormously due to the latest results of BaBar, Belle, CDF and LHCb. Especially the exclusive modes B→K(⁎)ℓ+ℓ−B→K(⁎)ℓ+ℓ−, which have the largest rates, provide a variety of observables which constrain non-standard interactions that would affect them beyond the Standard Model. The theoretical treatment, based on expansions in ΛQCD/mbΛQCD/mb, focuses on low- and high dilepton invariant mass regions. Notably, form factor symmetries guided the identification of optimized observables in both regions which have small form factor dependences and sensitivity to new physics. Current experimental results of rates and lepton forward-backward asymmetries allow for first global analysis of b→sℓ+ℓ−b→sℓ+ℓ− decays in combination with b→sγb→sγ and Bs→μ+μ−Bs→μ+μ−. These analyses are now ready to be applied to include high-statistics results from LHCb and Super-Flavor factories within the next years and to profit from optimized observables.
Nuclear Physics B - Proceedings Supplements 12/2012; 233:139–144. · 0.88 Impact Factor
• Source
##### Article: Rare decay B→Kℓ^{+}ℓ^{-} form factors from lattice QCD
[Hide abstract]
ABSTRACT: We calculate, for the first time using unquenched lattice QCD, form factors for the rare decay B→Kℓ^{+}ℓ^{-} in and beyond the Standard Model. Our lattice QCD calculation utilizes a nonrelativistic QCD formulation for the b valence quarks and the highly improved staggered quark formulation for the light valence quarks. We employ the MILC 2+1 asqtad ensembles. The form factor results, based on the z expansion, are valid over the full kinematic range of q^{2}. We construct the ratios f_{0}/f_{+} and f_{T}/f_{+}, which are useful in constraining new physics and verifying effective theory form factor symmetry relations. We also discuss the calculation of Standard Model observables.
Physical Review D 09/2013; 88(5). · 4.86 Impact Factor