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: 2.04). 43(1). DOI: 10.1140/epja/i2009-10893-3
Source: OAI

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:

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

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

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

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

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

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

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