quarks, which is now given by $$\begin{aligned}
M_{0} & = & e_{Q}+e_{\bar{q}}\end{aligned}$$ This wave function has been also applied for heavy mesons in [@Jaus96] and [@GuHu].

Another possibility is the wave function adopted in [@WSB]: $$\begin{aligned}
\phi(x,{\bf k}_{\perp}) = N\sqrt{\frac{x(1-x)}{\pi \omega^{2}}}
\exp{\left(-\frac{M^{2}}{2\omega^{2}}
\left[x-\frac{1}{2}-\frac{m^{2}_{Q}-m^{2}_{\bar{q}}}{2M^{2}}\right]^{2} \right)}
\exp \left(-\frac{{\bf k}^{2}_{\perp}}{2\omega^{2}}\right) \label{wf3}\end{aligned}$$ where $M$ is the mass of the meson. As shown in [@OXT], the wave functions (\[wf1\]) and (\[wf3\]) satisfy the scaling law [@Neu] $$\begin{aligned}
f_{H} & \propto & \frac{1}{\sqrt{m_{h}}} \;\;\; , \;\;\; m_{h} \rightarrow \infty 
\;\; , \label{slaw}\end{aligned}$$ where $f_{H}$ is the heavy $H$-meson decay constant and $m_{h}$ is the corresponding heavy quark. However, the wave function (\[wf2\]) does not satisfy (\[slaw\]) unless the parameter $\omega$ scales as the square root of the heavy quark mass [@privcom].

We use the wave function (\[wf1\]) in our calculations. The parameters for $\rho  $ and $K^{*}$ are taken from ref. [@Jaus91]. In ref. [@Jaus91] the pion decay constant used has the value $f_{\pi}=92.4\pm  0.2 $ MeV and the $\rho $ decay constant $f_{\rho}/m_{\rho}=152.9 \pm 3.6$ MeV, both taken from experiment. The same value of $\omega$ (called $\beta$ there) is assumed for both the $\pi$ and the $\rho$ mesons. This is in line with the usual 