Abstract
Phys.Rev.Lett.100:182002,2008 The $B_c^{\pm}$ meson is observed through the decay $B_c^{\pm} \to J/\psi
\pi^{\pm}$, in data corresponding to an integrated luminosity of 2.4 fb$^{-1}$
recorded by the CDF II detector at the Fermilab Tevatron. A signal of
$108\pm15$ candidates is observed, with a significance that exceeds $8 \sigma$.
The mass of the $B_c^{\pm}$ meson is measured to be 6275.6 $\pm$ 2.9 (stat.)
$\pm$ 2.5 (syst.) MeV/$c^2$.