Observation of two narrow mesons in the D+_s pi^0 and D+_s pi^0 gamma final states. Results from BaBar, Belle and CLEO

The BaBar experiment has discovered a narrow state, denoted as D*_{sJ}(2317)+, near 2.32 GeV/c^2 in the D+s pi^0 invariant mass distribution from inclusive $e^{+}e^{-}$ interactions at center-of-mass energies near 10.6 GeV. The same experiment has hinted the presence of a second new state near 2.46 GeV/c^2 in the D+_s pi^0 gamma mass spectrum. These discoveries have triggered CLEO and Belle experiments in their own search for new states coupled to D+_s meson. They have confirmed the existence of the D*_{sJ}(2317)^+ state and established the evidence for the second state denoted as D*_{sJ}(2458)^+. Belle has reported evidence for both states not only in continuum e+e- annihilations but also in B decays. These two new narrow resonances are characterized by masses significantly lower than predicted by potential models and enough to close off the most natural decay modes, thus forcing isospin-violating transitions. Their discovery has been a surprise because it contradicts the expectations of apparently established theory. This circumstance has led to a great effort on theoretical side as well.