Observation of the narrow state x (3872) --> j/psi pi+ pi- in pbar p collisions at s**(1/2) = 1.96 tev

The authors report the observation of a narrow state decaying into J/{psi}{pi}{sup +}{pi}{sup -} and produced in 220 pb{sup -1} of {bar p}p collisions at {radical}s = 1.96 TeV in the CDF II experiment. They observe 730 {+-} 90 decays. The mass is measured to be 3871.3 {+-} 0.7(stat) {+-} 0.4(syst) MeV/c{sup 2}, with an observed width consistent with the detector resolution. This is in agreement with the recent observation by the Belle Collaboration of the X(3872) meson