Measurement of the dipion mass spectrum in X(3872) --> J/psi pi+ pi- decays
We measure the dipion mass spectrum in X(3872) --> J/psi pi++ pi+- decays using 360 pb-1 of p anti-p collisions at s**(1/2) = 1.96 TeV collected with the CDF II detector. The spectrum is fit with predictions for odd C-parity (3S_1, 1P_1, and 3D_J) charmonia decaying to J/psi pi++ pi+-, as well as even C-parity states in which the pi+ons are from rho0 decay. The latter case also encompasses exotic interpretations, such as D0 D-bar*0 molecule. Only the 3S_1 and J/psi rho hypotheses are compatible with our data. Since 3S_1 is untenable on other grounds, decay via J/psi rho is favored, which implies C = +1 for the X(3872). Models for different J/psi-rho angular momenta L are considered. Flexibility in the models, especially the introduction of rho-omega interference, enable good descriptions of our data for both L = 0 and 1.
Abulencia, ; A, ; others,
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