We present an analysis of the mass of the X(3872) reconstructed
via its decay to J/psi pi++ pi+- using 2.4 fb-1 of integrated luminosity
from p anti-p collisions at s**(1/2) ñ.96 TeV, collected with the CDF II
detector at the Fermilab Tevatron. The possible existence of two nearby
mass states is investigated. Within the limits of our experimental
resolution the data are consistent with a single state, and having
no evidence for two states we set upper limits on the mass difference
between two hypothetical states. Assuming each state contributes equally
to the observed peak, the 95% confidence level upper limit on the mass
difference is 3.6 MeV/c2. Under the single-state model the X(3872)
mass is measured to be 3871.61 +/- 0.16(stat) +/- 0.19(syst) MeV/c2,
which is the most precise determination to date.
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Updated: Monday, 2009 October 26 14:32:24 CDT automatically from input from carol picciolo