With reference to a very precise but little-known mass quantization scheme, the masses of the X(3872) and X(3940) mesons are compared with the various c-cbar meson families.
The only statistically significant and consistent match is with the chi_c(1). This result is in agreement with the experimental constraints on
the possible J^PC quantum numbers of the X(3872), recently published by the Belle Collaboration,
where the accumulated evidence strongly favors a J^PC = 1++ assignment for the X(3872).
12.40.Yx Hadron mass models and calculations
14.40.Gx Mesons with S=C=B=0, mass>2.5 GeV (including quarkonia)