Understanding the X(3872) with QCD sum rules

Instituto de Física, Universidade de São Paulo, C.P. 66318, 05389-970 São Paulo, SP, Brazil

^a e-mail: matheus@if.usp.br
^b e-mail: navarra@if.usp.br
^c e-mail: mnielsen@if.usp.br
^d e-mail: carina@if.usp.br

Abstract

The nature of the meson X(3872) is still under debate. Here we assume it to be a mixture between charmonium and exotic molecular [cq][qc] states with J^PC = 1⁺⁺ . We find that there is only a small range for the values of the mixing angle, θ, that can provide simultaneously good agreement with the experimental value of the mass and the decay width, and this range is 5⁰ ≤ θ ≤ 13⁰ . In this range we get m_X = (3.77 ± 0.18) GeV and Γ(X → J/ψπ⁺π⁻) = (9.3 ± 6.9) MeV, which are compatible, within the errors, with the experimental values. We, therefore, conclude that the X(3872) is approximately 97% a charmonium state with 3% admixture of ∼88% D⁰ D^∗0 molecule and ∼12% D⁺ D^∗− molecule.