Radiative E1 decays of X(3872)

Radiative E1 decay widths of X(3872) are calculated through the relativistic Salpeter method, with the assumption that X(3872) is the χc1(2P) state, which is the radial excited state of χc1(1P). We first calculated the E1 decay width of χc1(1P). The result is in agreement with experimental data excellently. Then we calculated the width of X(3872) with the assignment χc1(2P). Results are: Γ(X(3872)→γJ/ψ)=33.0 keV, Γ(X(3872)→γψ(2S))=146 keV and Γ(X(3872)→γψ(3770))=7.09 keV. The ratio Br(X(3872)→γψ(2S))/Br(X(3872)→γJ/ψ)=4.4 agrees with experimental data by BaBar, but is larger than the new up-bound reported by Belle recently. With the same method, we also predicted the decay widths, Γ(χb1(1P))→γϒ(1S)=30.0 keV, Γ(χb1(2P))→γϒ(1S)=5.65 keV and Γ(χb1(2P))→γϒ(2S)=15.8 keV, from which we get the full widths: Γ(χb1(1P))∼85.7 keV and Γ(χb1(2P))∼66.5 keV.