χ_c2 tensor meson transition form factors in the light front approach

We continue our work on the light-front formulation of quarkonium γ^* γ transition form factors, extending the formalism to J^PC = 2^++ tensor meson states. We present an analysis of γ^* γ→χ_c2 transition amplitude and the pertinent helicity form factors. Our relativistic formalism is based on the light-front quark-antiquark wave function of the quarkonium. We calculate the two-photon decay width as well as three independent γ^* γ transition form factors for J_z = 0,1,2 as a function of photon virtuality Q^2. We compare our results for the two-photon decay width to the recently measured ones by the Belle and BES III collaborations. Even when including relativistic corrections, a very small Γ(λ = 0)/Γ(λ = 2)∼10^-3 ratio is found which is beyond present experimental precision. We also present the form factors as a function of photon virtuality and compare them to the sparse experimental data on the so-called off-shell width. The formalism presented here can be used for other 2^++ mesons, excited charmonia or bottomonia or even light q q̅-mesons.