Probing the structure of $\chi_{c1}(3872)$ with photon transition form factors

Abstract

We propose to study the structure of the enigmatic $\chi_{c1}(3872)$ axial vector meson through its $\gamma^*_L \gamma \to \chi_{c1}(3872)$ transition form factor. We derive a light-front wave function representation of the form factor for the lowest $c \bar c$ Fock-state. We found that the reduced width of the state is well within the current experimental bound recently published by the Belle collaboration. This strongly suggests a crucial role of the $c \bar c$ Fock-state in the photon-induced production. Our results for the $Q^2$ dependence can be tested by future single tagged $e^+ e^-$ experiments, giving further insights into the short-distance structure of this meson.