All-charm tetraquark and its contribution to two-photon processes

Prompted by several potential tetraquark states that have been reported by the LHCb, CMS, and ATLAS Collaborations in the di-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>J</a:mi><a:mo>/</a:mo><a:mi mathvariant="normal">Ψ</a:mi></a:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mi>J</d:mi><d:mo>/</d:mo><d:mi mathvariant="normal">Ψ</d:mi><d:mi mathvariant="normal">Ψ</d:mi><d:mo stretchy="false">(</d:mo><d:mn>2</d:mn><d:mi>S</d:mi><d:mo stretchy="false">)</d:mo></d:math> spectra, we investigate their contribution to two-photon processes. Within a nonrelativistic potential model for the all-charm tetraquark states, we calculate the two-photon decay widths of these states and test model-independent sum rule predictions. Imposing such sum-rule constraints allows us to predict the light-by-light scattering cross sections in a consistent way and check if any excess, in comparison to the Standard Model prediction, as reported by ongoing ATLAS experiments, can be attributed to intermediate exotic states.