The problem of intrinsic charm of a hadron has been discussed for already 40 years. However, only in 2022, the NNPDF collaboration obtained using the LHCb data the first convincing indications of the existence of intrinsic charm in a proton. The differential cross section of J/psi pair production was measured by the COMPASS experiment which used a 190 GeV/c pion beam scattering off different nuclear targets.

The results obtained allow studying charmonia production mechanisms and putting the upper limit on the J/psi pair production cross section assuming its production through the intrinsic charm mechanism. The distribution of the invariant mass of J/psi pairs obtained by COMPASS does not exhibit any statistically significant signals from exotic tetraquark states observed by LHCb.
(Based on materials of the candidate dissertation.)