On the mechanism of T4(6900) tetraquark production

We discuss the production mechanism of a new state, putative fully charm tetraquark, observed recently by LHCb at M = 6.9 GeV in $J/\psi J/\psi$ channel. Both single parton scattering (SPS) and double (DPS) mechanisms are considered. calculate distribution invariant mass four-quark system $M_{4c}$ for SPS DPS $c c \bar c$ $k_t$-factorization approach with modern unintegrated gluon functions (UGDFs). The so-calculated contribution is almost two orders magnitude larger than one, but tetraquark formation unknown present. Imposing window around resonance position we corresponding $p_{t,4c}$ -- potential transverse momentum. cross section continuum calculated addition, again including (box diagrams) contributions which similar size. probability estimated trying to reproduce signal-to-background ratio. calculation $g g \to T_{4c}(6900)$ fusion performed $k_T$-factorization assuming different spin scenarios ($0^+$ $0^-$). $0^+$ assignment preferred over $0^-$ one comparison momentum signal background preliminary data dominance. There no reliable tetraquarks present as this complicated multi-body problem.