2026/07/21 by Nelson Pitanga Lachini, Raúl A. Briceño
#hep-lat #hep-ph #nucl-th
We revisit the lattice QCD description of the doubly charmed tetraquark Tcc+ using a finite-volume scattering formalism that incorporates one-pion exchange nonperturbatively, thereby making the nearest left-hand cut explicit while respecting unitarity and analyticity. We simultaneously determine the D D^⋆ π coupling and the isoscalar DD^⋆ scattering amplitude by reanalyzing the previously computed finite-volume DD^⋆ spectrum below the D^⋆ D^⋆ threshold, on lattices with pion mass mπ≈391~\rm MeV. We find that the inclusion of pion exchange changes the Tcc+ from a real-valued to a complex-valued pole in the second sheet of the JP=1+, DD^⋆ amplitude below threshold. We further predict that the Tcc+ pole will move closer to the real-energy axis as the pion mass approaches its physical value.