Signature of a Doubly Charm Tetraquark Pole in DD⁺ Scattering on the Lattice br

The doubly charm tetraquark with flavor ccud and isospin I = 0 is investigated by calculating the DD* scattering amplitude with lattice QCD. The simulation is done on CLS ensembles with dynamical u/d,s quarks and m(pi) similar or equal to 280 MeV for two charm quark masses, one slightly larger and one slightly lower than the physical value. The scattering amplitudes for partial waves l = 0, 1 are extracted near threshold via the Luscher method by considering systems with total momenta PL/(2 pi) =0,1, root 2,2 on two spatial volumes. A virtual bound state pole in the DD* scattering amplitude with l = 0 is found 9.9 (+3.6)(-7.1) MeV below the DD* threshold for the charm quark mass closer to the physical value. This pole is likely related to the doubly charm tetraquark discovered by LHCb less than 1 MeV below the (DD*+)-D-0 threshold. Future lattice simulations closer to the continuum limit and physical quark masses would be valuable to establish this connection systematically.