Doubly Charmed Tetraquark Tcc+ from Lattice QCD near Physical Point

Abstract

The doubly charmed tetraquark Tcc+ recently discovered by the LHCb Collaboration is studied on the basis of (2+1)-flavor lattice QCD simulations of the D∗D system with nearly physical pion mass mπ=146 MeV. The interaction of D∗D in the isoscalar and S-wave channel, derived from the hadronic spacetime correlation by the HAL QCD method, is attractive for all distances and leads to a near-threshold virtual state with a pole position Epole=-59(-99+53)(-67+2) keV and a large scattering length 1/a0=0.05(5)(-2+2) fm-1. The virtual state is shown to evolve into a loosely bound state as mπ decreases to its physical value by using a potential modified to mπ=135 MeV based on the pion-exchange interaction. Such a potential is found to give a semiquantitative description of the LHCb data on the D0D0π+ mass spectrum. Future study is necessary to perform physical-point simulations with the isospin-breaking and open three-body-channel effects taken into account.