Doubly Charmed Tetraquark ${T}_{cc}^{+}$ from Lattice QCD near Physical Point

Abstract

The doubly charmed tetraquark ${T}_{cc}^{+}$ 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 $m_π$ = 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 $E_{pole}$ = −59($^{+53}_{-99}$)($^{+2}_{-67}$) 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 $m_π$ decreases to its physical value by using a potential modified to $m_π$ = 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.