Charmed tetraquarks TCC and TCS from dynamical lattice QCD simulations

Charmed tetraquarks T cc = (cc (u) over bar(d) over bar) and Tcs = (cs (u) over bar(d) over bar) are studied through the S-wave meson-meson interactions, D-D, (K) over bar -B, D-D* and (K) over bar -D*, on the basis of the (2 + 1)-flavor lattice QCD simulations with the pion mass m(pi) similar or equal to 410, 570 and 700 MeV. For the charm quark, the relativistic heavy quark action is employed to treat its dynamics on the lattice. Using the HAL QCD method, we extract the S-wave potentials in lattice QCD simulations, from which the meson-meson scattering phase shifts are calculated. The phase shifts in the isospin triplet (I = 1) channels indicate repulsive interactions, while those in the I = 0 channels suggest attraction, growing as m(pi) decreases. This is particularly prominent in the T-cc (J(P) = 1(+), I = 0) channel, though neither bound state nor resonance are found in the range m(pi) = 410-700 MeV. We make a qualitative comparison of our results with the phenomenological diquark picture. (c) 2014 The Authors. Published by Elsevier B.V. All rights reserved.