Revisiting the DD* chiral interactions with the local momentum-space regularization up to the third order and the nature of T cc

We revisit the DD* interactions in chiral effective field theory up to the third order for the first time. We deal with the pion-exchanged interactions via local momentum-space regularization, in which we focus on their long-range behaviors through demanding their contributions vanish at the origin in the coordinate space. The short-range contact interactions and subleading pion-charmed meson couplings are estimated with the phenomenological resonance saturation model. The subleading pion-charmed meson couplings are much weaker than those in the pion-nucleon system, thus the DD* binding mechanism is very different with that of the NN system. We also obtain the analytic structure of the two-pion exchange interactions in the coordinate space, and we find that its asymptotic behavior at long distance is similar to but slightly different than the NN interactions. We get the same asymptotic behavior of the two-pion exchange interaction with that from the HAL QCD method, but appearing in the longer distance rather than 1 < r < 2 fm. The binding solution only exists in the isoscalar channel. Our calculation supports the molecular interpretation of T thorn cc.

Automated summary

In this study, we revisit the DD* interactions in chiral effective field theory up to the third order for the first time. We use local momentum-space regularization to deal with the pion-exchanged interactions and focus on their long-range behaviors. The short-range contact interactions and subleading pion-charmed meson couplings are estimated using a phenomenological resonance saturation model. Our calculations show that the DD* binding mechanism is very different from that of the NN system due to the weaker subleading pion-charmed meson couplings. We also analyze the analytic structure of the two-pion exchange interactions in the coordinate space and find a similar but slightly different asymptotic behavior compared to the NN interactions. The binding solution is only found in the isoscalar channel. Our findings support the molecular interpretation of T thorn cc.