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arXiv · 2607.19009

Resolving the $T_{cc}^+$ with $\pi$ Exchange from Lattice QCD

Nelson Pitanga Lachini·Raúl A. Briceño
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Abstract

We revisit the lattice QCD description of the doubly charmed tetraquark $T_{cc}^+$ using a finite-volume scattering formalism that incorporates one-pion exchange nonperturbatively, thereby making the nearest left-hand cut explicit while respecting unitarity and analyticity. We simultaneously determine the $D D^\star \pi$ coupling and the isoscalar $DD^\star$ scattering amplitude by reanalyzing the previously computed finite-volume $DD^\star$ spectrum below the $D^\star D^\star$ threshold, on lattices with pion mass $m_\pi\approx391~{\rm MeV}$. We find that the inclusion of pion exchange changes the $T_{cc}^+$ from a real-valued to a complex-valued pole in the second sheet of the $J^P=1^+$, $DD^\star$ amplitude below threshold. We further predict that the $T_{cc}^+$ pole will move closer to the real-energy axis as the pion mass approaches its physical value.

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Nelson Pitanga Lachini, Raúl A. Briceño. 2026-07-21. Resolving the $T_{cc}^+$ with $\pi$ Exchange from Lattice QCD. https://arxiv.org/abs/2607.19009

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