IFIC seminars: Doubly heavy tetraquarks: insights from experiment and lattice QCD

by Prof. Vadim Baru (Ruhr-Universität Bochum)

Tuesday 17 Dec 2024, 12:00 → 14:00 Europe/Madrid

Seminario SS6. Sótano ()

A precondition for understanding exotic near-threshold states is the accurate extraction of their properties from experimental data. 

Key information lies in the pole position and residue of a state, which characterizes its coupling strength to nearby hadronic thresholds. 

To address these quantities, systematic theoretical approaches are required to analyze experimental data in a way that respects the principles of analyticity and unitarity.
Effective Field Theory (EFT) offers a model-independent approach within the relevant energy range near the threshold, which enables accurate predictions for observables and insights into potential molecular candidates and their heavy-quark partners.

In this talk, we will mainly focus on the formulation and application of chiral EFT to DD* scattering, crucial for extracting the properties of the Tcc state from experiment and lattice data.  We demonstrate that explicit account for the longest-range one-pion exchange interaction, including the energy scales associated with the three-body and left-hand cuts, is important for preserving the correct analytic structure of the $DD^*$ scattering amplitude near the threshold. 

The proposed approach serves as an alternative to the well-known Lüscher method, which is not applicable in the presence of left-hand cuts, for predicting infinite-volume observables based on lattice spectra.  

Using $\chi$EFT up to next-to-leading order, we extract the low-energy isoscalar $DD^*$ scattering amplitude from data at both physical and unphysical pion masses and predict the light-quark mass dependence of the $T_{cc} $ pole position. We also analyse lattice data in the isovector $DD^*$ channel and highlight the differences compared to the isoscalar case.