Speaker
Description
The study of doubly heavy tetraquarks has gained substantial topical interest, primarily boosted by the recent discovery of doubly charmed tetraquark $T_{cc}$ and by its phenomenological prospects. While $T_{cc}^+$ is observed to be $\sim$0.4 MeV below the $DD^*$ threshold, multiple lattice calculations point to a deep binding ($\mathcal{O}(100 MeV)$) in $T_{bb}$. However, the predictions for the binding in $T_{bc}$ are scattered. We report a lattice study of $DB^*$-$BD^*$ scattering in the isoscalar axial-vector channel with the explicitly exotic flavor $bc\bar u\bar d$. The simulation is performed on four $N_f=2+1+1$ MILC gauge ensembles with different lattice spacings and volumes. The $DB^*$ scattering amplitudes are extracted from the low-lying finite-volume spectra following the amplitude analysis {\it \'a la} L\"uscher. The light quark mass ($m_{u/d}$) dependence of the continuum extrapolated amplitudes is analyzed to determine the fate of the $bc\bar u\bar d$ at the physical $m_{u/d}$. We find strong evidence for a bound $bc\bar u\bar d$ tetraquark at physical $m_{u/d}$ in this channel. We also determine the critical $m_{u/d}$ at which such a state becomes unbound.
| Topical area | Hadronic and Nuclear Spectrum and Interactions |
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