Signature decay modes of the compact doubly-heavy tetraquarks $T_{bb\bar{u} \bar{d}}$ and $T_{bc\bar{u} \bar{d}}$

TL;DR

This paper predicts weak decay modes of stable doubly-heavy tetraquarks, focusing on transitions involving other tetraquarks, and discusses how experimental observation can reveal their internal structure.

Contribution

It provides theoretical predictions for semileptonic and non-leptonic weak decays of doubly-heavy tetraquarks using heavy quark symmetry, including potential experimental signatures.

Findings

Identification of the $T_{cc}^+$ tetraquark with specific mass and decay width.

Predicted decay channels involving transitions between tetraquarks.

Potential for experimental measurements to reveal tetraquark internal structure.

Abstract

Based on the expectations that the lowest-lying doubly-bottom tetraquark $T_{bb\bar u \bar d}$ ($J^P = 1^+$) and the bottom-charm tetraquark $T_{bc\bar u \bar d}$ ($J^P = 0^+$) are stable against strong and electromagnetic decays, we work out a number of semileptonic and non-leptonic weak decays of these hadrons, making use of the heavy quark symmetry. In doing this, we concentrate on the exclusive decays involving also tetraquarks in the final states, i.e., transitions such as $T_{bb\bar u \bar d} \to T_{bc\bar u \bar d}\, (\ell^- \nu_\ell,\, h^-)$ and $T_{bc\bar u \bar d} \to T_{cc\bar u \bar d}\, (\ell^- \nu_\ell,\, h^-)$, where $h^- = \pi^-, \rho^-, a_1^-, D^-_s, D^{*-}_s$. So far, only the $J^P = 1^+$ tetraquark $T_{cc\bar u \bar d}$ has been discovered, which we identify with the $I = 0$ $T_{cc}^+$ object, compatible with $J^P = 1^+$ and having the pole mass relative to the $D^{*+} D^0$ mass threshold and decay widths $\delta m = M (T_{cc}^+) - ( M (D^{*+}) + M (D^0) ) = - 360 \pm 40^{+4}_{-0}$ keV and $\Gamma (T_{cc}^+) = 48^{+2}_{-14}$ keV. Experimental discoveries of the transitions worked out here, and related ones involving doubly-heavy baryons, will quantify the diquark-antidiquark component of these tetraquarks.