Prospects of discovering stable double-heavy tetraquarks at a Tera-$Z$ factory

Understand

Motivated by a number of theoretical considerations, predicting the deeply bound double-heavy tetraquarks $T^{\{bb\}}_{[\bar u \bar d]}$, $T^{\{bb\}}_{[\bar u \bar s]}$ and $T^{\{bb\}}_{[\bar d \bar s]}$, we explore the potential of their discovery at Tera-$Z$ factories.

• Using the process $Z \to b \bar b b \bar b$, we calculate, employing the Monte Carlo generators MadGraph5$\_$aMC@NLO and Pythia6, the phase space configuration in which the~$b b$ pair is likely to fragment as a diquark.
• In a jet-cone, defined by an invariant mass interval $m_{bb} < M_{T^{\{bb\}}_{[\bar q \bar q']}} + \Delta M$, the sought-after tetraquarks $T^{\{bb\}}_{[\bar q \bar q^\prime]}$ as well as the double-bottom baryons,~$\Xi_{bb}^{0,-}$, and $\Omega_{bb}^-$, can be produced.
• Using the heavy quark--diquark symmetry, we estimate $\mathcal{B} (Z \to T^{\{bb\}}_{[\bar u \bar d]} + \; \bar b \bar b) = (1.4^{+1.1}_{-0.5}) \times 10^{-6}$, and about a half of this for the $T^{\{bb\}}_{[\bar{u}\bar{s}]}$ and $T^{\{bb\}}_{[\bar d \bar s]}$.