The exclusive production of a fully heavy tetraquark and a photon in electron-positron collision

TL;DR

Addresses the exclusive production of fully heavy tetraquarks in $e^{+}e^{-}$ annihilation with a hard photon, using NRQCD factorization to separate short-distance production from long-distance matrix elements for both molecule-like and compact states with spins $J=0,1,2$. The study develops a two-step transition framework and employs potential-model inputs for the wave functions at the origin to estimate LDME values, computing cross sections at Belle II and future $Z$ factories. Numerical results show cross sections typically in the ab to sub-ab range, implying negligible event rates and making observation unlikely at current or planned facilities. The work highlights the sensitivity to nonperturbative inputs and calls for more precise determinations of wave functions at the origin to enable reliable predictions for fully heavy tetraquark production.

Abstract

The exclusive production of fully heavy tetraquark ($T(bb\bar{b}\bar{b})$, $T(cc\bar{c}\bar{c})$ and $T(bc\bar{b}\bar{c})$) in association with a hard photon in electron-positron collisions is calculated within the framework of non-relativistic QCD. Both inner structures of molecule-like state and compact state with $J=0,1,2$ for the fully heavy tetraquark are discussed. We find that it is dismal to observe any fully heavy tetraquarks in either the compact configuration or the molecule-like configuration through such exclusive processes at either Belle II or future Z factories like CEPC and FCC-ee.

Figures (2)

• Figure 1: Typical Feynman diagrams for $e^{+}+e^{-}\to \gamma^{*}/Z^{0}\to T+\gamma$. Diagram (a) represents the $s$-channel diagrams and (b) designates the $t$-channel diagrams.
• Figure 2: The differential distributions $\mathrm{d}\sigma/\mathrm{d} cos\theta$ and $\mathrm{d}\sigma/\mathrm{d} p_t$ for the process $e^{+}+e^{-} \to T_C((cc)[^3S_1]^{\bar{\mathbf{3}}}-(\bar{c}\bar{c})[^3S_1]^{\mathbf{3}})(J)+\gamma$ with $J=0, 2$ at the B factory, where $\theta$ is the angle between the tetraquark and the beam and $p_t$ is the transverse momentum of the tetraquark.