Electromagnetic form factors of the $B_c$-like tetraquarks: molecular and diquark-antidiquark pictures

TL;DR

This paper calculates magnetic and quadrupole moments of $B_c$-like tetraquarks using molecular and diquark-antidiquark models with QCD sum rules, revealing significant differences and potential insights into their internal structure.

Contribution

It provides the first detailed comparison of magnetic and quadrupole moments of $B_c$-like tetraquarks in two different structural models using QCD light-cone sum rules.

Findings

Magnetic moments differ significantly between models.

Quadrupole moments are small and nonzero.

Results can guide experimental searches.

Abstract

In this study, we use the molecular and diquark-antidiquark tetraquark pictures to investigate magnetic and quadrupole moments of the $B_c$-like ground state tetraquarks with the QCD light-cone sum rules with quantum numbers $J^P = 1^+$. In the numerical analysis, to obtain the magnetic and quadrupole moments of $B_c$-like tetraquark states molecular and diquark-antidiquark forms of interpolating currents, and photon distribution amplitudes have been used. The magnetic moments are acquired as $ \mu_{Z_{{uc \bar u \bar b}}}^{Mol}=1.18^{+0.52}_{-0.40}~\mu_N$, $\mu_{Z_{{uc \bar u \bar b}}}^{Di}=3.05^{+1.19}_{-0.95}~\mu_N$, $\mu_{Z_{dc \bar d \bar b}}^{Mol}=0.32^{+0.18}_{-0.10}~\mu_N$, and $\mu_{Z_{dc \bar d \bar b}}^{Di}=2.38^{+0.95}_{-0.75}~\mu_N$. The hadrons' magnetic and quadrupole moments are another fundamental observable as their mass, which provides information on the underlying quark structure and dynamics. The results obtained in both pictures are quite different from each other. Any experimental measurement of the magnetic moments can provide an understanding of the internal structure of these states. We get nonzero but small values for the quadrupole moments of $B_c$-like tetraquark states showing non-spherical charge distributions. Hopefully, the examinations given in this study will be helpful to an experimental search of them, which will be an interesting research subject.