Hidden-Beauty Charged Tetraquarks and Heavy Quark Spin Conservation

TL;DR

This paper explores the properties of hidden-beauty charged tetraquarks, demonstrating how heavy-quark spin conservation explains observed mass differences and decay patterns, and proposing signatures for an elusive X_b resonance.

Contribution

It introduces a model based on diquark spin interactions to explain mass differences and decay behaviors of beauty sector tetraquarks, supporting their tetraquark nature and suggesting experimental signatures.

Findings

Mass difference scales with quark masses as predicted by QCD.

Decay patterns are compatible with heavy-quark spin conservation.

Supports the tetraquark interpretation of Z states and proposes signatures for X_b.

Abstract

Assuming the dominance of the spin-spin interaction in a diquark, we point out that the mass difference in the beauty sector M(Z_b^prime) - M(Z_b) scales with quark masses as expected in QCD, with respect to the corresponding mass difference M(Z_c^prime) - M(Z_c). Notably, we show that the decays Upsilon(10890) --> Upsilon(nS) pi pi and Upsilon(10890) --> (h_b(1P), h_b(2P)) pi pi are compatible with heavy-quark spin conservation if the contributions of Z_b,Z_b^prime intermediate states are taken into account, Upsilon(10890) being either a Upsilon(5S) or the beauty analog of Y_c(4260). Belle results on these decays support the quark spin wave-function of the Z states as tetraquarks. We also consider the role of light quark spin non-conservaton in Z_b,Z_b^prime decays into B B^* and B^* B^*. Indications of possible signatures of the still missing X_b resonance are proposed.