Magnetic moments of open bottom–charm molecular pentaquark octets

Mutuk H., Kang X.

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, vol.879, 2026 (SCI-Expanded, Scopus)

Abstract

We present a comprehensive theoretical investigation of the magnetic moments of open heavy-flavor molecular pentaquarks with quark compositions bc¯qqq and cb¯qqq (where q=u,d,s). Employing a molecular picture in which the pentaquarks are treated as S-wave bound states of a heavy baryon and a meson, we systematically construct the complete spin–flavor wavefunctions for the two distinct SU(3) f octet representations, 81 f and 82 f , arising from symmetric and antisymmetric light-diquark configurations, respectively. Within the framework of the constituent quark model, we calculate the magnetic moments of spin-parity configurations, JP=12−(12+⊗0−) and JP=12−,32−(12+⊗1−), for each member of the bc¯ and cb¯ octets. Our results reveal a striking hierarchy: in the 82 f representation, the 12+⊗0− states exhibit near-universal magnetic moments (μ≈−0.062μN for bc¯qqq and μ≈+0.362μN for cb¯qqq), as a direct consequence of the spin-singlet light-diquark that suppresses light-quark contributions. In contrast, the 81 f representation shows a broad spectrum of values with frequent sign changes, reflecting the active role of the symmetric light-diquark. The clear differences between the bc¯ and cb¯ families demonstrate explicit heavy-quark flavor symmetry breaking in electromagnetic observables. These predictions provide a detailed set of electromagnetic benchmarks that can serve as discriminants for the internal flavor structure and spin configuration of future experimentally observed open heavy-flavor pentaquarks, offering valuable guidance for ongoing and future searches at facilities such as LHCb and Belle II.