Unravelling Pentaquarks with Born--Oppenheimer effective theory

The hidden-charm pentaquark states Pcc̄(4312)⁺, Pcc̄(4380)⁺, Pcc̄(4440)⁺, and Pcc̄(4457)⁺, all with isospin $I = 1/2$, were discovered by the LHCb collaboration in the decay process Λb⁰ → J/ψp K⁻. Although their quantum numbers remain undetermined, these states have generated significant theoretical interest. We analyze their spectrum and decay patterns-including those of their spin partners-within the Born--Oppenheimer effective field theory (BOEFT), a framework grounded in QCD. At leading order in BOEFT, we identify these pentaquark states as bound states in BO potentials that exhibit at short-distance a repulsive octet behavior and a nonperturbative shift due to the adjoint baryons masses, while asymptotically approaching the ΣcD̄ threshold. We further incorporate O(1/mQ) spin-dependent corrections to compute pentaquark multiplet spin splittings. Based on the spectrum, semi-inclusive decay widths to $J/ψ$ and ηc, and the decay width ratios to ΛcD̄ and ΛcD̄^*, we provide the first theoretical predictions for the adjoint baryon masses, which can be confirmed by future lattice QCD studies. Moreover, our analysis supports the quantum number assignments: JP = (1/2)⁻ for Pcc̄(4312)⁺, (3/2)⁻ for Pcc̄(4380)⁺, (1/2)⁻ for Pcc̄(4457)⁺, and (3/2)⁻ for Pcc̄(4440)⁺. We also present results for the lowest bottom pentaquarks.