Traces of the Θ⁺ pentaquark in K⁺-nucleus dynamics

Long-standing anomalies in K⁺-nucleus integral cross sections could be resolved by extending the impulse-approximation tρ optical-potential framework to incorporate K⁺ absorption on pairs of nucleons. Substantially improved fits to the data at p_lab ∼ 500-700 MeV/c are obtained. An upper bound on the absorption cross section per nucleon is derived, σ_abs^(K+)/A ∼ 3.5 mb. We conjecture that the underlying microscopic absorption process is K⁺ nN →⁺ N, where Θ⁺ (1540) is the newly discovered exotic Y = 2, 1 = 0, Z = 1 pentaquark baryon, and estimate that σ(K⁺ d →Θ⁺ p) is a fraction of millibarn. Comments are made on Θ⁺ production reactions on nuclei.