Remarks on the Θ(1540) pentaquark

Additional broader I=0 states in the KN channel near Θ⁺(1540) are expected in many models, making the absence of any signature in the K⁺-deuteron scattering data even more puzzling. In an ideal “three-body” picture the Θ is viewed as two compact ud(1)ud(2) 3¯ color diquarks and an s̅ quark. A “QCD-type” inequality involving m(Θ⁺), m(Λ), the mass of the Λ(1/2^-) L=1 excitation, and that of a new I=0 tetraquark vector meson then follows. The inequality suggests a very light new vector meson, and is violated. We note that “associated production” of the pentaquark with another quadriquark or antipentaquark may be favored. This along with some estimates of the actual production cross sections suggest that the Θ can be found in BaBar or Belle e⁺-e^- colliders.