Narrow Results

We discuss how to use Morgan's pole counting rule to distinguish a molecular state from an 'elementary' particle. As two examples we focus on X(3872) and f₀(980) particles. A molecule may be generated from a meson loop bubble chain, and an 'elementary' particle is related to an explicit interaction field in the effective lagrangian and propagates with a Breit–Wigner propagator. For X(3872) it is found that the data favor the 'elementary' particle explanation. For f₀(980) the study becomes much more difficult, since highly nonperturbative dynamics is involved. A unitarization model analysis suggests that f₀(980)'s property is quite exotic. Unlike other light scalars, it does not behave like a state, and could be interpreted as a molecule.

We discuss how to use Morgan's pole counting rule to distinguish a molecular state from an ‘elementary’ particle. As two examples we focus on X(3872) and f₀(980) particles. A molecule may be generated from a meson loop bubble chain, and an ‘elementary’ particle is related to an explicit interaction field in the effective lagrangian and propagates with a Breit–Wigner propagator. For X(3872) it is found that the data favor the ‘elementary’ particle explanation. For f₀(3872) the study becomes much more difficult, since highly non-perturbative dynamics is involved. A unitarization model analysis suggests that f₀(980)'s property is quite exotic. Unlike other light scalars, it does not behave like a state, and could be interpreted as a molecule.