PoS - Proceedings of Science
Volume 310 - XVII International Conference on Hadron Spectroscopy and Structure (Hadron2017) - Plenary
Pole structure and compositeness
J.A. Oller
Full text: pdf
Pre-published on: February 16, 2018
Published on: March 20, 2018
Abstract
We present in this talk a series of new results on the nature of a bound state or resonance based on the calculation of the expectation values of the number operators of the free particles in the state of interest. In this way, a new universal criterion for the elementariness of a bound state emerges. In the case of large particle wavelengths compared to the range of their interaction, a new closed formula for the compositeness of a bound state in a two-particle continuum is obtained. The extension of these results to resonances with respect to the open channels can be given by making use in addition of suitable phase-factor transformations as also reviewed here. We end with a discussion on the $X(3872)$ as possible double- or triple-pole virtual state, which would be the first case in particle phenomenology.
DOI: https://doi.org/10.22323/1.310.0012
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