Eur. Phys. J. C (2011) 71: 1762
https://doi.org/10.1140/epjc/s10052-011-1762-7

Regular Article - Theoretical Physics

Delicate interplay between the D ⁰ D ^∗0, ρ ⁰ J/ψ, and ωJ/ψ channels in the X(3872) resonance

¹ Centro de Física das Interacções Fundamentais, Instituto Superior Técnico, Technical University of Lisbon, 1049-001, Lisbon, Portugal
² Centro de Física Computacional, Departamento de Física, Universidade de Coimbra, 3004-516, Coimbra, Portugal

^* e-mail: george@ist.utl.pt

Received: 15 June 2011
Revised: 26 July 2011
Published online: 5 October 2011

Abstract

The nature of the X(3872) enhancement is analyzed in the framework of the Resonance-Spectrum Expansion, by studying it as a regular J ^PC =1⁺⁺ charmonium state, though strongly influenced and shifted by open-charm decay channels. The observed but Okubo–Zweig–Iizuka-forbidden ρ ⁰ J/ψ and ωJ/ψ channels are coupled as well, but effectively smeared out by using complex ρ ⁰ and ω masses, in order to account for their physical widths, followed by a rigorous algebraic procedure to restore unitarity. A very delicate interplay between the D ⁰ D ^∗0, ρ ⁰ J/ψ, and ωJ/ψ channels is observed. The data clearly suggest that the X(3872) is a very narrow axial-vector resonance, with a pole at or slightly below the D ⁰ D ^∗0 threshold.