The 2^-+ assignment for the X(3872)

TL;DR

This paper investigates the implications of assigning the quantum numbers 2^-+ to the X(3872), challenging existing interpretations and analyzing its production, mass, and partner states within various models.

Contribution

It critically examines the 2^-+ assignment for X(3872), assessing its impact on molecular, charmonium, and tetraquark interpretations with new theoretical insights.

Findings

Molecular interpretation becomes less plausible.

Charmonium interpretation faces new difficulties, including production cross section issues.

Tetraquark model predicts a spectrum of partner states.

Abstract

Very recently the BaBar collaboration has put forward a claim that the X(3872) is not a 1^++ resonance, as most of the phenomenological work on the subject was relying on, but rather a 2^-+ one. We examine the consequences of this quantum number assignment for the solution of the X(3872) puzzle. The molecular interpretation appears less likely, and the conventional charmonium interpretation should be reconsidered. There are several well-known difficulties with this interpretation, to which we add a new one: the production cross section at CDF is predicted to be much smaller than that observed. We also confirm, using a relativistic string model, the conclusion from potential models that the mass of the state is not consistent with expectations. In the tetraquark interpretation the 2^-+ assignment implies a rich spectrum of partner states, although the X(3872) may be among the few which are narrow enough to be observable.