English

Can X(3915) be the tensor partner of the X(3872)?

High Energy Physics - Phenomenology 2017-06-07 v2 High Energy Physics - Experiment Nuclear Theory

Abstract

It has been proposed recently (Phys. Rev. Lett. 115 (2015), 022001) that the charmoniumlike state named X(3915) and suggested to be a 0++0^{++} scalar, is just the helicity-0 realisation of the 2++2^{++} tensor state χc2(3930)\chi_{c2}(3930). This scenario would call for a helicity-0 dominance, which were at odds with the properties of a conventional tensor charmonium, but might be compatible with some exotic structure of the χc2(3930)\chi_{c2}(3930). In this paper, we investigate, if such a scenario is compatible with the assumption that the χc2(3930)\chi_{c2}(3930) is a DDˉD^*\bar D^* molecular state - a spin partner of the X(3872)X(3872) treated as a shallow bound state. We demonstrate that for a tensor molecule the helicity-0 component vanishes for vanishing binding energy and accordingly for a shallow bound state a helicity-2 dominance would be natural. However, for the χc2(3930)\chi_{c2}(3930), residing about 100 MeV below the DDˉD^*\bar D^* threshold, there is no a priori reason for a helicity-2 dominance and thus the proposal formulated in the above mentioned reference might indeed point at a molecular structure of the tensor state. Nevertheless, we find that the experimental data currently available favour a dominant contribution of the helicity-2 amplitude also in this scenario, if spin symmetry arguments are employed to relate properties of the molecular state to those of the X(3872). We also discuss what research is necessary to further constrain the analysis.

Keywords

Cite

@article{arxiv.1703.01230,
  title  = {Can X(3915) be the tensor partner of the X(3872)?},
  author = {V. Baru and C. Hanhart and A. V. Nefediev},
  journal= {arXiv preprint arXiv:1703.01230},
  year   = {2017}
}

Comments

LaTeX2e, 23 pages, 2 figures, version to appear in JHEP