The Glueball Candidate η(1440) as ηRadial Excitation

Abstract

The Particle Data Group decided to split the $η(1440)$ into two states, called $η_L$ and $η_H$. The $η(1295)$ and the $η_H$ are supposed to be the radial excitations of the $η$ and $η'$, respectively. The $η_L$ state cannot be accomodated in a quark model; it cannot be a $q\bar q$ state, however, it might be a glueball. In this contribution it is shown that that the $η(1295)$ does not have the properties which must be expected for a radially excited state. The splitting of the $η(1440)$ is traced to a node in the wave function of a radial excitation. Hence the two peaks, $η_L$ and $η_H$, originate from one resonance which is interpreted here as first radial excitation of the $η$.