Densities of meson and baryon states

In tachyon-free string theories the ratio of the densities of bosonic and fermionic states must approach unity with increasing energy. This observation of Kutasov and Seiberg is considered in the context of a potential stringy description of the hadron spectrum. The densities of the meson and baryon states are approximately equal up to a mass of about 1.7 GeV/${\mathit{c}}^2$, above which the density of baryon states appears greater. In a stringy picture of hadrons, this result implies the existence of a large number of as yet unseen meson states above 1.7 GeV/${\mathit{c}}^2$. These are likely to be exotic, consisting of at least two quarks and two antiquarks, and to be accompanied at still higher masses by exotic baryons as well.