Ultraperipheral photoproduction of vector mesons in the nuclear Coulomb field and the size of neutral vector mesons

We point out a significance of ultraperipheral photoproduction of vector mesons in the Coulomb field of nuclei as a means of measuring the radius of the neutral vector meson. This new contribution to the production amplitude is very small compared to the conventional diffractive amplitude, but because of large impact parameters inherent to the ultraperipheral Coulomb mechanism its impact on the diffraction slope is substantial. We predict appreciable and strongly energy dependent increase of the diffraction slope towards very small momentum transfer.The magnitude of the effect is proportional to the mean radius squared of the vector meson and is within the reach of high precision photoproduction experiments, which gives a unique experimental handle on the size of vector mesons

A critique of astrophysical applications of Hagedorn's bootstrap

It has been shown that Hagedorn's bootstrap should not be applied to hadronic matter at densities large against nuclear densities. The correct predictions of the thermodynamical model do not use any relation between the mass of the fireballs and their size, whereas the astrophysical applications depend on the unreasonable assumption that the size is independent of the mass. The most spectacular prediction of the bootstrap, namely violent black hole explosions yielding 10/sup 15/ g in the last millisecond, is shown to be completely unfounded, even if such an assumption is made. (21 refs)