Mirror World, Supersymmetric Axion and Gamma Ray Bursts

A modification of the relation between axion mass and the PQ constant permits a relaxation of the astrophysical constraints, considerably enlarging the allowed axion parameter space. We develop this idea in this paper, discussing a model for an {\it ultramassive} axion, which essentially represents a supersymmetric Weinberg-Wilczek axion of the mirror world. The experimental and astrophysical limits allow a PQ scale f_a ~ 10^4-10^6 GeV and a mass m_a ~ 1MeV, which can be accessible for future experiments. On a phenomenological ground, such an {\it ultramassive} axion turns out to be quite interesting. It can be produced during the gravitational collapse or during the merging of two compact objects, and its subsequent decay into e+e- provides an efficient mechanism for the transfer of the gravitational energy of the collapsing system to the electron-positron plasma. This could resolve the energy budget problem in the Gamma Ray Bursts and also help in understanding the SN type II explosion phenomena.