Gamma rays from the Galactic bulge and large extra dimensions (original) (raw)

An intriguing feature of extra dimensions is the possible production of Kaluza--Klein gravitons by nucleon-nucleon bremsstrahlung in the course of core collapse of massive stars, as pointed out by Hannestad and Raffelt. In this event Kaluza--Klein gravitons are copiously produced and a significant fraction of them remains trapped around the newly born neutron stars. They slowly decay into 2 gamma rays, making neutron stars gamma-ray sources. In this letter, we strengthen considerably the limits on the radius of compactification of extra-dimensions for small number n of them, or alternatively the fundamental scale of quantum gravity, considering the gamma-ray emission of the whole population of neutron stars sitting in the Galactic bulge, instead of the closest member of this category. For n=1 the constraint on the compactification radius is R<400μm, overlapping with the distance (180μm) at which Newtons law is directly measured. In addition, for n=1 and n=2, the fundamental energ...