White dwarf axions, PAMELA data, and flipped-SU(5)

Recently, there are two hints arising from physics beyond the standard model. One is a possible energy loss mechanism due to emission of very weakly interacting light particles from white dwarf stars, with a coupling strength similar to 0.7 x 10(-13), and another is the high energy positrons observed by the PAMELA satellite experiment. We construct a supersymmetric flipped-SU(5) model, SU(5) x U(I)(X) with appropriate additional symmetries, [U(1)(H) ](gauge) x [U(1)(R) x U(1)(Gamma)](global) x Z(2), such that these are explained by a very light electrophilic axion of mass 0.5 meV from the spontaneously broken U(1)(Gamma) and two component cold dark matters from Z(2) parity. We show that in the flipped-SU(5) there exists a basic mechanism for allowing excess positrons through the charged SU(5) singlet leptons, but not allowing antiproton excess due to the absence of the SU(5) singlet quarks. We show the discovery potential of the charged SU(5) singlet E at the LHC experiments by observing the electron and positron spectrum. With these symmetries, we also comment on the mass hierarchy between the top and bottom quarks. (C) 2009 Elsevier B.V. All rights reserved.