Implications of an axino LSP for naturalness

Both the naturalness of the electroweak symmetry breaking and the resolution of the strong CP problem may require a small Higgsino mass μ generated by a realization of the DFSZ axion model. Assuming the axino is the lightest supersymmetric particle, we study its implications on μ and the axion scale. Copiously produced light Higgsinos at collider (effectively only neutral next-to-lightest superparticles pairs) eventually decay to axinos leaving prompt multileptons or displaced vertices which are being looked for at the LHC. We use latest LHC7+8 results to derive current limits on μ and the axion scale. Various Higgsino-axino phenomenology is illustrated by comparing with a standard case without lightest axinos as well as with a more general case with additional light gauginos in the spectrum.