Fermi Ball Detection

The detectability of charged SLAC-bag type structures is considered. These objects, known as Fermi balls, arise from the spontaneous symmetry breaking of a biased discrete symmetry in the early universe. Two classes of experimental searches are discussed. Since Fermi balls in the theoretically favoured mass range are absorbed by the atmosphere, direct experimental searches are confined to space-based facilities. Simple spectrometer and time of flight analysis give a quantitative estimate of Fermi ball mass up to a limit set by the system’s tracking resolution. For the ASTROMAG facility, with a tracking resolution of 50 μm the upper bound on detectable Fermi ball masses is of order 1015 GeV/c2. Charged tracks with sagitta smaller than this resolution would provide evidence in favour of Fermi balls, but only give a lower bound on the discrete symmetry breaking scale φ0. The second class of experimental search proposed relies on the detection of bound Fermi ball states that have been concentrated in terrestrial materials such as oceanic sediment. An analysis of biased discrete symmetry breaking in the early universe has indicated the possibility of production of composite particles called Fermi balls[1]. These Fermi balls are formed out of collapsing fermion-populated domain walls that are generated as the result of spontaneous symmetry breaking of a biased discrete symmetry associated with a real scalar field. A strong Yukawa coupling of generic fermions to this real scalar field insures that fermions are swept up by, and stay within, the domain walls as they collapse upon themselves, thereby forming finite sized false vacuum bags enclosed by a fermion populated domain wall skin. These false vacuum bags collapse and fragment until the soliton nature of the bag structure arrests the collapse. Conceptually, this halting of the collapse is a result of the Fermi gas pressure of the domain wall fermions balancing the false vacuum volume pressure and domain wall surface tension. In the bag model description of the Fermi ball this may occur when the thin domain wall approximation breaks down. The structure that emerges is one of numerous composite particles (Fermi balls) each composed of massless fermions contained in a supermassive SLAC bag like construct with a radius (in GeV) RFB ∼ 2 φ0 (1) and a mass of approximately 100φ0 GeV/c 2 where, φ0 (in GeV) is the symmetry breaking scale. Hence, the Fermi ball mass is dependent on the discrete symmetry breaking scale parameter φ0. The spontaneous symmetry breaking of a biased discrete symmetry is not in itself sufficient to produce cosmologically stable Fermi balls. Such objects can only exist if there exists a net fermion antifermion asymmetry. As the domain wall confinement of fermions prevents fermion number freeze out, a Fermi ball would be completely deflated by fermion pair annihilations if there was a fermion antifermion symmetry. Assuming a fermion antifermion asymmetry, these cosmologically stable Fermi balls can carry a standard model gauge charge which depends on the fermion content of the individual Fermi ball. Conservative constraints on the neutral Fermi ball mass and cross section have already been given in [1]. We focus on the detection of Fermi balls with overall standard model gauge charges, and for simplicity consider the case of an electric charge equal to the sum of the charges of the Fermi ball fermion population. A specific Fermi ball charge prediction can only be the result of a detailed study of fermion-antifermion asymmetries just prior to discrete symmetry breaking,