Abstract
A scalar field dark energy candidate could couple to ordinary matter and photons, enabling its detection in laboratory experiments. Here we study the quantum properties of the chameleon field, one such dark energy candidate, in an ``afterglow'' experiment designed to produce, trap, and detect chameleon particles. In particular, we investigate the possible fragmentation of a beam of chameleon particles into multiple particle states due to the highly non-linear interaction terms in the chameleon Lagrangian. Fragmentation could weaken the constraints of an afterglow experiment by reducing the energy of the regenerated photons, but this energy reduction also provides a unique signature which could be detected by a properly-designed experiment. We show that constraints from the CHASE experiment are essentially unaffected by fragmentation for ϕ4 and 1/ϕ potentials, but are weakened for steeper potentials, and we discuss possible future afterglow experiments.
Highlights
Which decouple from matter through the Damour-Polyakov mechanism [12] and a symmetry-restoring phase transition [13,14,15] in the symmetron case; and Galileons, whose non-canonical kinetic terms effectively decouple them from matter at high densities [16]
We are primarily interested in afterglow experiments, which attempt to produce chameleon particles through photon oscillation in a magnetic field
Low-energy photons regenerated from fragmentation products would have evaded detection by CHASE, whose photomultiplier tube (PMT) detector was insensitive to energies below ∼ 1 eV, but could potentially be detected by upcoming experiments
Summary
Chameleons have been introduced to model the late time acceleration of the expansion of the Universe [10] using a scalar field whose dynamics are governed by a potential V (φ) which depends on a single scale Λ. Where only the relevant terms have been kept For such a model, dark energy is realised when φ ≫ Λ which corresponds to a mass of the scalar field less than Λ, and a range larger (and in practice much larger) than 1 mm where local tests of gravity are very stringent. This model of dark energy leads to the existence of a long range scalar force This force can be screened in the solar system when the chameleon couples to matter. This effective potential is drastically different from V (φ) as it possesses a densitydependent minimum φ(ρ) with a mass m(ρ) which increases with the density of matter This explains why chameleons cannot be seen in the solar system as large a body develops a thin shell which reduces the scalar field gradient in its vicinity.
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