Search for Chameleon Particles Using a Photon-Regeneration Technique

We report the first results from the GammeV search for chameleon particles, which may be created via photon-photon interactions within a strong magnetic field. Chameleons are hypothesized scalar fields that could explain the dark energy problem. We implement a novel technique to create and trap the reflective particles within a jar and to detect them later via their afterglow as they slowly convert back into photons. These measurements provide the first experimental constraints on the couplings of chameleons to photons.

Figure 1

The GammeV apparatus.

Figure 2

Expected afterglow rate for various values of ${\beta }_{\gamma }$. The solid curves are for chameleons with masses of ${10}^{-4}\mathrm{eV}$ while the dotted curves are for $5\times {10}^{-4}\mathrm{eV}$ chameleons. Our observation time window for pseudoscalar chameleons is shown shaded in yellow; the corresponding time window for scalar chameleons is shifted to the right by about 700 sec.

Figure 3

Region excluded by GammeV to $3\sigma$ for pseudoscalar particles (solid blue region) and for scalar particles (region between green lines).