What remains a mystery to this day is why strong interactions have not been observed to violate the CP symmetry. One solution, to what has become known as the "Strong CP Problem," introduces an additional symmetry and scalar particles called Axions. This EAGER award will fund research to exploit recent theoretical developments in the search for Axions and Axion Like Particles (ALPs). Specifically, this work will explore designs for an optical delay line that could enhance a Stern-Gerlach type beam splitting effect. The overall goal is to extend the experimentally charted region of Axion space (coupling versus mass) some four orders of magnitude beyond current limits.
This research is aimed at a future experiment that, unlike previous efforts, would be searching for a beam splitting. The laser photon could couple with solar and/or galactic ALPs. Solar ALPs are produced in the sun and, because they interact weakly, can make it through the Earth's atmosphere. In the experimental region, these ALPs would couple to the laser field. The ALP and photon field act as an effective particle/anti-particle pair which will be separated through an interaction with an external magnetic field gradient. This award will look at optical cavity geometries to ascertain the possibility of using an optical delay to enhance the detection of beam splitting. The work is limited to simulations that will be performed, using advanced optical software, to search for suitable cavity geometries. The final cavity design will be selected from several simulated possibilities. The optical software estimates effects of applied coatings, stresses due to mountings and energy loss due to imperfections in the mirror's surface. The software requires the detailed knowledge of surface manufacturing techniques, and so there will be discussions with a company that specializes in manufacturing mirrors for scientific use.
As Broader Impacts, if successful the research performed here could reshape the technology and methodology used for ALP search experiments. Furthermore, the research will be carried out, in part, at Florida A&M University, a Historically Black College and University (HBCU). Thus the research will directly benefit the scientific infrastructure designed to develop underrepresented minorities.
Searches for exotic particles such as axions remain well motivated. Currently, astrophysical data shows that additional mass exist in the universe and, in fact, is paramount to galaxy formation. Previous axion searches, utilizing mirror cavities, have been significantly limited in the sensitivity due to the magnitude of the effects being studied. However, recent theoretical developments may allow scientist to extend the sensitivity of cavity experiments to levels beyond current limitations for all other types of experiment. Central to this research is the coupling between an axion and a photon in an external field gradient. This coupling leads to the formation of both a particle and anti-particle state that separates (beam splitting) in the external field. Such splittings are often referred to as Stern-Gerlach effects, in this case, however, the cavity collapses the states. It is this collapsing that caused a bifurcation of the beam within the cavity. The proposed research aimed to understand how this bifurcating beam would propagate within a stable mirror cavities and if it is possible to enhance the effect through the careful selection of the cavity conditions. Ultimately, our findings suggest that the transverse momentum acquired by photons due to axion-photon coupling can be either enhanced or diminished. These findings have been reported in a pre-print article (http://arxiv.org/abs/1201.6008) and at a conference, "Vistas in Axion Physics."
