ALPS II: Commissioning and Data Taking

Astronomical observations have established that the Universe is largely dark, with approximately 85% of the matter made of yet unknown particles. Determining the nature of this dark matter will impact our fundamental knowledge of cosmology, astrophysics and particle physics and is the basis for one of the most extensive searches for new physics beyond the Standard Model that has been so effective in describing our understanding to date. Extensions of the Standard Model predict weakly interacting light (sub-electronvolt) particles, including axions, which have been introduced as a primary candidate for the dark matter. The Any Light Particle Search (ALPS) II experiment is designed to provide the highest search sensitivity for these low-mass particles of any measurements to date that use the Light Shining Through a Wall (LSW) technique. Located at DESY in Hamburg, Germany, the ALPS II detector is now under construction and this award supports the ALPS II group at the University of Florida to perform the upcoming commissioning and science runs using the heterodyne detection scheme developed by the team. The experiment provides a unique and diverse training ground for postdoctoral and student researchers to develop skills in electronics and feedback control systems, vacuum and cryogenics, computational methods and data analysis algorithms, large-scale detector commission and operation, and dark matter physics and cosmology.

The ALPS experiment is designed to search for interactions that turn photons into low-mass particles and vice versa, allowing photons to reemerge behind an otherwise light tight wall. These low-mass particles include axion-like particles, their scalar counterparts, as well as hidden sector photons, and would contribute or even exclusively form the omnipresent dark matter. The ALPS II experiment consists of two 120 m long strings of straightened 5.3 T HERA dipoles on each side of the wall. An optical cavity is used to build up the power to up to 1 MW on one side of the wall while a second cavity amplifies the recreation process on the other side of the wall. In contrast to helioscopes and also haloscopes used also in the search for axion-like particles, ALPS makes no assumptions about stellar evolution; nor does it assume any specific dark matter model. The experiment only depends on proposed fundamental interactions between photons and postulated non-standard-model particles. The ALPS II experiment will surpass past LSW searches by 12 orders of magnitude in regenerated photons and explores a parameter space which has lately been favored by astronomical and other observations.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.