HEP-Astro Seminar | Dark Photon Search in Positron Annihilation at Cornell

Dark matter remains a tantalizing puzzle for particle physics and cosmology, with profound implications for understanding the essential nature and evolution of our universe. Its average mass density in the universe is known with considerable and ever-improving precision, yet extensive searches based on conventional explanations such as weakly interacting massive particles continue to yield null results. Newer alternative theories raise the possibility of low mass dark matter, and in so doing open the possibility for discovery in unexplored parameter space, using low-energy, high-intensity experiments. The so-called “dark photon” is a plausible candidate, capable of being produced in electromagnetic interactions such as electron-positron annihilation.

We have proposed the design and construction of a 6 GeV positron beam for fixed target experiments. It will become the highest intensity source of high energy positrons anywhere in the world, providing a unique tool for research in particle- and nuclear-physics. Beam characteristics are optimized for dark matter search experiments that require positrons with high total beam delivery and limited instantaneous beam current. The facility will build on the capabilities of the existing synchrotron injector at Cornell University, augmenting it with beam instrumentation to enable a slow spill of positrons by a resonant extraction mechanism.

I will describe the dynamics of slow extraction of a high energy positron beam from the Cornell synchrotron, and the experiment to search for a dark photon in electron-positron annihilation.