Towards a next-generation measurement of the fine structure constant*

We present the new Berkeley experiment for measuring the fine-structure constant (alpha) as a test of the Standard model. The current leading determination of alpha reached 0.2 ppb accuracy, and is in 2.5$\sigma $ tension with the value of alpha determined from electron gyromagnetic anomaly experiments [1]. Our new experiment seeks an order of magnitude improvement in sensitivity and systematic uncertainty. By using a beam with a larger beam waist, systematic effects such as Guoy phase or effects from thermal motion of the atoms are minimized [2]. A new interferometer geometry will also be used that can cancel phase shifts from the gravity gradient and from diffraction phases [3,4]. In order to achieve high momentum transfer with a larger beam area, we will discuss progress towards a kW peak power pulsed laser system at 852nm. [1] R. H. Parker, C. Yu, W. Zhong, B. Estey, and H. Mueller, Science 360, 191 (2018). [2] C. Yu, W. Zhong, B. Estey, J. Kwan, R. H. Parker, and H. Mueller, Ann. Phys. 531, 1800346 (2019). [3] Z. Pagel, W. Zhong, R. H. Parker, C. T. Olund, N. Y. Yao, and H. Mueller, arXiv [physics.atom-Ph] (2019). [4] W. Zhong, R. H. Parker, Z. Pagel, C. Yu, and H. Mueller, arXiv [physics.atom-Ph] (2019).