8th International Symposium on Symmetries in Subatomic Physics (SSP2022)

In-beam measurements of the hydrogen hyperfine splitting to constrain SME coefficients

Not scheduled

20m

Poster presentation Poster Session

Speaker

Lilian Nowak (University of Vienna (AT))

Description

The ASACUSA-CUSP experiment located at CERN’s antiproton decelerator aims at measuring the ground state hyperfine splitting of antihydrogen (H̄) using a beam technique to test CPT symmetry. For this purpose, a beam of cold (~50K) hydrogen has been developed to characterize the antihydrogen spectroscopy apparatus [1]. Beyond serving as a test bench for the H̄ experiment, the hydrogen beamline offers on its own a variety of possible measurements especially in the context of the Standard Model Extension (SME). The SME is an effective field theory that allows CPT and Lorentz symmetries to be broken [2]. A precise measurement of the hydrogen ground state hyperfine splitting was realized in 2017 using the extrapolation of a single hyperfine transition (σ1) reaching a relative precision of 2.7 ppb [3]. Since then several additions to the setup were made allowing the precise measurement of the π1 transition which provides sensitivities to some SME coefficients [4, 5]. A new measurement campaign on hydrogen started in 2021 and focused on π1 precision measurements with swapping external magnetic fields using the σ1 transition as a reference to constrain SME coefficients. The results of these measurements will be presented and an overview on the underlying theory and the experimental setup will be given.
[1] Malbrunot C, et al. 2019 A hydrogen beam to characterize the Asacusa antihydrogen hyperfine spectrometer. Nucl. Instrum. Methods A 935: 110-120.
[2] D. Colladay and A. V. Kostelecký 1998 Lorentz-violating extension of the Standard Model. Phys. Rev. D, 58:116002.
[3] Diermaier M, et al. 2017 In-beam measurement of the hydrogen hyperfine splitting and prospects for antihydrogen spectroscopy. Nat. Commun. 8, 15749.
[4] Malbrunot C, et al. 2018 The ASACUSA antihydrogen and hydrogen program: results and prospects, Phil. Trans. R. Soc. A 376: 2116.
[5] Kostelecký A. V. and Vargas A. J. Lorentz and CPT tests with hydrogen, antihydrogen, and related systems. Phys. Rev., D92(5):056002, 2015.