Description
Cold antihydrogen, the bound state of an antiproton and a positron, is an ideal laboratory to test the fundamental CPT symmetry, one of the cornerstones of the Standard Model of particle physics, by comparing its energy levels to ordinary hydrogen. Hydrogen is one of the best studied atoms experimentally, among the two best-known transitions is the ground-state hyperfine transition ν$_\mathrm{HF}$ with a relative precision of better than $10^{-12}$.
The ASACUSA collaboration has proposed a measurement of ν$_\mathrm{HF}$ in a beam, which allows to perform the experiment in a region far away from the strong magnetic fields needed for antihydrogen creation. Substantial progress has been made to improve the temperature and density of the positron plasma [1,2], which is expected to substantially increase the rate and ground-state fraction of antihydrogen atoms and thus for a measurement of ν$_\mathrm{HF}$. ASACUSA aims at an initial precision of 1 ppm, at which level the finite size of the antiproton becomes visible.
Initially with the aim to establish the in-beam method, ASACUSA has performed a measurement of ν$_\mathrm{HF}$ of ordinary hydrogen using a polarized beam and the same Rabi spectroscopy setup as will be used for antihydrogen and obtained a precision of 2.7 ppb [3]. Within the Standard Model Extension (SME) framework, that describes potential Lorentz invariance and CPT violation scenarios, also measurements using ordinary atoms can be used to constrain symmetry-violating SME coefficients [4]. First experiments have been performed on the orientation dependence of an external static magnetic field for hydrogen hyperfine measurements [5], and preparations are under way to study the hyperfine structure of deuterium.
References
[1] E.D. Hunter et al., EPJ Web of Conferences 262, 01007 (2022)
[2] C. Amsler et al., arXiv:2203.14890 [physics.plasma-ph]
[3] M. Diermaier et al., Nat Commun 8, 15749 (2017).
[4] V.A. Kostelecký & A.J. Vargas, Physical Review D 92, 056002 (2015).
[5] E. Widmann et al., Hyperfine Interact. 240, 5 (2019).
| Presenter name | Eberhard Widmann |
|---|---|
| How will you attend ICAP-27? | I am planning on in-person attendance |
