Speaker
Description
The ASACUSA experiment aims at a precise measurement of the ground state hyperfine (GSHFS) splitting of antihydrogen with an initial relative precision of $\leq 10^{-6}$ to test the combined CPT symmetry. The Rabi-type measurement will be carried out in a polarized beam of antihydrogen atoms that is synthesized via three-body-recombination (3BR) of positrons and antiprotons at CERN's Antiproton Decelerator complex [1]. A measurement with ground-state hydrogen atoms using the spectroscopy apparatus envisioned for antihydrogen yielded a 3ppb-precise value of the GSHFS [2], improving the previous measurement in a beam by more than an order of magnitude.
Antimatter atoms are produced via 3BR in a wide range of highly excited Rydberg states [3,4]. Thus, compared to hydrogen, the main challenge with antihydrogen lies in the production of GS atoms. Measurements [5,6] indicate that the rate of low-lying states needs to be increased by more than an order of magnitude to make measurements possible. In this view, the ASACUSA-CUSP collaboration is investigating different techniques to increase the GS fraction in the beam relying on stimulated deexcitation. I will present here novel developments on light-stimulated deexcitation [7] employed directly at the antihydrogen formation region that allow driving the formed atoms toward ground-state and thus enable a more efficient beam formation and polarization. As a consequence the ground state fraction at the cavity would be significantly increased. I will conclude on the future ASACUSA-CUSP physics program and it's prospects for antimatter spectroscopy measurements.
[1] Kuroda N., Ulmer S., Murtagh D. et al., A source of antihydrogen for in-flight hyperfine spectroscopy, Nat Commun 5, 3089 (2014)
[2] Diermaier M., Jepsen C., Kolbinger B. et al., In-beam measurement of the hydrogen hyperfine splitting and prospects for antihydrogen spectroscopy, Nat Commun 8, 15749 (2017)
[3] Robicheaux F., Atomic processes in antihydrogen experiments: A theoretical and computational perspective, J. Phys. B: At. 41, 192001 (2008)
[4] Radics B., Murtagh D. J., Yamazaki Y. and Robicheaux F., Scaling behavior of the ground-state antihydrogen yield as a function of positron density and temperature from classical-trajectory Monte Carlo simulations, Phys. Rev. A 90, 032704 (2014)
[5] Malbrunot C., Amsler C. et al., The ASACUSA antihydrogen and hydrogen program: results and prospects, Phil. Trans. R. Soc. A. 37620170273 (2018)
[6] Kolbinger B. et al., Measurement of the Principal Quantum Number Distribution in a Beam of Antihydrogen Atoms, Eur. Phys. J. D (2021) 75: 91
[7] Wolz T., Malbrunot C., Vieille-Grosjean M. and Comparat D., Stimulated decay and formation of antihydrogen atoms, Phys. Rev. A 101, 043412 (2020)
