Measurement of the principal quantum number distribution in a beam of antihydrogen atoms

Abstract

The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration plans to measure the ground-state hyperfine splitting of antihydrogen in a beam at the CERN Antiproton Decelerator with initial relative precision of $$10^{-6}$$ 10 - 6 or better, to test the fundamental CPT (combination of charge conjugation, parity transformation and time reversal) symmetry between matter and antimatter. This challenging goal requires a polarised antihydrogen beam with a sufficient number of antihydrogen atoms in the ground state. The first measurement of the quantum state distribution of antihydrogen atoms in a low magnetic field environment of a few mT is described. Furthermore, the data-driven machine learning analysis to identify antihydrogen events is discussed. Graphic Abstract

Hyperfine spectroscopy of antihydrogen, hydrogen, and deuterium

“…Since then efforts are ongoing to increase the H production rate and the ground state population. A first measurement showed, as expected from the three-body recombination mechanism used, a population of states of predominantly high principle quantum numbers [4]. In parallel, ASACUSA is operating a cold hydrogen beam for hyperfine spectroscopy, where the ground-state hyperfine structure of hydrogen was measured with 2.7 ppb precisiony, where the ground-state hyperfine structure of hydrogen was measured with 2.7 ppb precision 1 [5].…”

A Rydberg hydrogen beam for studies of stimulated deexcitation

“…Each field ionizer setting probes a range of nmanifolds (for more details and formulas, please refer to chapter 5 of [4]). A graph of the proton detection rate as a function of the corresponding range of n (horizontal bars) is shown in Fig.…”

“…Unless employing neutral atom traps, experiments cannot rely on slow spontaneous emission to obtain ground state antihydrogen [4]. It is thus of paramount importance to either initially form strongly bound H quantum states (by for example acting, in the case of a threebody-reaction, on the p-e + plasma parameters as discussed in [5]) or enhance the decay of nascent Rydberg H states in current experimental conditions.…”

Upgrade of ASACUSA's Antihydrogen Detector

“…The ASACUSA experiment plans to create an antihydrogen beam to measure the hyperfine splitting of ground-state H using Rabi spectroscopy [2,3]. The hodoscope is used to analyse the num-ber of arriving antihydrogen atoms by detecting their annihilation products [4]. In the previous ASACUSA CUSP beam times the rate of antihydrogen reaching the detector was only a few Hz, but for the upcoming beam times it is expected that the antihydrogen production will be more efficient and a faster readout is needed.…”