Speaker
Description
Antihydrogen, the antimatter counterpart of hydrogen, provides a unique platform for testing fundamental symmetries in nature. One of its key properties, the ground-state hyperfine splitting (GSHFS), serves as a sensitive probe for Charge-Parity-Time (CPT) symmetry. In hydrogen, this splitting is known to a precision of 1.4 parts in 10¹² [1], offering a precise benchmark for comparison. As the GSHFS is also sensitive to nuclear structure, precise measurements in antihydrogen enable stringent tests of CPT symmetry through direct comparisons with hydrogen.
The ALPHA Collaboration, an international research team at CERN, leads efforts to investigate the fundamental properties of antihydrogen by producing and trapping antihydrogen atoms within a magnetic minimum trap for precision spectroscopy. One of ALPHA’s primary experimental efforts focuses on the GSHFS of antihydrogen, with the aim of performing precise comparisons with the well-known value in hydrogen. Previous measurements have yielded a value of 1,420.4 ± 0.5 MHz [3], limited primarily by statistics and magnetic field uncertainties. The introduction of Be⁺-assisted antihydrogen production, which vastly increases the production rate [4], combined with improved magnet control and characterization [5], has enabled significantly improved measurements of the GSHFS in antihydrogen.
This presentation will report on the most recent antihydrogen GSHFS measurements from the ALPHA experiment, highlighting the experimental method, achieved precision, and the outlook for future improvements in GSHFS spectroscopy at ALPHA.
References
[1] H. Hellwig, R. F. C. Vessot, M. W. Levine, P. W. Zitzewitz, D. W. Allan, and D. J. Glaze, “Measurement of the Unperturbed Hydrogen Hyperfine Transition Frequency,” IEEE Trans. Instrum. Meas., vol. 19, no. 4, pp. 200–209, Nov. 1970, doi: 10.1109/TIM.1970.4313902.
[2] V. A. Kostelecký and A. J. Vargas, “Lorentz and C P T tests with hydrogen, antihydrogen, and related systems,” Phys. Rev. D, vol. 92, no. 5, p. 056002, Sep. 2015, doi: 10.1103/PhysRevD.92.056002.
[3] M. Ahmadi et al., “Observation of the hyperfine spectrum of antihydrogen,” Nature, vol. 548, no. 7665, pp. 66–69, Aug. 2017, doi: 10.1038/nature23446.
[4] R. Akbari et al., “Be+ assisted, simultaneous confinement of more than 15000 antihydrogen atoms,” Nat. Commun., vol. 16, no. 1, p. 10106, Nov. 2025, doi: 10.1038/s41467-025-65085-4.
[5] R. Akbari et al., “The ALPHA-2 apparatus - facilitating experimentation with trapped antihydrogen,” Nucl. Instrum. Methods Phys. Res. Sect. Accel. Spectrometers Detect. Assoc. Equip., vol. 1072, p. 170194, Mar. 2025, doi: 10.1016/j.nima.2024.170194.
| Academic level | PhD student |
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