Abstract
Antihydrogen, the lightest atom consisting purely of antimatter, is an ideal laboratory to study the CPT symmetry by comparison with hydrogen. With respect to absolute precision, transitions within the ground-state hyperfine structure (GS-HFS) are most appealing by virtue of their small energy separation. ASACUSA proposed employing a beam of cold antihydrogen atoms in a Rabi-type experiment, to determine the GS-HFS in a field-free region. Here we present a measurement of the zero-field hydrogen GS-HFS using the spectroscopy apparatus of ASACUSA’s antihydrogen experiment. The measured value of νHF=1,420,405,748.4(3.4) (1.6) Hz with a relative precision of 2.7 × 10−9 constitutes the most precise determination of this quantity in a beam and verifies the developed spectroscopy methods for the antihydrogen HFS experiment to the p.p.b. level. Together with the recently presented observation of antihydrogen atoms 2.7 m downstream of the production region, the prerequisites for a measurement with antihydrogen are now available within the ASACUSA collaboration.
Highlights
Antihydrogen, the lightest atom consisting purely of antimatter, is an ideal laboratory to study the CPT symmetry by comparison with hydrogen
Most notable from a precision point of view are the recent measurement of the 1S–2S transition via two-photon spectroscopy[3] and the determination of the hyperfine splitting in hydrogen maser experiments in the early 1970s
Antihydrogen spectroscopy promises precise tests of the CPT symmetry, which is a cornerstone of the Standard Model of particle physics
Summary
Antihydrogen, the lightest atom consisting purely of antimatter, is an ideal laboratory to study the CPT symmetry by comparison with hydrogen. With respect to absolute precision, transitions within the ground-state hyperfine structure (GS-HFS) are most appealing by virtue of their small energy separation. ASACUSA proposed employing a beam of cold antihydrogen atoms in a Rabi-type experiment, to determine the GS-HFS in a field-free region. Most notable from a precision point of view are the recent measurement of the 1S–2S transition via two-photon spectroscopy[3] and the determination of the hyperfine splitting in hydrogen maser experiments in the early 1970s (refs 4–9). Among the spectroscopic tests of CPT, the comparison of the ground-state hyperfine structure (GS-HFS) of hydrogen and antihydrogen has the potential to reach the highest sensitivity on an absolute energy scale[25,26,27].
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