Abstract
In-beam measurements of the hydrogen hyperfine splitting to constrain Standard Model Extension coefficients
The ASACUSA-CUSP experiment located at CERN’s Antiproton Decelerator aims at measuring the ground state hyperfine splitting of antihydrogen (H????) using a Rabi-like technique to test CPT symmetry. For this purpose, a beam of cold (~50 K) hydrogen has been developed to characterize the antihydrogen spectroscopy apparatus. Beyond serving as a test bench for the H???? experiment, the hydrogen beamline, allows for novel physics measurements especially in the context of the Standard Model Extension (SME), an effective field theory that includes potential violation of CPT and Lorentz symmetries. A new measurement campaign on hydrogen started in 2022 and focused on π₁ and σ transition measurements, using two opposite orientations of the external magnetic field aligning the atoms to constrain SME coefficients. The final results yielded constraints on a set of SME coefficients at a level of 2,3 × 10⁻²¹ GeV. Additionally, the zero-field ground state hyperfine splitting (ν₀) was determined from the π₁ and σ transitions measured at the same static magnetic field, achieving a relative precision of 440 ppt.
Defense committee:
Klaus Jungmann, University of Groningen, NL (reviewer)
Valery V. Nesvizhevsky, European Centre for Neutron Research, FR (reviewer)
Eberhard Widmann (supervisor)
Thomas Pichler (chair)