Speaker
Description
To date all experiments confirmed invariance of the laws of physics with respect to the combined three discrete symmetries Charge conjugation, Parity, and Time reversal (CPT). Nonetheless, beyond Standard Model physics and the matter-antimatter asymmetry of our universe call for continued searches for CPT violation at the highest possible level of precision. Antihydrogen (Hbar), the bound state of an antiproton and a positron, is the ideal testbench toward this goal as it is a stable atom. Therefore, precise spectroscopy methods with long interaction times are applicable, which are copied from (or can be tested with) hydrogen, the matter counterpart of Hbar. Its hyperfine structure of approx. 1.42 GHz is of particular interest for the most stringent comparisons as it is known to mHz absolute precision.
The ASACUSA-Cusp experiment, based at the Antiproton Decelerator of CERN, aims to measure the ground-state hyperfine structure of Hbar via Rabi-type in-beam spectroscopy. In contrast to existing in-trap results on the Hbar hyperfine structure by the ALPHA collaboration, a beam experiment takes Hbar out of the production traps where high magnetic fields cause challenging systematic uncertainties. This benefit is contrasted by the difficulty of forming a sufficiently intense beam of usable properties, as the beam atoms need to be in the ground state, polarised and within an acceptable velocity range.
Recently, ASACUSA achieved record setting plasma properties and Hbar formation rates, which resulted in an increase in beam intensity by two orders of magnitude of up to 320 Hbar per 15 min. production cycle. The impact of plasma parameters on crucial beam properties like quantum state and velocity distributions can now be studied within reasonable times. We will report on the improvements of the Hbar production, the status of the characterization of Hbar beam properties and potentially the first observation of hyperfine transitions in a beam of Hbar.