Preliminary results from recent measurements of the antiprotonic helium hyperfine structure

Abstract

We report on preliminary results from a systematic study of the hyperfine (HF) structure of antiprotonic helium. This precise measurement which was commenced in 2006, has now been completed. Our initial analysis shows no apparent density or power dependence and therefore the results can be averaged. The statistical error of the observable M1 transitions is a factor of 60 smaller than that of three body quantum electrodynamic (QED) calculations, while their difference has been resolved to a precision comparable to theory (a factor of 10 better than our first measurement). This difference is sensitive to the antiproton magnetic moment and agreement between theory and experiment would lead to an increased precision of this parameter, thus providing a test of CPT invariance.

Collision Induced Relaxations within the Antiprotonic Helium Hyperfine Structure

“…The results of elastic collisional studies have been presented in previous publications [7,19] and indicate that Γ e is small because the dominating broadening effect is found to be from the Fourier transform of the microwave pulse length. Korenman predicts that Γ e ∼ 2.5Γ i [20] which means that if Γ e is smaller than first predicted then so must Γ i .…”

Antiproton magnetic moment determined from the HFS of antiprotonic helium

“…Bakalov calculated that a broadening of ν ± HF due to an external magnetic field occurs at a rate of Γ ± ∼ 5.6 MHz/G [28]. The similarity between the Fourier transform of the microwave pulse and the spectral line widths [25] confirms that the target region was well shielded during the experiment. Due to referencing to a 10 MHz GPS receiver, the precision of the frequency source is several orders of magnitude less than the resolution of this experiment.…”

“…A more recent calculation [27], based on mea-surements of the collisional broadening [25], predicts ∆ = −0.048 kHz/mbar which is less than the experimental precision. As a negative slope contradicts the predictions, the average of each measurement was taken but the error used was that of the extrapolation to zero density from the fit.…”

“…For illustrative purposes the average of these scans is shown in Fig. 3 where the the dominating broadening effect was due to the Fourier transform of the rectangular microwave pulse of length T [25]. Figure 4b shows that no power dependent trend was observed, therefore all data measured at common target densities could be averaged.…”

Microwave spectroscopy measurements of the hyperfine structure in antiprotonic 3He

“…A waveguide system then transmitted the microwave pulse of 20 μs to the cavity. A self-developed, pulse-amplified laser system [10,11] based on a contiuous wave (CW) laser was used to provide the two laser beams fixed to a wavelength of 723.877 nm. The CW laser consists of a ring Ti : sapphire laser (Coherent MBR-110) pumped by a Nd : YVO 4 laser (Coherent Verdi) and is amplified using Bethune cells pumped by two pulsed Nd:YAG lasers (Coherent Infinity).…”