Abstract
We present a new evaluation of the negatively charged pion mass based on the simultaneous spec-troscopy of pionic nitrogen and muonic oxygen transitions using a gaseous target composed by a N 2 /O 2 mixture at 1.4 bar. We present the experimental setup and the methods for deriving the pion mass value from the spatial separation from the 5g -- 4 f $\pi$N transition line and the 5g -- 4 f $\mu$O transition line used as reference. Moreover, we discuss the importance to use dilute targets in order to minimize the influence of additional spectral lines from the presence of remaining electrons during the radiative emission. The occurrence of possible satellite lines is investigated via hypothesis testing methods using the Bayes factor.
Highlights
With increasing experimental accuracy, in the ’80s discrepancies between pionic atoms and pion decay results showed up
We present a new evaluation of the negatively charged pion mass based on the simultaneous spectroscopy of pionic nitrogen and muonic oxygen transitions using a gaseous target composed by a N2/O2 mixture at 1.4 bar
We present the experimental set-up and the methods for deriving the pion mass value from the spatial separation from the 5g − 4 f πN transition line and the 5g − 4 f μO transition line used as reference
Summary
In the ’80s discrepancies between pionic atoms and pion decay results showed up. Solution A is in complete disagreement with evaluations obtained from the pion decay measurement at rest [17,18,19] To solve this dilemma, in the ’90s our collaboration designed and realized a new experiment with a gaseous nitrogen target for having X-rays emitted from a purely hydrogen-like pion-nucleus system. In the ’90s our collaboration designed and realized a new experiment with a gaseous nitrogen target for having X-rays emitted from a purely hydrogen-like pion-nucleus system In this experiment, the energy of the 4 keV X rays of the 5g → 4 f line was measured with a reflection spectrometer set up in Johann geometry. We present a brief general description of the experiment (Sec. 3) and the detailed formulas used for extracting the pion mass from the line positions (Sec. 4)
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