Pionic deuterium

TL;DR

This study measures the strong interaction effects in pionic deuterium through high-resolution X-ray spectroscopy, providing new constraints on pion-nucleon interactions and pion absorption parameters.

Contribution

It presents the first high-precision measurements of the shift and broadening in pionic deuterium, linking these to pion-nucleon scattering lengths and absorption couplings.

Findings

Measured the shift as -2356 meV with high precision.

Determined the broadening as 1171 meV, indicating hadronic effects.

Extracted the complex scattering length and pion production threshold parameter.

Abstract

The strong interaction shift $\epsilon$ and broadening {\Gamma} in pionic deuterium have been determined in a high statistics study of the {\pi}D(3p - 1s) X-ray transition using a high-resolution crystal spectrometer. The pionic deuterium shift will provide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are \epsilon = (-2356 {\pm} 31)meV (repulsive) and {\Gamma}1s = (1171+23/-49) meV yielding for the complex {\pi}D scattering length a = [-(24.99 {\pm} 0.33) + i (6.22+0.12/-0.26)]x10-3/m{\pi}. From the imaginary part, the threshold parameter for pion production is obtained to be {\alpha} = (251 +5/-11) {\mu}b. This allows, in addition, and by using results from pion absorption in 3He at threshold, the determination of the effective couplings g0 and g1 for s-wave pion absorption on isoscalar and isovector NN pairs.