Precision measurement of the $3d \to 2p$ x-ray energy in kaonic $^4$He

TL;DR

This study precisely measured the $3d o 2p$ x-ray transition in kaonic $^4$He using advanced detectors, confirming theoretical predictions and resolving a longstanding discrepancy in the strong interaction energy shift.

Contribution

The paper presents the first high-precision measurement of the $3d o 2p$ x-ray energy in kaonic helium-4, improving accuracy and confirming theoretical models.

Findings

Measured the $3d o 2p$ x-ray energy as 6467 ± 3 (stat) ± 2 (syst) eV.

Found the strong-interaction energy-level shift consistent with theoretical calculations.

Resolved a long-standing discrepancy between experimental data and theory.

Abstract

We have measured the Balmer-series x-rays of kaonic $^4$He atoms using novel large-area silicon drift x-ray detectors in order to study the low-energy $\bar{K}$-nucleus strong interaction. The energy of the $3d \to 2p$ transition was determined to be 6467 $\pm$ 3 (stat) $\pm$ 2 (syst) eV. The resulting strong-interaction energy-level shift is in agreement with theoretical calculations, thus eliminating a long-standing discrepancy between theory and experiment.