Measurements of the strong-interaction widths of the kaonic 3He and 4He 2p levels

TL;DR

This study measured the widths of kaonic 3He and 4He 2p states via X-ray transitions, providing new experimental data that align with theoretical predictions and challenge previous larger measurements for 4He.

Contribution

First measurement of the kaonic 3He 2p state width, and refined measurement of the 4He width, using the SIDDHARTA experiment.

Findings

Kaonic 3He 2p width measured for the first time.

Kaonic 4He 2p width significantly smaller than past experimental values.

Results agree with theoretical predictions.

Abstract

The kaonic 3He and 4He X-rays emitted in the 3d-2p transitions were measured in the SIDDHARTA experiment. The widths of the kaonic 3He and 4He 2p states were determined to be Gamma_2p(3He) = 6 \pm 6 (stat.) \pm 7 (syst.) eV, and Gamma_2p(4He) = 14 \pm 8 (stat.) \pm 5 (syst.) eV, respectively. Both results are consistent with the theoretical predictions. The width of kaonic 4He is much smaller than the value of 55 \pm 34 eV determined by the experiments performed in the 70's and 80's, while the width of kaonic 3He was determined for the first time.