On the width of the K-D atom ground state

Experiments at DA Phi NE-Frascati and at J-PARC are scheduled to produce K-D atoms and observe their X-ray cascade down to the 1S ground state (g.s.), thereby measuring its strong-interaction width and shift away from a purely Coulomb state. A width Gamma(1S) less than or similar to 1 keV will ensure good resolution of the X-ray transitions feeding the 1S g.s. Here we study the expected K-D 1S g.s. width from the perspective of global fits to level shifts and widths in heavier kaonic atoms across the periodic table, using K- nuclear optical potentials constructed from (K) over barN chiral interaction models. Special attention is paid to the subthreshold energy at which the (K) over barN subsystem interacts in the K-D atom g.s. Within this approach we predict strong interaction upward level shift of close to 700 eV and width of about 1.2 to 1.3 keV for the K-D atom 1S g.s., in fair agreement with genuinely three-body K-D atom calculations. Comparison is made with pi D- atom phenomenology. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Experiments at DA Phi NE-Frascati and J-PARC aim to produce K-D atoms and observe their X-ray cascade down to the 1S ground state, measuring the strong-interaction width and shift away from a purely Coulomb state. Predictions show a strong interaction upward level shift and width for the K-D atom 1S ground state, aligning with three-body K-D atom calculations and compared with pi D- atom phenomenology.