First measurement of kaonic deuterium X-ray transitions
Abstract
The study of the strong interaction among hadrons at low energies remains one of the key challenges in fundamental physics because of its non-perturbative nature, which makes theoretical descriptions strongly dependent on experimental input. Although substantial progress has been made for systems involving up and down quarks, theoretical models in the strangeness sector continue to face limitations due to the lack of experimental data. Kaonic atoms provide a powerful tool to study the low-energy strong interaction with strangeness through the energy shifts and widths induced on their lowest atomic levels. In this context, kaonic deuterium X-ray spectroscopy has long represented one of the major open challenges in hadronic-atom physics because of its extremely low X-ray yield. This measurement is particularly important because it gives access to the poorly constrained K-n interaction at threshold. Here, we report the first observation of kaonic deuterium X-ray transitions, performed with the SIDDHARTA-2 experiment at the DAΦNE collider. We determine the strong-interaction shift and width of the 1s level to be ε1s=−810.9±24.5 (stat)±2.1 (syst) eV and Γ1s=812±97 (stat)±33 (syst) eV, respectively. This measurement constitutes the most precise experimental determination of the K-d strong interaction at threshold and allows discrimination among competing theoretical models. Combined with the kaonic hydrogen measurement, this result provides the experimental input required to determine the isospin-dependent K-N scattering lengths, with implications for the description of the nature of the molecular interpretation of the Λ(1405), and neutron-rich matter.
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BibTeX
@misc{bazzi2026first,
title = {{First measurement of kaonic deuterium X-ray transitions}},
author = {Massimiliano Bazzi and Francesco Clozza and Carlo Guaraldo and Mihail Antoniu Iliescu and Alessandro Scordo and Francesco Sgaramella and Diana Sirghi and Florin Sirghi and Johann Zmeskal and Leonardo Abbene and Claude Amsler and Francesco Artibani and Giacomo Borghi and Damir Bosnar and Mario Bragadireanu and Antonino Buttacavoli and Marco Carminati and Alberto Clozza and Luca De Paolis and Raffaele Del Grande and Kamil Dulski and Carlo Fiorini and Ivica Friščić and Masa Iwasaki and Aleksander Khreptak and Simone Manti and Johann Marton and Catia Milardi and Pawel Moskal and Fabrizio Napolitano and Hiroaki Ohnishi and Kristian Piscicchia and Fabio Principato and Michał Silarski and Magdalena Skurzok and Antonio Spallone and Kairo Toho and Marlene Tüchler and Oton Vazquez Doce and Eberhard Widmann and Catalina Curceanu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.10749},
eprint = {2608.10749},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.10749},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - First measurement of kaonic deuterium X-ray transitions
AU - Massimiliano Bazzi
AU - Francesco Clozza
AU - Carlo Guaraldo
AU - Mihail Antoniu Iliescu
AU - Alessandro Scordo
AU - Francesco Sgaramella
AU - Diana Sirghi
AU - Florin Sirghi
AU - Johann Zmeskal
AU - Leonardo Abbene
AU - Claude Amsler
AU - Francesco Artibani
AU - Giacomo Borghi
AU - Damir Bosnar
AU - Mario Bragadireanu
AU - Antonino Buttacavoli
AU - Marco Carminati
AU - Alberto Clozza
AU - Luca De Paolis
AU - Raffaele Del Grande
AU - Kamil Dulski
AU - Carlo Fiorini
AU - Ivica Friščić
AU - Masa Iwasaki
AU - Aleksander Khreptak
AU - Simone Manti
AU - Johann Marton
AU - Catia Milardi
AU - Pawel Moskal
AU - Fabrizio Napolitano
AU - Hiroaki Ohnishi
AU - Kristian Piscicchia
AU - Fabio Principato
AU - Michał Silarski
AU - Magdalena Skurzok
AU - Antonio Spallone
AU - Kairo Toho
AU - Marlene Tüchler
AU - Oton Vazquez Doce
AU - Eberhard Widmann
AU - Catalina Curceanu
PY - 2026
DA - 2026/10/17
PB - arXiv
DO - 10.48550/arxiv.2608.10749
UR - https://arxiv.org/abs/2608.10749
AB - The study of the strong interaction among hadrons at low energies remains one of the key challenges in fundamental physics because of its non-perturbative nature, which makes theoretical descriptions strongly dependent on experimental input. Although substantial progress has been made for systems involving up and down quarks, theoretical models in the strangeness sector continue to face limitations due to the lack of experimental data. Kaonic atoms provide a powerful tool to study the low-energy strong interaction with strangeness through the energy shifts and widths induced on their lowest atomic levels. In this context, kaonic deuterium X-ray spectroscopy has long represented one of the major open challenges in hadronic-atom physics because of its extremely low X-ray yield. This measurement is particularly important because it gives access to the poorly constrained K^-n interaction at threshold. Here, we report the first observation of kaonic deuterium X-ray transitions, performed with the SIDDHARTA-2 experiment at the DAΦNE collider. We determine the strong-interaction shift and width of the 1s level to be ε_1s=−810.9±24.5 (stat)±2.1 (syst) eV and Γ_1s=812±97 (stat)±33 (syst) eV, respectively. This measurement constitutes the most precise experimental determination of the K^-d strong interaction at threshold and allows discrimination among competing theoretical models. Combined with the kaonic hydrogen measurement, this result provides the experimental input required to determine the isospin-dependent K^-N scattering lengths, with implications for the description of the nature of the molecular interpretation of the Λ(1405), and neutron-rich matter.
ER -