Extended X-ray energy characterization of SIDDHARTA-2 large-area Silicon Drift Detectors up to 50 keV

TL;DR

The paper addresses extending high-precision X-ray spectroscopy of kaonic atoms to heavier systems by characterizing the SIDDHARTA-2 large-area Silicon Drift Detector (SDD) energy response up to 50 keV. It describes the detector system, consisting of 48 SDD arrays totaling ~245 cm$^2$ of active area, and a two-dataset calibration approach using fluorescence lines from Bi, Pd, Ag, Ba, and Tm to map the energy response from 10 to 50 keV. The authors report a linear energy response with relative precision $ΔE/E < 10^{-3}$ and extract energy-resolution parameters with $F ightarrow 0.117$ and $N ightarrow 172$ eV, demonstrating the setup can resolve strong-interaction widths in kaonic atoms. These results support the EXKALIBUR program to measure transitions in kaonic Li, Be, and B (15–50 keV), enabling precise studies of kaon–nucleon interactions and bound-state QED effects in few-body systems. The work validates extending the kaonic-atom program to intermediate-mass/heavier systems with robust calibration and energy-resolution performance.

Abstract

The SIDDHARTA-2 experiment at the DA$Φ$NE collider of INFN-LNF performs high precision light kaonic atoms X-ray spectroscopy to investigate the kaon-nucleon(s) strong interaction in the low-energy (O(10 keV)) regime. A large area Silicon Drift Detectors (SDDs) system has been developed to carry out these measurements. The collaboration aims to extend the measurements campaign to higher mass kaonic atoms, which exhibit transition lines at increased X-ray energies. In this context, the spectroscopic response of the SIDDHARTA-2 SDD system was investigated in terms of linearity and energy resolution up to 50 keV. An accuracy of the energy calibration procedure $ΔE/E < 10^{-3}$ was achieved.

Figures (4)

• Figure 1: Above: Picture of an SDDs array used by the SIDDHARTA-2 experiment. Below: schematic representation of the SDD and of the charge collection process.
• Figure 2: Above: fit of the energy spectrum for the run in beams collision mode, obtained by summing up all the SDDs' calibrated spectra. Below: fit of the calibrated energy spectrum obtained with a $^{169}$Tm target.
• Figure 3: Residuals of the X-ray transitions of interest with the calibration performed with a linear fitting function.
• Figure 4: FWHM of the measured X-ray transition lines as function of the energy obtained with the linear calibration.