INTERMADIATE MASS KAONIC ATOMS MEASUREMENT – THE SIDDHARTA-2 EXPERIMENT

SIDDHARTA-2 — intermediate kaonic atoms measurements

Kaonic atoms represent an ideal tool to study Quantum Chromodynamics (QCD) in the strangeness sector at low-energy regime, where it cannot be described with a perturbative approach. Their measurement allow a direct access to the K⁻N interaction at threshold, without the need of an extrapolation as in the case of scattering experiments: the relative energy between the kaon and the nucleus is already at the level of few keV.
Between 2021 and 2023, the SIDDHARTINO and SIDDHARTA-2 apparata collected 76 pb⁻¹ of integrated luminosity measuring kaonic helium-4 (K⁴He) in gas target. The first run took place with SIDDHARTINO during the beam optimization phase of DAΦNE in Spring 2021 and was dedicated to optimize the collider and setup performances (link). In June 2022, a new kaonic helium measurement was performed with the complete SIDDHARTA-2 setup installed on the Interaction Point of the DAΦNE collider (link), to assess and adjust the experimental apparatus in view of the kaonic deuterium measurement, currently in progress. The spectrum obtained, after a background suppression operated with the Kaon Trigger and the VETO systems data, is shown below, together with a table summarizing the results. More details can be found in [1].

The total 76 pb⁻¹ spectrum acquired from the SDDs by the SIDDHARTINO and SIDDHARTA-2 experiments measuring K⁴He [1]. The spectrum was obtained after a background suppression based on the Kaon Trigger and VETO systems data. The K⁴He signals are seen as well as the kaonic carbon (KC), oxygen (KO), nitrogen (KN) and aluminium (KAl) peaks.

Values of the KC, KO, KN and KAl transition energies extracted from the fit of the spectrum above containing the data collected by SIDDHARTINO and SIDDHARTA-2 experiments K⁴He.

References

- [1]. F. Sgaramella et al., Measurements of high-n transitions in intermediate mass kaonic atoms by SIDDHARTA-2 at DAΦNE, EUROPEAN PHYSICAL JOURNAL A 59, 3 (2023).