Investigating the E2 nuclear resonance effect in kaonic atoms

Abstract

The nuclear E2 resonance effect occurs when an atomic de-excitation energy is closely matched by a nuclear excitation energy. It produces an attenuation of some of the atomic X-ray lines in the resonant isotope target. Investigating the nuclear E2 resonance effect in kaonic atoms, important information about kaon-nucleus strong interaction can be provided. The only K − − 42 98 Mo nuclear resonance effect was measured by G. L. Goldfrey, G- K. Lum and C. E. Wiegand at Lawrence Berkeley Laboratory, in 1975. The nuclear E2 resonance effect was observed in 25 hours of data taking, not enough to provide a conclusive result. In four kaonic Molybdenum isotopes ( 42 94 Mo , 42 96 Mo , 42 98 Mo and 42 100 Mo ), the nuclear E2 resonance effect is expected at the same transition, with similar energy values. The KAMEO (Kaonic Atoms Measuring nuclear resonance Effects Observables) experiment plans to study the E2 nuclear resonance effect in kaonic Molybdenum isotopes at the DAΦNE e+e− collider, during the SIDDHARTA-2 experiment. The experimental strategy consists of exposing four solid strip targets, each enriched with one Molybdenum isotope, to negatively charged kaons, using a germanium detector for X-ray transition measurements. A further exposure of a non-resonant 42 92 Mo isotope solid strip target will be used as reference for standard non-resonant transitions.

Kaonic atoms at the DAΦNE collider: a strangeness adventure

“…The estimated parameters of the effect can be found in [85]. The KAMEO (Kaonic Atoms Measuring Nuclear Resonance Effects Observables) experiment plans to perform conclusive and precise measurements of the E2 nuclear resonance effects in KMo isotopes ( [43]). We plan to expose to the kaons five solid target strips of enriched Mo isotopes ( > 99%) : 94 42 Mo, 96 42 Mo, 98 42 Mo, 100 42 Mo and 92 42 Mo (the latter used as the reference for standard transition not affected by the E2 nuclear resonance) in order to measure the x-ray transitions with the HPGe detector described in subsection 3.3.…”

“…The MC simulation, in parallel with the analysis of the spectra collected with the HPGe detector during the commissioning phase of DAΦNE, for background evaluation, will allow to estimate the required integrated luminosity for measurements of the effect. Further information about the KAMEO proposal can be found in [43].…”

“…It is the only accepted molecular state ([39]) of the hadron spectrum, and confirmed as 4 "stars" resonances by Particle Data Group since 2021 ([40]). The kaonic atoms measurements provide precise data about K − -N strong interaction at threshold energy, which represents a crucial input for different theoretical approaches below threshold, thus allowing to pin down the characteristics of this exotic state.Further experimental investigations may also have impacts in many fields, from nuclear interaction ([28-30]) to neutron stars ( [31][32][33][34][35][36][41][42][43]): The core of the neutron stars would be populated with particles with strangeness. This hypothesis is being cross-checked with the data extracted by recent astrophysical measurements, including the observation of gravitational waves, that constrain mass and dimensions of the neutron stars ( [44][45][46]).…”