Whether DAMA’s NaI(Tl) quenching factors differ from recent measurements

Ascertain whether the scintillation quenching factors for sodium and iodine nuclear recoils in the NaI(Tl) crystals used by DAMA/LIBRA differ from the values measured in recent dedicated studies (e.g., by ANAIS and COSINE for Alpha Spectra crystals), in order to ensure a direct, model-independent comparison of energy regions between experiments.

Background

A direct, model-independent comparison of NaI(Tl)-based experiments requires knowledge of the scintillation quenching factors for sodium and iodine nuclear recoils, which map nuclear-recoil energies to electron-equivalent energies. Recent measurements by ANAIS and COSINE suggest energy-independent values around Q_Na ≈ 0.2 and Q_I ≈ 0.06 for Alpha Spectra crystals, in contrast with earlier values often used by DAMA.

If DAMA’s quenching factors differ significantly, comparing the same nominal keVee ranges across experiments may not correspond to the same nuclear-recoil energy intervals, potentially affecting interpretation of the DAMA/ANAIS comparison. The authors explicitly note that the possibility of such a difference remains open and analyze a corresponding shifted energy window to explore the impact.