Abstract
ANAIS (Annual modulation with NaI Scintillators) is a dark matter direct detection experiment consisting of 112.5 kg of NaI(Tl) detectors in operation at the Canfranc Underground Laboratory (LSC), in Spain, since August 2017. ANAIS' goal is to confirm or refute in a model independent way the DAMA/LIBRA positive result: an annual modulation in the low-energy detection rate having all the features expected for the signal induced by dark matter particles in a standard galactic halo. This modulation, observed for about 20 years, is in strong tension with the negative results of other very sensitive experiments, but a model-independent comparison is still lacking. By using the same target material, NaI(Tl), such comparison is more direct and almost independent on dark matter particle and halo models. Here, we present the annual modulation analysis corresponding to three years of ANAIS data (for an effective exposure of 313.95 kg$\times$y), applying a blind procedure which updates that developed for the 1.5 years analysis, and later applied to 2 years. The analysis also improves the background modelling in the fitting of the region of interest rates. We obtain for the best fit in the [1-6] keV ([2-6] keV) energy region a modulation amplitude of -0.0034$\pm$0.0042 cpd/kg/keV (0.0003$\pm$0.0037 cpd/kg/keV), supporting the absence of modulation in our data, and incompatible with DAMA/LIBRA result at 3.3 (2.6) $\sigma$, for a sensitivity of 2.5 (2.7) $\sigma$. Moreover, we include two complementary analyses: a phase-free annual modulation search and the exploration of the possible presence of a periodic signal at other frequencies. Finally, we carry out several consistency checks of our result, and we update the ANAIS-112 projected sensitivity for the scheduled 5 years of operation.
Highlights
Dark matter and dark energy are required to explain the observations of the Universe at different scales if interpreted in the framework of the cosmological standard model
Concerning possible systematic effects which could affect the results presented in this work, we emphasize that our calibration procedure, carried out biweekly and independently for every detector, allows us to correct for any drift or change in the response
The trigger efficiency εtrg(E, d) is calculated from Monte Carlo (MC) simulations, while the efficiencies of the pulse shape cut (εPSA(E, d)) and the asymmetry cut (εasy(E, d)) are evaluated from nonblinded populations accumulated for the whole exposure time: the 3.2 and 0.9 keV events selected by the coincidence with the high energy gammas following 40K and 22Na decays for the pulse shape cut, and 109Cd calibration events for the asymmetry cut
Summary
Dark matter and dark energy are required to explain the observations of the Universe at different scales if interpreted in the framework of the cosmological standard model. With respect to the comparison between ANAIS-112 and DAMA/LIBRA annual modulation results, the corresponding uncertainty would affect the interpretation for those particles producing nuclear recoils in the detector.
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