Annual modulation results from three-year exposure of ANAIS-112

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 modelindependent comparison is still lacking. By using the same target material, NaI(Tl), such a comparison is more direct and almost independent in 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 × y), applying a blind procedure, which updates the one developed for the 1.5 years analysis, and later applied to 2 years. The analysis also improves the background modeling 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 AE 0.0042 cpd=kg=keV (0.0003 AE 0.0037 cpd=kg=keV), supporting the absence of modulation in our data, and incompatible with the DAMA/LIBRA result at 3.3 (2.6) σ, for a sensitivity of 2.5 (2.7) σ. 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.

Scintillation characteristics of a NaI(Tl) crystal at low-temperature with silicon photomultiplier

“…Due to excellent scintillation properties, NaI(Tl) crystals are widely used to measure energies of gammas from environmental radioactivities [1] and from interactions of new physics particles [2][3][4][5][6][7]. In particular, a direct detection of dark matter particles using NaI(Tl) crystal detectors is currently being conducted in several experiments [8][9][10][11].…”

High sensitivity characterization of an ultrahigh purity NaI(Tl) crystal scintillator with the SABRE proof-of-principle detector

“…However, they could not provide a definite answer to the long-standing controversy due to their signal-to-noise ratio diminished by constant radioactive backgrounds several times higher than that observed in the DAMA crystals [16,17]. Large fractions of the backgrounds come from radioactive contaminants in the crystal, most notably 40 K, 210 Pb, and 3 H. As a result, current experiments have to run for many years to obtain the required sensitivity [18]. This also indicates that next-generation experiments using NaI(Tl) crystals with radiopurity similar to or below the DAMA level, such as the proposed SABRE experiment [19], can test the annual modulation claim efficiently in a shorter period of time.…”

Searches for light dark matter using condensed matter systems

“…In this section, we will give a description of the potential DM signal that comes from exciting bound states of a harmonic potential, as a prelude to single or few-phonon excitations in condensed matter systems. 10 The harmonic potential we will work with is given by…”