ANAIS: Status and prospects

TL;DR

ANAIS aims to detect dark matter annual modulation using ultra-pure NaI(Tl) scintillators at LSC, with current results showing promising background levels and sensitivity, and ongoing improvements to detector purity and performance.

Contribution

This paper reports the current status, background performance, and prospects of the ANAIS experiment, including detector radiopurity, threshold reduction, and sensitivity to WIMP signals.

Findings

Detectors achieved radiopurity goals for key isotopes.

Threshold potentially lowered to 1 keVee due to high light collection.

Sensitivity to annual modulation signals demonstrated.

Abstract

ANAIS experiment will look for dark matter annual modulation with large mass of ultra-pure NaI(Tl) scintillators at the Canfranc Underground Laboratory (LSC), aiming to confirm the DAMA/LIBRA positive signal in a model-independent way. Two 12.5 kg each NaI(Tl) crystals provided by Alpha Spectra are currently taking data at the LSC. Present status of ANAIS detectors background and general performance is summarized; in particular, thanks to the high light collection efficiency prospects of lowering the threshold down to 1 keVee are reachable. Crystal radiopurity goals are fulfilled for $^{232}$Th and $^{238}$U chains and $^{40}$K activity, although higher than original goal, could be accepted; however, high $^{210}$Pb contamination out-of-equilibrium has been identified. More radiopure detectors are being built by Alpha Spectra. The ongoing high quantum efficiency PMT tests and muon veto characterization are also presented. Finally, the sensitivity of the experiment for the annual modulation in the WIMP signal, assuming the already achieved threshold and background in ANAIS-25 is shown. Further improvement should be achieved by reducing both threshold and background, as expected.