Proceeding Paper Dark Matter Annual Modulation Results from the ANAIS-112 Experiment † Julio Amaré 1,2, Susana Cebrián 1,2,* , David Cintas 1,2, Iván Coarasa 1,2, Eduardo García 1,2, María Martínez 1,2,3, Miguel Ángel Oliván 1,2,4, Ysrael Ortigoza 1,2, Alfonso Ortiz de Solórzano 1,2, Jorge Puimedón 1,2, Ana Salinas 1,2, María Luisa Sarsa 1,2 and Patricia Villar 1,2 1 Centro de Astropartículas y Física de Altas Energías (CAPA), Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain; [email protected] (J.A.); [email protected] (D.C.); [email protected] (I.C.); [email protected] (E.G.); [email protected] (M.M.); [email protected] (M.Á.O.); [email protected] (Y.O.); [email protected] (A.O.d.S.); [email protected] (J.P.); [email protected] (A.S.); [email protected] (M.L.S.); [email protected] (P.V.) 2 Laboratorio Subterráneo de Canfranc, Paseo de los Ayerbe s.n., Canfranc Estación, 22880 Huesca, Spain 3 Fundación ARAID, Av. de Ranillas 1D, 50018 Zaragoza, Spain 4 Fundación CIRCE, 50018 Zaragoza, Spain * Correspondence: [email protected]; Tel.: +34-976-761-243 † Presented at the 1st Electronic Conference on Universe, 22–28 February 2021; Available online: https://ecu2021.sciforum.net/. Abstract: An annual modulation in the interaction rate of galactic dark matter particles is foreseen due to Earth’s movement around the Sun; the DAMA/LIBRA observation of a modulation signal compatible with expectations has intrigued the community for twenty years. The ANAIS-112 experi- ment, with a target of 112.5 kg of NaI(Tl), has been running smoothly at the Canfranc Underground Laboratory (Spain) since 2017. It aims to test this observation using the same detection technique and · Citation: Amaré, J.; Cebrián, S.; target. Results on the modulation search from two years of data (220.7 kg y) have been presented Cintas, D.; Coarasa, I.; García, E.; and the analysis of three years (313.6 kg·y) is underway. Under the hypothesis of modulation, the Martínez, M.; Oliván, M.Á.; Ortigoza, deduced amplitudes from best fits are in all cases compatible with zero for the two energy regions Y.; de Solórzano, A.O.; Puimedón, J.; at [2–6] and [1–6] keV; the results agree with the expected sensitivity for the considered exposure et al. Dark Matter Annual and fully support the goal of achieving a 3σ sensitivity to explore the DAMA/LIBRA result for a Modulation Results from the five-year operation. Here, the ANAIS-112 set-up and performance will be briefly recapped and the ANAIS-112 Experiment. Phys. Sci. annual modulation results and prospects will be discussed. Forum 2021, 2, 33. https://doi.org/ 10.3390/ECU2021-09331 Keywords: dark matter; WIMPs; direct detection; annual modulation; NaI scintillators Academic Editor: Douglas Singleton Published: 24 February 2021 1. Introduction Publisher’s Note: MDPI stays neutral The direct detection of dark matter particles, such as the so-called weakly interacting with regard to jurisdictional claims in massive particles (WIMPs) which could populate the galactic halo, is mainly based on their published maps and institutional affil- elastic scattering off target nuclei in suitable detectors [1]. As Earth moves around the iations. Sun, the relative velocity between the detector and the dark matter particles follows a time variation, giving rise to a modulation in the expected rate of interaction with well-defined features [2]. The DAMA/LIBRA experiment, based on data with about 250 kg of NaI(Tl) detectors at the Gran Sasso Underground Laboratory in Italy, has reported the presence of an annual modulation signal with all the expected properties at a confidence level of 12.9σ, Copyright: © 2021 by the authors. · Licensee MDPI, Basel, Switzerland. from an exposure of 2.46 t y accumulated over two decades [3,4]. Taking into account This article is an open access article the results presented by other direct detection experiments using different targets (see distributed under the terms and for instance [1]), a tension appears if considering the DAMA/LIBRA signal as due to conditions of the Creative Commons dark matter, assuming common but also more generic interaction or halo models. In this Attribution (CC BY) license (https:// context, to prove or disprove the DAMA/LIBRA observation in a model-independent way, creativecommons.org/licenses/by/ using the same target and technique would be essential; this is the goal of the ANAIS 4.0/). experiment [5]. Other projects all over the world have undertaken this task too, such Phys. Sci. Forum 2021, 2, 33. https://doi.org/10.3390/ECU2021-09331 https://www.mdpi.com/journal/psf Phys. Sci. Forum 2021, 2, 33 2 of 6 Phys. Sci. Forum 2021, 2, 33 2 as COSINE-100 (which is also taking data with first annual modulation results for an exposure of 97.7 kg·y released [6]) while SABRE [7], PICOLON [8] and COSINUS [9] are in preparation. ANAIS experiment [5]. Other projects all over the world have undertaken this task too, such as COSINE-100 (which is also taking data with first annual modulation results for an 2. Experiment exposure of 97.7 kg·y released [6]) while SABRE [7], PICOLON [8] and COSINUS [9] are in preparation. The ANAIS-112 experiment, located at the Canfranc Underground Laboratory (LSC), in Spain, started2. theExperiment data-taking phase in August 2017. A full description of the set-up, shown in Figure1, canThe beANAIS-112 found inexperiment, [ 10]. ANAIS-112 located at the includes Canfranc Underground an array of Laboratory 3 × 3 NaI(Tl) (LSC), scintillators, within Spain, a crystal started mass the data-taking of 12.5 kg phase each in and August a total 2017. massA full ofdescription 112.5 kg. of the ANAIS set-up, detectors were manufacturedshown in Figure by1, can the be Alpha found Spectrain [10]. ANAIS-112 Inc. company includes in an Colorado array of 3 (US)× 3 NaI(Tl) and two Hamamatsuscintillators, photomultipliers with a crystal (PMTs), mass of model12.5 kg each R12669SEL2, and a total mass were of coupled112.5 kg. ANAIS to each de- tectors were manufactured by the Alpha Spectra Inc. company in Colorado (US) and two crystal through quartzHamamatsu windows photomultipliers at the LSC (PMTs), clean model room. R1 The2669SEL2, copper were enclosure coupled hasto each a Mylar crystal window (to performthrough low-energy quartz windows calibration at the LSC using clean external room. The sources) copper enclosure and detectors has a Mylar showed win- an outstandingdow optical (to perform quality; low-energy together calibration with the using high external efficiency sources) of theand PMTsdetectors used, showed this an allowed for the achievementoutstanding optical of a lightquality; collection together with of ~15 the photoelectrons high efficiency of (phe) the PMTs per keVused, for this all al- the detector unitslowed [11]. for The the shielding achievement of of ANAIS-112 a light collection is made of ~15 of photoelectrons 10 cm of archaeological (phe) per keV leadfor all the detector units [11]. The shielding of ANAIS-112 is made of 10 cm of archaeological followed by 20 cm of low-activity lead against the external gamma radiation, a box filled lead followed by 20 cm of low-activity lead against the external gamma radiation, a box with radon-freefilled N2 gas with to radon-free avoid radon N2 gas intrusion to avoid radon being intrusion under being overpressure, under overpressure, and 40 cm and of 40 polyethylene andcm water of polyethylene to moderate and water neutrons. to moderate Sixteen neut plasticrons. Sixteen scintillators plastic scintillators cover the cover sides the and top of the set-upsides and acting top of as the an set-up active acting veto as toan tagactive residual veto to tag muons. residual The muons. LSC The facilities LSC facilities are placed at a depthare of placed 2450 at m.w.e. a depth of 2450 m.w.e. (a) (b) FigureFigure 1. Set-up 1. ofSet-up the ANAIS-112 of the ANAIS-112 experiment: ( experiment:a) Schematic view (a) showing Schematic the nine view modules showing and the the ninefull shielding; modules (b) and Picture taken during ANAIS-112 commissioning with detectors, lead shielding and calibration system visible. the full shielding; (b) Picture taken during ANAIS-112 commissioning with detectors, lead shielding and calibration systemThe visible. ANAIS-112 hardware and software for data acquisition, fine-tuned in the previ- ous operation of several prototypes, were also described in [10]. The PMT electric pulses The ANAIS-112taken hardwarefrom the detectors and software are processed for data for acquisition,trigger and for fine-tuned signals at both in the high previous and low operation of severalenergy. prototypes, The waveform were of alsothe low-energy described signal in [10 is]. recorded The PMT at 2 electricGS/s. For pulses each PMT, taken the from the detectorstrigger are is processed at phe level; for the triggercoincidence and (logical for signals AND) in at a both 200 ns high window and of low the energy.two PMT The waveform ofsignals the low-energy from a module signal gives the is recorded acquisition at trigger. 2 GS/s. Every For two each weeks, PMT, measurements the trigger with is 109Cd sources are made for calibration and correction of potential gain drifts, if necessary. at phe level; the coincidenceAn accurate calibration (logical AND)in the low in aenergy 200 ns range window down of to the the twothreshold PMT is signals performed from by 109 a module gives theconsidering acquisition both trigger.the information Every twofrom weeks,the 109Cd measurements calibration measurements with Cd and sources from 40K are made for calibrationand 22Na emissions and correction from crystal of potentialcontaminations gain corresponding drifts, if necessary.