Bernard Andrieu, Ties Behnke, Philip Bechtle, Xavier Bertou, Jose Busto, Susana Cebrian, Marco Cirelli, Javier De Miguel, Laurent Derome, Cristinel Diaconu, Caterina Doglioni, Guiliana Fiorillo, Davide Franco, Juan Fuster, Romain Gaior, Erika Garutti, Claudio Gatti, B. Gimeno-Martinez, Frederic Girard, Roxanne Guenette, Matthias Hamer, Sophie Henrot-Versille, Thibaut Houdy, Fabrice Hubaut, Adrian Irles, Yoann Kermaidic, Marcin Kuzniak, Axel Lindner, Julien Masbou, Giovanni Mazzitelli, Akira Miyasaki, Enrique Minaya, Konstantinos Nikolopoulos, Federica Petricca, Roman Pöschl, Pascal Pralavorio, Florian Reindl, Leszek Roszkowski, Daniel Santos, Jochen Schieck, Thomas Schoerner, Silvia Scorza, Luca Scotto Lavina, Steinar Stapnes, Achille Stocchi, Maxim Titov, Julia K. Vogel, Masayuki Wada, Jonathan Wilson, Yajing Xing andDirk Zerwas
The search for dark matter is an exciting topic that is pursued in different communities over a wide range of masses and using a variety of experimental approaches. The result is a strongly correlated matrix of activities across Europe and beyond, both on the experimental and the theoretical side. We suggest to encourage and foster the collaboration of the involved institutions on technical, scientific and organisational level, in order to realise the synergies that are required to increase the impact of dark matter research and to cope with the increasing experiment sizes. The suggested network -- loosely titled "DMInfraNet" -- could be realised as a new initiative of the European strategy or be based on existing structures like iDMEu or DRD. The network can also serve as a nucleus for future joint funding proposals.
Julien Billard, Mark Boulay, Susana Cebrián, Laura Covi, Giuliana Fiorillo, Anne Green, Joachim Kopp, Béla Majorovits, Kimberly Palladino, Federica Petricca, Leszek Roszkowski, Marc Schumann
This Report provides an extensive review of the experimental programme of direct detection searches of particle dark matter. It focuses mostly on European efforts, both current and planned, but does it within a broader context of a worldwide activity in the field. It aims at identifying the virtues, opportunities and challenges associated with the different experimental approaches and search techniques. It presents scientific and technological synergies, both existing and emerging, with some other areas of particle physics, notably collider and neutrino programmes, and beyond. It addresses the issue of infrastructure in light of the growing needs and challenges of the different experimental searches. Finally, the Report makes a number of recommendations from the perspective of a long-term future of the field. They are introduced, along with some justification, in the opening Overview and Recommendations section and are next summarised at the end of the Report. Overall, we recommend that the direct search for dark matter particle interactions with a detector target should be given top priority in astroparticle physics, and in all particle physics, and beyond, as a positive measurement will provide the most unambiguous confirmation of the particle nature of dark matter in the Universe.
Iván Coarasa, Julio Amaré, Jaime Apilluelo, Susana Cebrián, David Cintas, Eduardo García, María Martínez, Miguel Ángel Oliván, Ysrael Ortigoza, Alfonso Ortiz de Solórzano, Tamara Pardo, Jorge Puimedón, Ana Salinas, María Luisa Sarsa, Patricia Villar
The ANAIS experiment is intended to search for dark matter annual modulation with ultrapure NaI(Tl) scintillators in order to provide a model independent confirmation or refutation of the long-standing DAMA/LIBRA positive annual modulation signal in the low energy detection rate, using the same target and technique. Other experiments exclude the region of parameters singled out by DAMA/LIBRA. However, these experiments use different target materials, so the comparison of their results depends on the models assumed for the dark matter particle and its distribution in the galactic halo. ANAIS-112, consisting of nine 12.5 kg NaI(Tl) modules produced by Alpha Spectra Inc., disposed in a 3$\times$3 matrix configuration, is taking data smoothly with excellent performance at the Canfranc Underground Laboratory, Spain, since August, 2017. Last published results corresponding to three-year exposure were compatible with the absence of modulation and incompatible with DAMA/LIBRA for a sensitivity above 2.5$σ$ C.L. Present status of the experiment and a reanalysis of the first 3 years data using new filtering protocols based on machine-learning techniques are reported. This reanalysis allows to improve the sensitivity previously achieved for the DAMA/LIBRA signal. Updated sensitivity prospects are also presented: with the improved filtering, testing the DAMA/LIBRA signal at 5$σ$ will be within reach in 2025.
Julio Amaré, Susana Cebrián, Clara Cuesta, Eduardo García, Carlos Ginestra, María Martínez, Miguel A. Oliván, Ysrael Ortigoza, Alfonso Ortíz de Solórzano, Carlos Pobes, Jorge Puimedón, María Luisa Sarsa, José Ángel Villar, Patricia Villar
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.
Iván Coarasa, Julio Amaré, Jaime Apilluelo, Susana Cebrián, David Cintas, Eduardo García, María Martínez, Miguel Ángel Oliván, Ysrael Ortigoza, Alfonso Ortiz de Solórzano, Tamara Pardo, Jorge Puimedón, Ana Salinas, María Luisa Sarsa, Patricia Villar
Apr 26, 2024·astro-ph.IM·PDF Weakly interacting massive particles (WIMPs) are well-motivated candidates for dark matter. One signature of galactic WIMPs is the annual modulation expected in a detector's interaction rate, which arises from Earth's revolution around the Sun. Over two decades, the DAMA/LIBRA experiment has observed such modulation with 250 kg of NaI(Tl) scintillators, in accordance with WIMP expectations but inconsistent with the negative results of other experiments. The signal depends on the target material, so to validate or refute the DAMA result, the experiment must be replicated using the same material. This is the goal of the ANAIS-112 experiment, currently underway since August 2017 with 112.5 kg of NaI(Tl). In this work, we present a reanalysis of three years of data employing an improved analysis chain to enhance the experimental sensitivity. The results presented here are consistent with the absence of modulation and inconsistent with DAMA's observation at nearly 3$σ$ confidence level, with the potential to reach a 5$σ$ level within 8 years from the beginning of the data collection. Additionally, we explore the impact of different scintillation quenching factors in the comparison between ANAIS-112 and DAMA/LIBRA.
Xun Chen, Changbo Fu, Javier Galan, Karl Giboni, Franco Giuliani, Linghui Gu, Ke Han, Xiangdong Ji, Heng Lin, Jianglai Liu, Kaixiang Ni, Hiroki Kusano, Xiangxiang Ren, Shaobo Wang, Yong Yang, Dan Zhang, Tao Zhang, Li Zhao, Xiangming Sun, Shouyang Hu, Siyu Jian, Xinglong Li, Xiaomei Li, Hao Liang, Huanqiao Zhang, Mingrui Zhao, Jing Zhou, Yajun Mao, Hao Qiao, Siguang Wang, Ying Yuan, Meng Wang, Amir N. Khan, Neill Raper, Jian Tang, Wei Wang, Jianing Dong, Changqing Feng, Chen Li, Jianbei Liu, Shubin Liu, Xiaolian Wang, Danyang Zhu, Juan F. Castel, Susana Cebrián, Theopisti Dafni, Javier G. Garza, Igor G. Irastorza, Francisco J. Iguaz, Gloria Luzón, Hector Mirallas, Stephan Aune, Eric Berthoumieux, Yann Bedfer, Denis Calvet, Nicole d'Hose, Alain Delbart, Maria Diakaki, Esther Ferrer-Ribas, Andrea Ferrero, Fabienne Kunne, Damien Neyret, Thomas Papaevangelou, Franck Sabatié, Maxence Vanderbroucke, Andi Tan, Wick Haxton, Yuan Mei, Chinorat Kobdaj, Yu-Peng Yan
Searching for the Neutrinoless Double Beta Decay (NLDBD) is now regarded as the topmost promising technique to explore the nature of neutrinos after the discovery of neutrino masses in oscillation experiments. PandaX-III (Particle And Astrophysical Xenon Experiment III) will search for the NLDBD of $^{136}$Xe at the China Jin Ping underground Laboratory (CJPL). In the first phase of the experiment, a high pressure gas Time Projection Chamber (TPC) will contain 200 kg, 90% $^{136}$Xe enriched gas operated at 10 bar. Fine pitch micro-pattern gas detector (Microbulk Micromegas) will be used at both ends of the TPC for the charge readout with a cathode in the middle. Charge signals can be used to reconstruct tracks of NLDBD events and provide good energy and spatial resolution. The detector will be immersed in a large water tank to ensure $\sim$5 m of water shielding in all directions. The second phase, a ton-scale experiment, will consist of five TPCs in the same water tank, with improved energy resolution and better control over backgrounds.
Julio Amaré, Jaime Apilluelo, Susana Cebrián, David Cintas, Iván Coarasa, Eduardo García, María Martínez, Ysrael Ortigoza, Alfonso Ortiz de Solórzano, Tamara Pardo, Jorge Puimedón, María Luisa Sarsa, Carmen Seoane
The nature of dark matter, which constitutes 27% of the Universe's matter-energy content, remains one of the most challenging open questions in physics. Over the past two decades, the DAMA/LIBRA experiment has reported an annual modulation in the detection rate of $\approx$250 kg of NaI(Tl) detectors operated at the Gran Sasso Laboratory, which the collaboration interprets as evidence of the galactic dark matter detection. However, this claim has not been independently confirmed and is refuted under certain dark matter particle and halo model scenarios. Therefore, it is crucial to perform an experiment with the same target material. The ANAIS experiment uses 112.5 kg of NaI(Tl) detectors at the Canfranc Underground Laboratory and it has been collecting data since August 2017 to model-independently test the DAMA/LIBRA result. This article presents the results of the annual modulation analysis corresponding to six years of ANAIS-112 data. Our results, the most sensitive to date with the same target material, NaI(Tl), are incompatible with the DAMA/LIBRA modulation signal at a 4$σ$ confidence level. Such a discrepancy strongly challenges the DAMA/LIBRA dark matter interpretation and highlights the need to address systematic uncertainties affecting the comparison, particularly those related to the response of detectors to nuclear recoils, which may require further characterization of the DAMA crystals.
Daniel Baxter, Raymond Bunker, Sally Shaw, Shawn Westerdale, Isaac Arnquist, Daniel S. Akerib, Rob Calkins, Susana Cebrián, James B. Dent, Maria Laura di Vacri, Jim Dobson, Daniel Egana-Ugrinovic, Andrew Erlandson, Chamkaur Ghag, Carter Hall, Jeter Hall, Scott Haselschwardt, Eric Hoppe, Chris M. Jackson, Yonatan Kahn, Alvine Kamaha, Mike Kelsey, Alexander Kish, Noah Kurinsky, Matthias Laubenstein, Eric H. Miller, Eric Morrison, Brianna Mount, Jayden L. Newstead, Stefano Nisi, Ibles Olcina, John Orrell, Sergey Pereverzev, Emily Perry, Andreas Piepke, Sagar Sharma Poudel, Karthik Ramanathan, Juergen Reichenbacher, Tarek Saab, Richard Saldanha, Claudio Savarese, Richard Schnee, Silvia Scorza, Rajeev Singh, Kelly Stifter, Burkhant Suerfu, Matthew Szydagis, Dylan J. Temples, Anthony Villano, David Woodward, Jingke Xu
Future dark matter direct detection experiments will reach unprecedented levels of sensitivity. Achieving this sensitivity will require more precise models of signal and background rates in future detectors. Improving the precision of signal and background modeling goes hand-in-hand with novel calibration techniques that can probe rare processes and lower threshold detector response. The goal of this white paper is to outline community needs to meet the background and calibration requirements of next-generation dark matter direct detection experiments.
J. Castel, S. Cebrian, I. Coarasa, T. Dafni, J. Galan, F. J. Iguaz, I. G. Irastorza, G. Luzon, H. Mirallas, A. Ortiz de Solorzano, E. Ruiz-Choliz
Dec 11, 2018·astro-ph.IM·PDF TREX-DM is conceived to look for low-mass Weakly Interacting Massive Particles (WIMPs) using a gas Time Projection Chamber equipped with micromegas readout planes at the Canfranc Underground Laboratory. The detector can hold in the active volume 20 l of pressurized gas up to 10 bar, corresponding to 0.30 kg of Ar or 0.16 kg of Ne. The micromegas are read with a self-triggered acquisition, allowing for thresholds below 0.4 keV (electron equivalent). A low background level in the lowest energy region is another essential requirement. To assess the expected background, all the relevant sources have been considered, including the measured fluxes of gamma radiation, muons and neutrons at the Canfranc Laboratory, together with the activity of most of the components used in the detector and ancillary systems, obtained in a complete assay program. The background contributions have been simulated by means of a dedicated application based on Geant4 and a custom-made code for the detector response. The background model developed for the detector presently installed in Canfranc points to levels from 1 to 10 counts keV-1 kg-1 d-1 in the region of interest, making TREX-DM competitive in the search for low-mass WIMPs. A roadmap to further decrease it down to 0.1 counts keV-1 kg-1 d-1 is underway.
J Amare, S Cebrian, I Coarasa, C Cuesta, E Garcia, M Martinez, M A Olivan, Y Ortigoza, A Ortiz de Solorzano, J Puimedon, A Salinas, M L Sarsa, P Villar, J A Villar
The ANAIS experiment aims at the confirmation of the DAMA/LIBRA signal at the Canfranc Underground Laboratory (LSC). Several 12.5 kg NaI(Tl) modules produced by Alpha Spectra Inc. have been operated there during the last years in various set-ups; an outstanding light collection at the level of 15 photoelectrons per keV, which allows triggering at 1 keV of visible energy, has been measured for all of them and a complete characterization of their background has been achieved. In the first months of 2017, the full ANAIS-112 set-up consisting of nine Alpha Spectra detectors with a total mass of 112.5 kg was commissioned at LSC and the first dark matter run started in August, 2017. Here, the latest results on the detectors performance and measured background from the commissioning run will be presented and the sensitivity prospects of the ANAIS-112 experiment will be discussed.
S. Cebrian, J. Amare, J. M. Carmona, E. Garcia, I. G. Irastorza, G. Luzon, A. Morales, J. Morales, A. Ortiz de Solorzano, J. Puimedon, M. L. Sarsa, J. A. Villar
ANAIS (Annual Modulation with NaI's) is an experiment planned to investigate seasonal modulation effects in the signal of galactic WIMPs using up to 107 kg of NaI(Tl) in the Canfranc Underground Laboratory (Spain). A prototype using one single crystal (10.7 kg) is being developed before the installation of the complete experiment; the first results presented here show an average background level of 1.2 counts/(keV kg day) from threshold (Ethr~4 keV) up to 10 keV.
S. Cebrian
Nov 29, 2023·astro-ph.IM·PDF The production of long-lived radioactive isotopes due to the exposure to cosmic rays on the Earth's surface is an hazard for experiments searching for rare events like the direct detection of galactic dark matter particles. The use of large amounts of liquid Argon is foreseen in different projects, like the DarkSide-20k experiment, intended to look for Weakly Interacting Massive Particles at the Laboratori Nazionali del Gran Sasso. Here, results from the study of the cosmogenic activation of Argon carried out in the context of DarkSide-20k are presented. The induced activity of several isotopes, including 39Ar, and the expected counting rates in the detector have been deduced, considering exposure conditions as realistic as possible.
S. Cebrian
The investigation of rare phenomena requires an effective suppression of all the background components entangling the expected signal. This has compelled the development of a wide range of low radioactivity techniques and background mitigation strategies. Some examples of those applied to Large Time Projection Chambers (TPCs) will be discussed here, including the operation of experiments deep underground, the exhaustive control of material radiopurity and the implementation of discrimination techniques.
J Amare, S Cebrian, D Cintas, I Coarasa, E Garcia, M Martinez, M A Olivan, Y Ortigoza, A Ortiz de Solorzano, J Puimedon, A Salinas, M L Sarsa, P Villar
The ANAIS (Annual modulation with NaI(Tl) Scintillators) experiment aims at the confirmation or refutation of the DAMA/LIBRA positive annual modulation signal in the low energy detection rate. ANAIS-112, consisting of nine 12.5 kg NaI(Tl) modules, is taking data since August, 2017 at the Canfranc Underground Laboratory (LSC) in Spain. Results from the analysis of three years of data are compatible with the absence of modulation. The background model developed for all nine ANAIS-112 detectors was established from commissioning data and non-blinded events in the first year of data taking. Now, background characterization is being improved profiting from the larger accumulated exposure available. Here, the background model is described and comparisons of model and measurements for energy spectra and counting rate time evolution for three-year exposure (considering different analysis conditions) are presented.
T. Dafni, V. Alvarez, I. Bandac, A. Bettini, F. I. G. M. Borges, M. Camargo, S. Carcel, S. Cebrian, A. Cervera, C. A. N. Conde, J. Diaz, R. Esteve, L. M. P. Fernandes, M. Fernandez, P. Ferrario, A. L. Ferreira, E. D. C. Freitas, V. M. Gehman, A. Goldschmidt, H. Gomez, J. J. Gomez-Cadenas, D. Gonzalez-Diaz, R. M. Gutierrez, J. Hauptman, J. A. Hernando Morata, D. C. Herrera, F. J. Iguaz, I. G. Irastorza, L. Labarga, A. Laing, I. Liubarsky, D. Lorca, M. Losada, G. Luzon, A. Mari, J. Martin-Albo, A. Martinez, G. Martinez-Lema, T. Miller, F. Monrabal, M. Monserrate, C. M. B. Monteiro, F. J. Mora, L. M. Moutinho, J. Munoz Vidal, M. Nebot-Guinot, D. Nygren, C. A. B. Oliveira, J. Perez, J. L. Perez Aparicio, J. Renner, L. Ripoll, A. Rodriguez, J. Rodriguez, F. P. Santos, J. M. F. dos Santos, L. Segui, L. Serra, D. Shuman, A. Simon, C. Sofka, M. Sorel, J. F. Toledo, J. Torrent, Z. Tsamalaidze, J. F. C. A. Veloso, J. A. Villar, R. C. Webb, J. T. White, N. Yahlali
The 'Neutrino Experiment with a Xenon TPC (NEXT)', intended to investigate neutrinoless double beta decay, requires extremely low background levels. An extensive material screening and selection process to assess the radioactivity of components is underway combining several techniques, including germanium gamma-ray spectrometry performed at the Canfranc Underground Laboratory; recent results of this material screening program are presented here.
S. Cebrián, J. Pérez, I. Bandac, L. Labarga, V. Álvarez, A. I. Barrado, A. Bettini, F. I. G. M. Borges, M. Camargo, S. Cárcel, A. Cervera, C. A. N. Conde, E. Conde, T. Dafni, J. Díaz, R. Esteve, L. M. P. Fernandes, M. Fernández, P. Ferrario, E. D. C. Freitas, L. M. P. Fernandes, V. M. Gehman, A. Goldschmidt, J. J. Gómez-Cadenas, D. González-Díaz, R. M. Gutiérrez, J. Hauptman, J. A. Hernando Morata, D. C. Herrera, I. G. Irastorza, A. Laing, I. Liubarsky, N. López-March, D. Lorca, M. Losada, G. Luzón, A. Marí, J. Martín-Albo, A. Martínez, G. Martínez-Lema, T. Miller, F. Monrabal, M. Monserrate, C. M. B. Monteiro, F. J. Mora, L. M. Moutinho, J. Muñoz Vidal, M. Nebot-Guinot, D. Nygren, C. A. B. Oliveira, A. Ortiz de Solórzano, J. L. Pérez Aparicio, M. Querol, J. Renner, L. Ripoll, J. Rodríguez, F. P. Santos, J. M. F. dos Santos, L. Serra, D. Shuman, A. Simón, C. Sofka, M. Sorel, J. F. Toledo, J. Torrent, Z. Tsamalaidze, J. F. C. A. Veloso, J. A. Villar, R. C. Webb, J. T. White, N. Yahlali
The Neutrino Experiment with a Xenon TPC (NEXT), intended to investigate the neutrinoless double beta decay using a high-pressure xenon gas TPC filled with Xe enriched in 136Xe at the Canfranc Underground Laboratory in Spain, requires ultra-low background conditions demanding an exhaustive control of material radiopurity and environmental radon levels. An extensive material screening process is underway for several years based mainly on gamma-ray spectroscopy using ultra-low background germanium detectors in Canfranc but also on mass spectrometry techniques like GDMS and ICPMS. Components from shielding, pressure vessel, electroluminescence and high voltage elements and energy and tracking readout planes have been analyzed, helping in the final design of the experiment and in the construction of the background model. The latest measurements carried out will be presented and the implication on NEXT of their results will be discussed. The commissioning of the NEW detector, as a first step towards NEXT, has started in Canfranc; in-situ measurements of airborne radon levels were taken there to optimize the system for radon mitigation and will be shown too.
DarkSide-20k Collaboration
Jan 30, 2023·astro-ph.IM·PDF The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating gamma/beta background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods.
J. Amare, S. Borjabad, S. Cebrian, C. Cuesta, D. Fortuno, E. Garcia, C. Ginestra, H. Gomez, D. C. Herrera, M. Martinez, M. A. Olivan, Y. Ortigoza, A. Ortiz de Solorzano, C. Pobes, J. Puimedon, M. L. Sarsa, J. A. Villar, P. Villar
Samples from different materials typically used as optical windows or light guides in scintillation detectors were studied in a very low background environment, at the Canfranc Underground Laboratory, searching for scintillation. A positive result can be confirmed for natural quartz: two distinct scintillation components have been identified, not being excited by an external gamma source. Although similar effect has not been observed neither for synthetic quartz nor for methacrylate, a fast light emission excited by intense gamma flux is evidenced for all the samples in our measurements. These results could affect the use of these materials in low energy applications of scintillation detectors requiring low radioactive background conditions, as they entail a source of background.
J. Amare, S. Cebrian, C. Cuesta, E. Garcia, C. Ginestra, M. Martinez, M. A. Olivan, Y. Ortigoza, A. Ortiz de Solorzano, C. Pobes, J. Puimedon, M. L. Sarsa, J. A. Villar, P. Villar
The cosmogenic production of long-lived radioactive isotopes in materials is an hazard for experiments demanding ultra-low background conditions. Although NaI(Tl) scintillators have been used in this context for a long time, very few activation data were available. We present results from two 12.5 kg NaI(Tl) detectors, developed within the ANAIS project and installed at the Canfranc Underground Laboratory. The prompt data taking starting made possible a reliable quantification of production of some I, Te and Na isotopes with half-lives larger than ten days. Initial activities underground were measured and then production rates at sea level were estimated following the history of detectors; a comparison of these rates with calculations using typical cosmic neutron flux at sea level and a selected description of excitation functions was also carried out. After including the contribution from the identified cosmogenic products in the detector background model, we found that the presence of 3H in the crystal bulk would help to fit much better our background model and experimental data. We have analyzed the cosmogenic production of 3H in NaI, and although precise quantification has not been attempted, we can conclude that it could imply a very relevant contribution to the total background below 15 keV in NaI detectors.
S. Cebrian, J. Amare, J. M. Carmona, E. Garcia, I. G. Irastorza, G. Luzon, A. Morales, J. Morales, A. Ortiz de Solorzano, J. Puimedon, M. L. Sarsa, J. A. Villar
The present status of the ANAIS experiment (Annual Modulation with NaI's) is shown. ANAIS is intended to use more than 100 kg of NaI(Tl) in the Canfranc Underground Laboratory (Spain) searching for seasonal modulation effects in the WIMP signal; in a first stage, a prototype (one single 10.7 kg crystal) has been developed in order to obtain the best conditions regarding the energy threshold and the radioactive background in the low energy region as well as to check the stability of the environmental conditions. The first results corresponding to an exposure of 2069.85 kg day show an average background level of 1.2 counts/(keV kg day) from threshold ($E_{thr} \sim 4$ keV, even using one single photomultiplier) up to 10 keV.