Improvement and assessment of the radiopurity of Micromegas readout planes

Juan Castel, Susana Cebrian, Theopisti Dafni, David Diez-Ibanez, Alvaro Ezquerro, Juan Antonio Garcia, Hector Gomez, Igor G. Irastorza, Gloria Luzon, Cristina Margalejo, Hector Mirallas, Luis Obis, Rui de Oliveira, Alfonso Ortiz de Solorzano, Oscar Perez, Jorge Porron, Maria J. Puyuelo, Ana Quintana, Maria Rodriguez, Laura Segui

Micromesh Gas Structures (Micromegas) as readout of gaseous Time Projection Chambers (TPCs) are being considered in experiments investigating rare phenomena, like the nuclear double beta decay, solar axion detection and low-mass dark matter interactions, due to their good performance on spatial and energy resolution and operation stability. In addition, as they are potentially made mainly of radiopure materials like copper and kapton, they are appropriate for ultra-low background conditions. After a promising first study of the radiopurity of Micromegas readout planes, here results after dedicated development at CERN obtained from new radioassays, performed at the Canfranc Underground Laboratory combining different techniques, are presented. Activity of the isotopes in the lower parts of the 238U and 232Th natural chains has been constrained by analyzing the BiPo sequences using the BiPo-3 detector to be <0.064 and <0.016 muBq/cm2 respectively, while a lowest 40K content of 0.102+-0.030 muBq/cm2 has been determined by gamma spectroscopy using a HPGe detector; the latter value implies a reduction of a factor 34 with respect to the 40K activity quantified in the first analyzed sample. These results confirm the suitability of the use of Micromegas as extremely radiopure readouts for rare event searches.

Double Beta Decay Experiments at Canfranc Underground Laboratory

Susana Cebrian

The first activities of the Canfranc Underground Laboratory ("Laboratorio Subterráneo de Canfranc", LSC) started in the mid-eighties in a railway tunnel located under the Spanish Pyrenees; since then, it has become an international multidisciplinary facility equipped with different services for underground science. The research activity at LSC is about Astroparticle Physics, dark matter searches and neutrino Physics; but also activities in Nuclear Astrophysics, Geophysics, and Biology are carried out. The investigation of the neutrinoless double beta decay has been one of the main research lines of LSC since the beginning. Many unknowns remain in the characterization of the basic neutrino properties and the study of this rare decay process requiring Physics beyond the Standard Model of Particle Physics can shed light on the lepton number conservation, the nature of the neutrinos as Dirac or Majorana particles and the absolute scale and ordering of the masses of the three generations. Here, the double beta decay searches performed at LSC for different emitters and following very different experimental approaches will be reviewed: from the very first experiments in the laboratory including the successful IGEX for $^{76}$Ge, which released very stringent limits to the effective neutrino mass at the time, to the present NEXT experiment for $^{136}$Xe and future project CROSS ("Cryogenic Rare-event Observatory with Surface Sensitivity") for $^{130}$Te and $^{100}$Mo, both implementing innovative detector technologies to discriminate backgrounds. For the neutrinoless double beta decay channel and at 90% C.L., IGEX derived a limit to the half-life of $^{76}$Ge of $T_{1/2}^{0ν} > 1.57 \times 10^{25}$ y while the corresponding expected limits are $T_{1/2}^{0ν} > 1.0\times 10^{26}$ y for $^{136}$Xe from NEXT-100 (for an exposure of 500 kg.y) and $T_{1/2}^{0ν} > 2.8 \times 10^{25}$ y for $^{100}$Mo from CROSS (for 5 y and 4.7 kg of isotope). Activities related to double beta decays searches carried out in other underground laboratories have also been developed at LSC and will be presented too, like the operation of the BiPo-3 detector for radiopurity measurements of thin sheets with very high sensitivity. For each one of these experiments, the concept, the experimental set-ups and relevant results will be discussed.

Cosmogenic activation in double beta decay experiments

Susana Cebrian

Double beta decay is a very rare nuclear process and, therefore, experiments intended to detect it must be operated deep underground and in ultra-low background conditions. Long-lived radioisotopes produced by the previous exposure of materials to cosmic rays on the Earth's surface or even underground can become problematic for the required sensitivity. Here, the studies developed to quantify and reduce the activation yields in detectors and materials used in the set-up of these experiments will be reviewed, considering target materials like germanium, tellurium and xenon together with other ones commonly used like copper, lead, stainless steel or argon. Calculations following very different approaches and measurements from irradiation experiments using beams or directly cosmic rays will be considered for relevant radioisotopes. The effect of cosmogenic activation in present and future double beta decay projects based on different types of detectors will be analyzed too.

The role of small scale experiments in the direct detection of dark matter

Susana Cebrian

In the direct detection of the galactic dark matter, experiments using cryogenic solid-state detectors or noble liquids play for years a very relevant role, with increasing target mass and more and more complex detection systems. But smaller projects, based on very sensitive, advanced detectors following new technologies, could help in the exploration of the different proposed dark matter scenarios too. There are experiments focused on the observation of distinctive signatures of dark matter, like an annual modulation of the interaction rates or the directionality of the signal; other ones are intended to specifically investigate low mass dark matter candidates or particular interactions. For this kind of dark matter experiments at small scale, the physics case will be discussed and selected projects will be described, summarizing the basics of their detection methods and presenting their present status, recent results and prospects.

Review on dark matter searches

Susana Cebrián

Dark matter particles populating our galactic halo could be directly detected by measuring their scattering off target nuclei or electrons in a suitable detector. As this interaction is expected to occur with very low probability and would generate very small energy deposits, the detection is challenging; the possible identification of distinctive signatures (like an annual modulation in the interaction rates or directionality) to assign a dark matter origin to a possible observation is being considered. Here, the physics case of different dark matter direct detection experiments will be presented and the different and complementary techniques which are being applied or considered will be discussed, summarizing their features and latest results obtained. Special focus will be made on TPC-related projects; experiments using noble liquids have presently a leading role to constrain interaction cross sections of a wide range of dark matter candidates and gaseous detectors are very promising to explore specifically low mass dark matter as well as to measure directionality.

Small scale direct dark matter search experiments

Susana Cebrián

Experiments based on noble liquids and solid state cryogenic detectors have had a leading role in the direct detection of dark matter. But smaller scale projects can help to explore the new dark matter landscape with advanced, ultra-sensitive detectors based on recently developed technologies. Here, the physics case of different types of small scale dark matter experiments will be presented and many of them will be reviewed, highlighting the detection techniques and summarizing their properties, results and status.

Cosmogenic activation of materials

Susana Cebrian

Experiments looking for rare events like the direct detection of dark matter particles, neutrino interactions or the nuclear double beta decay are operated deep underground to suppress the effect of cosmic rays. But the production of radioactive isotopes in materials due to previous exposure to cosmic rays is an hazard when ultra-low background conditions are required. In this context, the generation of long-lived products by cosmic nucleons has been studied for many detector media and for other materials commonly used. Here, the main results obtained on the quantification of activation yields on the Earth's surface will be summarized, considering both measurements and calculations following different approaches. The isotope production cross sections and the cosmic ray spectrum are the two main ingredients when calculating this cosmogenic activation; the different alternatives for implementing them will be discussed. Activation that can take place deep underground mainly due to cosmic muons will be briefly commented too. Presently, the experimental results for the cosmogenic production of radioisotopes are scarce and discrepancies between different calculations are important in many cases, but the increasing interest on this background source which is becoming more and more relevant can help to change this situation.

Searching for WIMPs with TREX-DM: achievements and challenges

Juan F. Castel, Susana Cebrián, Theopisti Dafni, David Díez-Ibáñez, Álvaro Ezquerro, Javier Galán, Juan Antonio García, Igor G. Irastorza, María Jiménez, Gloria Luzón, Cristina Margalejo, Ángel de Mira, Hector Mirallas, Luis Obis, Alfonso Ortiz de Solórzano, Oscar Pérez, Jaime Ruz, Julia Vogel

The TREX-DM detector, a low background chamber with microbulk Micromegas readout, was commissioned in the underground laboratory of Canfranc (LSC) in 2018. Since then, data taking campaigns have been carried out with Argon and Neon mixtures, at different pressures from 1 to 4 bar. By achieving a low energy threshold of 1 keV$_{ee}$ and a background level of 80 counts keV$^{-1}$ Kg$^{-1}$ day$^{-1}$ in the region from 1 to 7 keV$_{ee}$, the experiment demonstrates its potential to search for low-mass WIMPs. Two of the most important challenges currently faced are the reduction of both, background level and energy threshold. With respect to the energy threshold, recently a new readout plane is being developed, based on the combination of Micromegas and GEM technologies, aiming to have a pre-amplification stage that would permit very low energy thresholds, close to the single-electron ionization energy. With respect to the background reduction, apart from studies to identify and minimize contamination population, a high sensitivity alpha detector is being developed in order to allow a proper material selection for the TREX-DM detector components. Both challenges, together with the optimization of the gas mixture used as target for the WIMP detection, will take TREX-DM to explore regions of WIMP's mass below 1 GeV c$^{-2}$.

Report of the Topical Group on Particle Dark Matter for Snowmass 2021

Jodi Cooley, Tongyan Lin, W. Hugh Lippincott, Tracy R. Slatyer, Tien-Tien Yu, Daniel S. Akerib, Tsuguo Aramaki, Daniel Baxter, Torsten Bringmann, Ray Bunker, Daniel Carney, Susana Cebrián, Thomas Y. Chen, Priscilla Cushman, C. E. Dahl, Rouven Essig, Alden Fan, Richard Gaitskell, Cristano Galbiati, Graciela B. Gelmini, Graham K. Giovanetti, Guillaume Giroux, Luca Grandi, J. Patrick Harding, Scott Haselschwardt, Lauren Hsu, Shunsaku Horiuchi, Yonatan Kahn, Doojin Kim, Geon-Bo Kim, Scott Kravitz, V. A. Kudryavtsev, Noah Kurinsky, Rafael F. Lang, Rebecca K. Leane, Benjamin V. Lehmann, Cecilia Levy, Shengchao Li, Ben Loer, Aaron Manalaysay, C. J Martoff, Gopolang Mohlabeng, M. E. Monzani, Alexander St J. Murphy, Russell Neilson, Harry N. Nelson, Ciaran A. J. O'Hare, K. J. Palladino, Aditya Parikh, Jong-Chul Park, Kerstin Perez, Stefano Profumo, Nirmal Raj, Brandon M. Roach, Tarek Saab, Maria Luísa Sarsa, Richard Schnee, Sally Shaw, Seodong Shin, Kuver Sinha, Kelly Stifter, Aritoki Suzuki, M. Szydagis, Tim M. P. Tait, Volodymyr Takhistov, Yu-Dai Tsai, S. E. Vahsen, Edoardo Vitagliano, Philip von Doetinchem, Gensheng Wang, Shawn Westerdale, David A. Williams, Xin Xiang, Liang Yang

This report summarizes the findings of the CF1 Topical Subgroup to Snowmass 2021, which was focused on particle dark matter. One of the most important scientific goals of the next decade is to reveal the nature of dark matter (DM). To accomplish this goal, we must delve deep, to cover high priority targets including weakly-interacting massive particles (WIMPs), and search wide, to explore as much motivated DM parameter space as possible. A diverse, continuous portfolio of experiments at large, medium, and small scales that includes both direct and indirect detection techniques maximizes the probability of discovering particle DM. Detailed calibrations and modeling of signal and background processes are required to make a convincing discovery. In the event that a candidate particle is found through different means, for example at a particle collider, the program described in this report is also essential to show that it is consistent with the actual cosmological DM. The US has a leading role in both direct and indirect detection dark matter experiments -- to maintain this leading role, it is imperative to continue funding major experiments and support a robust R\&D program.

Progress in End-to-End Optimization of Detectors for Fundamental Physics with Differentiable Programming

Max Aehle, Lorenzo Arsini, R. Belén Barreiro, Anastasios Belias, Florian Bury, Susana Cebrian, Alexander Demin, Jennet Dickinson, Julien Donini, Tommaso Dorigo, Michele Doro, Nicolas R. Gauger, Andrea Giammanco, Lindsey Gray, Borja S. González, Verena Kain, Jan Kieseler, Lisa Kusch, Marcus Liwicki, Gernot Maier, Federico Nardi, Fedor Ratnikov, Ryan Roussel, Roberto Ruiz de Austri, Fredrik Sandin, Michael Schenk, Bruno Scarpa, Pedro Silva, Giles C. Strong, Pietro Vischia

In this article we examine recent developments in the research area concerning the creation of end-to-end models for the complete optimization of measuring instruments. The models we consider rely on differentiable programming methods and on the specification of a software pipeline including all factors impacting performance -- from the data-generating processes to their reconstruction and the extraction of inference on the parameters of interest of a measuring instrument -- along with the careful specification of a utility function well aligned with the end goals of the experiment. Building on previous studies originated within the MODE Collaboration, we focus specifically on applications involving instruments for particle physics experimentation, as well as industrial and medical applications that share the detection of radiation as their data-generating mechanism.

The Darkside-20k Data Acquisition System

Fabio Acerbi, Pushparaj Adhikari, Paolo Agnes, Iftikhar Ahmad, Sebastiano Albergo, Ivone F. M. Albuquerque, Thomas Olling Alexander, Andrew Knight Alton, Pierre-Andre Amaudruz, Gioacchino Alex Anastasi, Michele Angiolilli, Elena Aprile, David J. Auty, Maximo Ave Pernas, Oscar Azzolini, Henning Olling Back, Zoe Balmforth, Ana Isabel Barrado Olmedo, Pierre Barrillon, Giovanni Batignani, Swadheen Bharat, Pritindra Bhowmick, Sofia Blua, Valerio Bocci, Walter Bonivento, Bianca Bottino, Mark G. Boulay, Titanilla Braun, Andrzej Buchowicz, Severino Bussino, Jose Busto, Matteo Cadeddu, Mariano Cadoni, Roberta Calabrese, Vincenzo Camillo, Alessio Caminata, Nicola Canci, Andrea Capra, Mauro Caravati, Miguel Cardenas-Montes, Nicola Cargioli, Marco Carlini, Paolo Castello, Paolo Cavalcante, Susana Cebrian, Alexander Chepurnov, Sarthak Choudhary, Luisa Cifarelli, Yann Coadou, Ivan Coarasa, Valentina Cocco, Estefania Conde Vilda, Lucia Consiglio, Harrison Coombes, Andre Filipe Ventura Cortez, Barbara S. Costa, Milena Czubak, Saverio D'Auria, Manuel Dionisio Da Rocha Rolo, Alexander Dainty, Giovanni Darbo, Stefano Davini, Riccardo de Asmundis, Sandro De Cecco, Marzio De Napoli, Giulio Dellacasa, Alexander Derbin, Lea Di Noto, Philippe Di Stefano, Daniel Diaz Mairena, Carlo Dionisi, Grigory Dolganov, Francesca Dordei, Aaron Elersich, Emma Ellingwood, Tyler Erjavec, Niamh Fearon, Marta Fernandez Diaz, Luca Ferro, Andrea Ficorella, Giuliana Fiorillo, Dylon Fleming, Paolo Franchini, Davide Franco, Heriques Frandini Gatti, Federico Gabriele, Devidutta Gahan, Cristiano Galbiati, Grzegorz Galinski, Giacomo Gallina, Marco Garbini, Pablo Garcia Abia, Andrzej Gawdzik, Graham Kurt Giovanetti, Alberto Gola, Luca Grandi, Gianfrancesco Grauso, Giovanni Grilli di Cortona, Alexey Grobov, Maxim Gromov, Julian Guerrero Canovas, Marisa Gulino, Samuel Belayneh Habtemariam, Brianne Rae Hackett, Aksel Hallin, Malgorzata Haranczyk, Timothee Hessel, Celin Hidalgo, James Hollingham, Sosuke Horikawa, Jie Hu, Fabrice Hubaut, Daniel Huff, Theo Hugues, Andrea Ianni, Valerio Ippolito, Ako Jamil, Chris Jillings, Rijeesh Keloth, Nikolas Kemmerich, Ashlea Kemp, Kaori Kondo, George Korga, Lucy Kotsiopoulou, Seraphim Koulosousas, Pablo Kunze, Michael Kuss, Marcin Kuzniak, Maciej Kuzwa, Marco La Commara, Michela Lai, Emmanuel Le Guirriec, Elizabeth Leason, Alfiero Leoni, Lance Lidey, John D Lipp, Marcello Lissia, Ludovico Luzzi, Olga Lychagina, Oliver Macfadyen, Janna Machts, Igor Machulin, Szymon Manecki, Ioannis Manthos, Andrea Marasciulli, Stefano Maria Mari, Camillo Mariani, Jelena Maricic, Maria Martinez, Giuseppe Matteucci, Konstantinos Mavrokoridis, Arthur B. McDonald, Luo Meng, Stefano Merzi, Andrea Messina, Radovan Milincic, Graham Miller, Saverio Minutoli, Ankush Mitra, Jocelyn Monroe, Matteo Morrocchi, Abdulrahman Morsy, Valentina Muratova, Michael Murra, Carlo Muscas, Paolo Musico, Rosario Nania, Marzio Nessi, Grzegorz Nieradka, Konstantinos Nikolopoulos, Evangelia Nikoloudaki, Jaroslaw Nowak, Konstantin Olchanski, Andrey Oleinik, Paolo Organtini, Alfonso Ortiz de Solorzano, Anantha Padmanabhan, Marco Pallavicini, Luciano Pandola, Emilija Pantic, Eugenio Paoloni, Danial Papi, Byungju Park, Grzegorz Pastuszak, Giovanni Paternoster, Riccardo Pavarani, Alec Peck, Paolo Attilio Pegoraro, Krzysztof Pelczar, Ramon Perez, Vicente Pesudo, Stefano Piacentini, Noemi Pino, Guillaume Plante, Andrea Pietro Pocar, Stephen Pordes, Pascal Pralavorio, Elettra Preosti, Darren Price, George Prior, Manuel Pronesti, Sebastiana Puglia, Maria Cecilia Queiroga Bazetto, Fabrizio Raffaelli, Francesco Ragusa, Yorck Ramachers, Alejandro Ramirez, Sudikshan Ravinthiran, Marco Razeti, Andrew Lee Renshaw, Aras Repond, Marco Rescigno, Silvia Resconi, Fabrice Retiere, Ash Ritchie-Yates, Angelo Rivetti, Adam Roberts, Conner Roberts, Diego Rodriguez Rodas, Giovanni Rogers, Luciano Romero, Matteo Rossi, Dmitry Rudik, James Runge, Maria Adriana Sabia, Camilla Salerno, Paolo Salomone, Simone Sanfilippo, Daria Santone, Roberto Santorelli, Edivaldo M. Santos, Isobel Sargeant, Maria Luisa Sarsa, Claudio Savarese, Eugenio Scapparone, Fred Schuckman, Dmitriy Semenov, Carmen Seoane, Michela Sestu, Veronika Shalamova, Sanjay Sharma Poudel, Marino Simeone, Peter Skensved, Mikhail Skorokhvatov, Taisiia Smirnova, Ben Smith, Robert Smith, Franco Spadoni, Martin Spangenberg, Arianna Steri, Vincenzo Stornelli, Simone Stracka, Allan Sung, Clea Sunny, Yury Suvorov, Andrzej M Szelc, Oscar Taborda, Benjamin Tam, Roberto Tartaglia, Alan Taylor, Jonathan Taylor, Gemma Testera, Kevin Thieme, Angus Thompson, Sebastian Torres-Lara, Alessia Tricomi, Sara Tullio, Evgeniy Unzhakov, Marie Van Uffelen, Pedro Ventura, Guillermo Vera Diaz, Simon Viel, Alina Vishneva, Bruce Vogelaar, Joost Vossebeld, Bansari Vyas, Masayuki Wada, Marek Bohdan Walczak, Yi Wang, Shawn Westerdale, Laurie Williams, Marcin Marian Wojcik, Mariusz Wojcik, Changgen Yang, Jilong Yin, Azam Zabihi, Paul Zakhary, Andrea Zani, Haoxiang Zhan, Yongpeng Zhang, Antonino Zichichi, Grzegorz Zuzel

REST-for-Physics, a ROOT-based framework for event oriented data analysis and combined Monte Carlo response

Konrad Altenmüller, Susana Cebrián, Theopisti Dafni, David Díez-Ibáñez, Javier Galán, Javier Galindo, Juan Antonio García, Igor G. Irastorza, Gloria Luzón, Cristina Margalejo, Hector Mirallas, Luis Obis, Oscar Pérez, Ke Han, Kaixiang Ni, Yann Bedfer, Barbara Biasuzzi, Esther Ferrer-Ribas, Damien Neyret, Thomas Papaevangelou, Cristian Cogollos, Eduardo Picatoste

The REST-for-Physics (Rare Event Searches Toolkit for Physics) framework is a ROOT-based solution providing the means to process and analyze experimental or Monte Carlo event data. Special care has been taken on the traceability of the code and the validation of the results produced within the framework, together with the connectivity between code and data stored registered through specific version metadata members. The framework development was originally motivated to cover the needs at Rare Event Searches experiments (experiments looking for phenomena having extremely low occurrence probability like dark matter or neutrino interactions or rare nuclear decays), and its components naturally implement tools to address the challenges in these kinds of experiments; the integration of a detector physics response, the implementation of signal processing routines, or topological algorithms for physical event identification are some examples. Despite this specialization, the framework was conceived thinking in scalability, and other event-oriented applications could benefit from the data processing routines and/or metadata description implemented in REST, being the generic framework tools completely decoupled from dedicated libraries. REST-for-Physics is a consolidated piece of software already serving the needs of different physics experiments - using gaseous Time Projection Chambers (TPCs) as detection technology - for background data analysis and detector characterization, as well as generic detector R\&D. Even though REST has been exploited mainly with gaseous TPCs, the code could be easily applied or adapted to other detection technologies. We present in this work an overview of REST-for-Physics, providing a broad perspective to the infrastructure and organization of the project as a whole. The framework and its different components will be described in the text.

Light Collection in the Prototypes of the ANAIS Dark Matter Project

Julio Amaré, Susana Cebrián, Clara Cuesta, Eduardo García, María Martínez, Miguel A. Oliván, Ysrael Ortigoza, Alfonso Ortíz de Solórzano, Carlos Pobes, Jorge Puimedón, María Luisa Sarsa, José Ángel Villar, Patricia Villar

The ANAIS experiment aims at the confirmation of the DAMA/LIBRA signal using the same target and technique at the Canfranc Underground Laboratory (LSC) in Spain. ANAIS detectors consist of large NaI crystals coupled to two photomultipliers (PMTs). In this work we present Single Electron Response (SER) data for several units of the Hamamatsu R12669SEL2 PMT model extracted from normal operation data of ANAIS underground prototypes and we compare them with PMT SER characterization previously done at surface lab before coupling them to NaI crystal. Moreover, total light collection for different ANAIS prototypes has been calculated, producing an excellent average result of 15 phe/keV, which has a good impact in both energy resolution and threshold.

Radiopurity control in the NEXT-100 double beta decay experiment: procedures and initial measurements

V. Alvarez, I. Bandac, A. Bettini, F. I. G. M. Borges, S. Carcel, J. Castel, S. Cebrian, A. Cervera, C. A. N. Conde, T. Dafni, T. H. V. T. Dias, J. Diaz, M. Egorov, R. Esteve, P. Evtoukhovitch, L. M. P. Fernandes, P. Ferrario, A. L. Ferreira, E. D. C. Freitas, V. M. Gehman, A. Gil, 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, M. A. Jinete, L. Labarga, A. Laing, I. Liubarsky, J. A. M. Lopes, D. Lorca, M. Losada, G. Luzon, A. Mari, J. Martin-Albo, A. Martinez, T. Miller, A. Moiseenko, F. Monrabal, C. M. B. Monteiro, F. J. Mora, L. M. Moutinho, J. Munoz Vidal, H. Natal da Luz, G. Navarro, M. Nebot, D. Nygren, C. A. B. Oliveira, A. Ortiz de Solorzano, R. Palma, 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, A. Tomas, J. Torrent, Z. Tsamalaidze, D. Vazquez, J. F. C. A. Veloso, J. A. Villar, R. C. Webb, J. T. White, N. Yahlali

The Neutrino Experiment with a Xenon TPC (NEXT) is intended to investigate the neutrinoless double beta decay of 136Xe, which requires a severe suppression of potential backgrounds. An extensive screening and material selection process is underway for NEXT since the control of the radiopurity levels of the materials to be used in the experimental set-up is a must for rare event searches. First measurements based on Glow Discharge Mass Spectrometry and gamma-ray spectroscopy using ultra-low background germanium detectors at the Laboratorio Subterráneo de Canfranc (Spain) are described here. Activity results for natural radioactive chains and other common radionuclides are summarized, being the values obtained for some materials like copper and stainless steel very competitive. The implications of these results for the NEXT experiment are also discussed.

Analysis of backgrounds for the ANAIS-112 dark matter experiment

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, J. A. Villar, P. Villar

The ANAIS (Annual modulation with NaI(Tl) Scintillators) experiment aims at the confirmation or refutation of theDAMA/LIBRA positive annual modulation signal in the low energy detection rate, using the same target and technique, at the Canfranc Underground Laboratory (LSC) in Spain. ANAIS-112, consisting of nine 12.5 kg NaI(Tl) modules produced by Alpha Spectra Inc. in a 3x3matrix configuration, is taking data smoothly in "dark matter search" mode since August, 2017, after a commissioning phase and operation of the first detectors during the last years in various setups. A large effort has been carried out withinANAIS to characterize the background of sodium iodide detectors, before unblinding the data and performing the first annual modulation analysis. Here, the background models developed for all the nine ANAIS-112 detectors are presented. Measured spectra from threshold to high energy in different conditions are well described by the models based on quantified activities independently estimated following several approaches. In the region from 1 to 6 keVee the measured, efficiency corrected background level is 3.58+-0.02 keV-1 kg-1 day-1; NaI crystal bulk contamination is the dominant background source being 210Pb, 40K, 22Na and 3H contributions the most relevant ones. This background level, added to the achieved 1 keVee analysis threshold (thanks to the outstanding light collection and robust filtering procedures developed), allow ANAIS-112 to be sensitive to the modulation amplitude measured by DAMA/LIBRA, and able to explore at three sigma level in 5 years the WIMP parameter region singled out by this experiment.

Status of the ANAIS Dark Matter Project at the Canfranc Underground Laboratory

J. Amare, S. Cebrian, C. Cuesta, E. Garcia, M. Martinez, M. A. Olivan, Y. Ortigoza, A. Ortiz de Solorzano, C. Pobes, J. Puimedon, M. L. Sarsa, J. A. Villar, P. Villar

The ANAIS experiment aims at the confirmation of the DAMA/LIBRA signal. A detailed analysis of two NaI(Tl) crystals of 12.5 kg each grown by Alpha Spectra will be shown: effective threshold at 1 keVee is at reach thanks to outstanding light collection and robust PMT noise filtering protocols and the measured background is well understood down to 3 keVee, having quantified K, U and Th content and cosmogenic activation in the crystals. A new detector was installed in Canfranc in March 2015 together with the two previous modules and preliminary characterization results will be presented. Finally, the status and expected sensitivity of the full experiment with 112 kg will be reviewed.

Radiopurity assessment of the tracking readout for the NEXT double beta decay experiment

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, A. L. Ferreira, E. D. C. Freitas, 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 Time-Projection Chamber (NEXT) is intended to investigate the neutrinoless double beta decay of 136Xe, which requires a severe suppression of potential backgrounds; therefore, an extensive screening and selection process is underway to control the radiopurity levels of the materials to be used in the experimental set-up of NEXT. The detector design combines the measurement of the topological signature of the event for background discrimination with the energy resolution optimization. Separate energy and tracking readout planes are based on different sensors: photomultiplier tubes for calorimetry and silicon multi-pixel photon counters for tracking. The design of a radiopure tracking plane, in direct contact with the gas detector medium, was specially challenging since the needed components like printed circuit boards, connectors, sensors or capacitors have typically, according to available information in databases and in the literature, activities too large for experiments requiring ultra-low background conditions. Here, the radiopurity assessment of tracking readout components based on gamma-ray spectroscopy using ultra-low background germanium detectors at the Laboratorio Subterraneo de Canfranc (Spain) is described. According to the obtained results, radiopure enough printed circuit boards made of kapton and copper, silicon photomultipliers and other required components, fulfilling the requirement of an overall background level in the region of interest of at most 8 10-4 counts keV-1 kg-1 y-1, have been identified.

Feebly-Interacting Particles:FIPs 2020 Workshop Report

Prateek Agrawal, Martin Bauer, James Beacham, Asher Berlin, Alexey Boyarsky, Susana Cebrian, Xabier Cid-Vidal, David d'Enterria, Albert De Roeck, Marco Drewes, Bertrand Echenard, Maurizio Giannotti, Gian Francesco Giudice, Sergei Gninenko, Stefania Gori, Evgueni Goudzovski, Julian Heeck, Pilar Hernandez, Matheus Hostert, Igor Irastorza, Alexander Izmaylov, Joerg Jaeckel, Felix Kahlhoefer, Simon Knapen, Gordan Krnjaic, Gaia Lanfranchi, Jocelyn Monroe, Verena Martinez-Outschoorn, Jacobo Lopez-Pavon, Silvia Pascoli, Maxim Pospelov, Diego Redigolo, Andreas Ringwald, Oleg Ruchayskiy, Joshua Ruderman, Heather Russell, Jakob Salfeld-Nebgen, Philip Schuster, Mikhail Shaposhnikov, Lesya Shchutska, Jessie Shelton, Yotam Soreq, Yevgeny Stadnik, Joel Swallow, Kohsaku Tobioka, Yu-Dai Tsai

With the establishment and maturation of the experimental programs searching for new physics with sizeable couplings at the LHC, there is an increasing interest in the broader particle and astrophysics community for exploring the physics of light and feebly-interacting particles as a paradigm complementary to a New Physics sector at the TeV scale and beyond. FIPs 2020 has been the first workshop fully dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020. The workshop has gathered together experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities to discuss progress in experimental searches and underlying theory models for FIPs physics, and to enhance the cross-fertilisation across different fields. FIPs 2020 has been complemented by the topical workshop "Physics Beyond Colliders meets theory", held at CERN from 7 June to 9 June 2020. This document presents the summary of the talks presented at the workshops and the outcome of the subsequent discussions held immediately after. It aims to provide a clear picture of this blooming field and proposes a few recommendations for the next round of experimental results.

AlphaCAMM, a Micromegas-based camera for high-sensitivity screening of alpha surface contamination

Konrad Altenmüller, Juan F. Castel, Susana Cebrián, Theopisti Dafni, David Díez-Ibáñez, Javier Galán, Javier Galindo, Juan Antonio García, Igor G. Irastorza, Gloria Luzón, Cristina Margalejo, Hector Mirallas, Luis Obis, Alfonso Ortiz de Solórzano, Oscar Pérez

Surface contamination of $^{222}$Rn progeny from the $^{238}$U natural decay chain is one of the most difficult background contributions to measure in rare event searches experiments. In this work we propose AlphaCAMM, a gaseous chamber read with a segmented Micromegas, for the direct measurement of $^{210}$Pb surface contamination of flat samples. The detection concept exploits the readout capabilities of the Micromegas detectors for the reconstruction of $^{210}$Po alpha tracks to increase the signal-to-background ratio. We report here on the design and realization of a first 26$\times$26 cm$^2$ non-radiopure prototype, with which the detection concept is demonstrated by the use of a new algorithm for the reconstruction of alpha tracks. AlphaCAMM aims for minimum detectable $^{210}$Pb activities of $100$ nBq cm$^{-2}$ and sensitivity upper limits about $60$ nBq cm$^{-2}$ at 95\% of C.L., which requires an intrinsic background level of $5\times10^{-8}$ alphas cm$^{-2}$ s$^{-1}$. We discuss here the prospects to reach these sensitivity goals with a radiopure AlphaCAMM prototype currently under construction.

Analysis of the 40K contamination in NaI(Tl) crystals from different providers in the frame of the ANAIS project

Clara Cuesta, Julio Amaré, Susana Cebrián, 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

NaI(Tl) large crystals are applied in the search for galactic dark matter particles through their elastic scattering off the target nuclei in the detector by measuring the scintillation signal produced. However, energies deposited in the form of nuclear recoils are small, which added to the low efficiency to convert that energy into scintillation, makes that events at or very near the energy threshold, attributed either to radioactive backgrounds or to spurious noise (non-bulk NaI(Tl) scintillation events), can compromise the sensitivity goals of such an experiment. DAMA/LIBRA experiment, using 250 kg NaI(Tl) target, reported first evidence of the presence of an annual modulation in the detection rate compatible with that expected for a dark matter signal just in the region below 6 keVee (electron equivalent energy). In the frame of the ANAIS (Annual modulation with NaI Scintillators) dark matter search project a large and long effort has been carried out in order to understand the origin of events at very low energy in large sodium iodide detectors and develop convenient filters to reject those non attributable to scintillation in the bulk NaI(Tl) crystal. 40K is probably the most relevant radioactive contaminant in the bulk for NaI(Tl) detectors because of its important contribution to the background at very low energy. ANAIS goal is to achieve levels at or below 20 ppb natural potassium. In this paper we will report on our effort to determine the 40K contamination in several NaI(Tl) crystals, by measuring in coincidence between two (or more) of them. Results obtained for the 40K content of crystals from different providers will be compared and prospects of the ANAIS dark matter search experiment will be briefly reviewed.