NEWS-G, Light dark matter search with a Spherical Proportional Counter, First results and Future prospects

International audienceNEWS-G (New Experiments With Spheres-Gas) is an experiment aiming to shine a light on the dark matter conundrum using a novel gaseous detector, the Spherical Proportional Counter. NEWS-G uses light noble gases, such as hydrogen, helium, and neon, as targets, to search for light dark matter down to the sub-GeV/c${}^{2}$ mass region. The first detector of NEWS-G, is a 60 cm diameter sphere already operated in the Underground Laboratory of Modane, while the full-scale detector, 140 cm in diameter, will be installed in SNOLab at the end of this year. In this work, we present the first NEWS-G results with neon as target, which excludes at 90$\%$ confidence level cross-sections above $4.4\cdot 10{}^{37}$ cm${}^{2}$ for a candidate with a mass 0.5 GeV$/$c${}^{2}$ based on 9.7 kg$\cdot$days of exposure. The status of the project and prospects for the future are also discussed

Μελέτη και ανίχνευση χαμηλής ενέργειας νετρίνων

The idea of the detection of low energy neutrinos through the coherent neutrino nucleus elastic scattering intrigues the scientific community for a few decades now but remains unrealized. This interaction is predicted by the Standard Model and is considered advantageous over any other mode because of the sizeable increase of the cross section by a factor of the neutron number squared. Many interesting neutrino sources belong to the low energy category such as Supernova neutrinos, reactor neutrinos, Solar neutrinos and Geoneutrinos, the measurement of which promises new doors opened to fundamental physics, astrophysics and neutrino technologies. Furthermore, the experimental efforts for low energy neutrino measurements are of great interest to experimental research on direct Dark Matter detection. The reason is that they share the similar recoil signature and neutrinos consist the "background floor" of the Dark Matter measurements. But the detection of neutrinos by utilizing this interaction is a great challenge because of the fact that detectors with large target masses are not sensitive to low energy recoils (keV). In this thesis we propose the use of a novel gaseous TPC, the Spherical Proportional Counter (SPC), for low energy neutrino detection and study the conditions to perform such a task. The study can be divided in three parts; the first part is the experimental detection and the measurement of the detector response to low energy nuclear recoils. The low energy recoils are produced inside the gaseous volume of the detector by using neutron sources and exploiting the neutron nucleus elastic scattering. The second part is the development of software for the detailed simulation of radiation interactions with the experimental set up and the detector response to them. GEANT4 code is used to simulate the geometry of the experimental set up, to calculate the ionization yield inside the gaseous volume and to study the shielding response to background radiation. Apart from the GEANT4 simulation, a new method was developed for the calculation of the mean ionization potential and the Fano factor of low energy recoils in a specific medium using the ionization quenching factor calculated with SRIM and experimental data for the electron mean ionization potential and Fano factor of a given medium. The response of the detector to ionizing radiation is simulated with a software developed based on Garfield++. This software is used to simulate all the physical processes involved to the function of the detector like the drift, the diffusion and the multiplication of charges, to produce the output pulse of the electronics. The third part is the development of a code to utilize the fiducialization capabilities of the detector to discriminate localized energy depositions and spatially extended ones, for background rejection. Finally, a new experiment for Supernova neutrino detection is proposed. The set up of which consists of a highly pressurized SPC, placed deep underground for background reduction. The response of this set up to the low energy neutrino spectrum of a Supernova was simulated based on the computational methods developed during this thesis.Η ιδέα της ανίχνευσης χαμηλής ενέργειας νετρίνων μέσω της σύμφωνης ελαστικής σκέδασης νετρίνου πυρήνα ιντριγκάρει την επιστημονική κοινότητα εδώ και δεκαετίες, αλλά ακόμα δεν έχει υλοποιηθεί. Η αλληλεπίδραση αυτή προβλέπεται από το Καθιερωμένο Πρότυπο και θεωρείται υπέρτερη κάθε άλλης αλληλεπιδράσης νετρίνων, λόγω της σημαντικής αύξησης της ενεργού διατομής κατά ένα παράγοντα του νετρονικού αριθμού του πυρήνα στο τετράγωνο (σε σύγκριση με την ελαστική σκέδαση νετρίνου νουκλεονίου). Πολλές ενδιαφέρουσες πηγές ανήκουν σε αυτή την κατηγορία νετρίνων, όπως τα νετρίνα από Υπερκαινοφανείς αστέρες, από πυρηνικούς αντιδραστήρες, Ηλιακά νετρίνα και Γεωνετρίνα. Η ανίχνευση των νετρίνων αυτών θα ανοίξει νέες πόρτες στη στοιχειώδη φυσική, στην αστροφυσική και την τεχνολογία νετρίνων. Επιπλέον οι πειραματικές προσπάθειες για την μέτρηση των νετρίνων χαμηλής ενέργειας είναι σημαντικές και για έναν άλλο τομέα έρευνας, αυτόν της ανίχνευσης Σκοτεινής Ύλης μέσω ελαστικών σκεδάσεων. Η ανίχνευση όμως νετρίνων, εκμεταλλευόμενοι την σύμφωνη ελαστική σκέδαση είναι μια απαιτητική διαδικασία, καθώς οι συνήθεις ανιχνευτές με μεγάλες ενεργές μάζες δεν έχουν ευαισθησία σε ανακρουόμενους πυρήνες με ενέργεια στην περιοχή των keV. Σε αυτή τη διατριβή προτείνεται η χρήση ενός καινοτόμου ανιχνευτή αερίου γεμίσματος, του Σφαιρικού Αναλογικού Απαριθμητή για την ανίχνευση των νετρίνων χαμηλής ενέργειας μέσω της σύμφωνης ελαστικής σκέδασης νετρίνου πυρήνα και μελετώνται η συνθήκες για να περατωθεί ένα τέτοιο έργο. Η μελέτη που έχει γίνει μπορεί να χωριστεί σε τρία μέρη; το πρώτο μέρος είναι η πειραματική ανίχνευση και η μέτρηση της απόκρισης του ανιχνευτή σε χαμηλής ενέργειας ανακρουόμενους πυρήνες. Το δεύτερο κομμάτι είναι η ανάπτυξη λογισμικού για την λεπτομερή περιγραφή της αλληλεπίδρασης ακτινοβολιών με την πειραματική διάταξη και της απόκρισης του ανιχνευτή σε αυτές. Το λογισμικό GEANT4 χρησιμοποιείται για την προσομοίωση της πειραματικής διάταξης και τον υπολογισμό της εναπόθεσης ενέργειας στο αέριο γέμισμα, καθώς και για να μελετηθεί η απόκριση της θωράκισης στις ακτινοβολίες υποβάθρου. Εκτός από την προσομοίωση με το GEANT4, έχει αναπτυχθεί μια καινούργια μέθοδος για τον υπολογισμό της μέσης ενέργειας ιονισμού και του παράγοντα Fano ενός μέσου. Η απόκριση του ανιχνευτή στις ιονιστικές ακτινοβολίες προσομοιώνεται με λογισμικό που έχει αναπτυχθεί βασισμένο στο GARFIELD++. Αυτό το λογισμικό χρησιμοποιείται για να προσομοιωθούν όλες οι φυσικές διαδικασίες που λαμβάνουν χώρα κατά τη λειτουργία του ανιχνευτή, όπως η ολίσθηση, η διάχυση και ο πολλαπλασιασμός των φορτίων, καθώς και η απόκριση των ηλεκτρονικών συστημάτων. Το τρίτο μέρος είναι η ανάπτυξη λογισμικού βασισμένο στην δυνατότητα που μας δίνει ο ανιχνευτής για διάκριση διαφόρων τύπων αλληλεπιδράσεων, μέσω ανάλυσης σχήματος παλμού. Τέλος, προτείνεται η κατασκευή ενός Σφαιρικού Αναλογικού Απαριθμητή, για την ανίχνευση νετρίνων ενός Υπερκαινοφανούς αστέρα. Η πειραματική διάταξη αποτελείται από έναν Σφαιρικό Αναλογικό Αναρίθμητη σε υψηλή πίεση, τοποθετημένο βαθιά κάτω από την γη, για την μείωση του υποβάθρου. Τέλος κάνωντας χρήση των μεθόδων που αναπτύχθηκαν κατά τη διάρκεια της διατριβής, προσομοιώνεται η απόκριση του ανιχνευτή σε ένα φάσμα νετρίνων Υπερκαινοφανούς αστέρα και υπολογίζεται η απόδοση του στην ανίχνευση των νετρίνων αυτών

Ionisation quenching factors from W-values in pure gases for rare event searches

The effect of ionisation quenching for ions is critical for experiments relying on the measurement of low energy recoils, such as direct Dark Matter searches. We present ionisation quenching factor estimates over a range of energies for protons, $\alpha$-particles, and heavier ions in H$_{2}$, CH$_{4}$, N$_{2}$, Ar, CO$_{2}$, and C$_{3}$H$_{8}$ gases, estimated from the respective reference W-value measurements. The resulting ionisation quenching factors are compared with predictions from SRIM.Comment: This work was performed in the context of the NEWS-G experiment. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk\l{}odowska-Curie grant agreement no 841261 (DarkSphere

EXCESS workshop: Descriptions of rising low-energy spectra

International audienceMany low-threshold experiments observe sharply rising event rates of yet unknown origins below a few hundred eV, and larger than expected from known backgrounds. Due to the significant impact of this excess on the dark matter or neutrino sensitivity of these experiments, a collective effort has been started to share the knowledge about the individual observations. For this, the EXCESS Workshop was initiated. In its first iteration in June 2021, ten rare event search collaborations contributed to this initiative via talks and discussions. The contributing collaborations were CONNIE, CRESST, DAMIC, EDELWEISS, MINER, NEWS-G, NUCLEUS, RICOCHET, SENSEI and SuperCDMS. They presented data about their observed energy spectra and known backgrounds together with details about the respective measurements. In this paper, we summarize the presented information and give a comprehensive overview of the similarities and differences between the distinct measurements. The provided data is furthermore publicly available on the workshop’s data repository together with a plotting tool for visualization

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on $10^3$ pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

DUNE Offline Computing Conceptual Design Report

This document describes Offline Software and Computing for the Deep Underground Neutrino Experiment (DUNE) experiment, in particular, the conceptual design of the offline computing needed to accomplish its physics goals. Our emphasis in this document is the development of the computing infrastructure needed to acquire, catalog, reconstruct, simulate and analyze the data from the DUNE experiment and its prototypes. In this effort, we concentrate on developing the tools and systems that facilitate the development and deployment of advanced algorithms. Rather than prescribing particular algorithms, our goal is to provide resources that are flexible and accessible enough to support creative software solutions as HEP computing evolves and to provide computing that achieves the physics goals of the DUNE experiment.This document describes the conceptual design for the Offline Software and Computing for the Deep Underground Neutrino Experiment (DUNE). The goals of the experiment include 1) studying neutrino oscillations using a beam of neutrinos sent from Fermilab in Illinois to the Sanford Underground Research Facility (SURF) in Lead, South Dakota, 2) studying astrophysical neutrino sources and rare processes and 3) understanding the physics of neutrino interactions in matter. We describe the development of the computing infrastructure needed to achieve the physics goals of the experiment by storing, cataloging, reconstructing, simulating, and analyzing $\sim$ 30 PB of data/year from DUNE and its prototypes. Rather than prescribing particular algorithms, our goal is to provide resources that are flexible and accessible enough to support creative software solutions and advanced algorithms as HEP computing evolves. We describe the physics objectives, organization, use cases, and proposed technical solutions

DUNE Offline Computing Conceptual Design Report

This document describes Offline Software and Computing for the Deep Underground Neutrino Experiment (DUNE) experiment, in particular, the conceptual design of the offline computing needed to accomplish its physics goals. Our emphasis in this document is the development of the computing infrastructure needed to acquire, catalog, reconstruct, simulate and analyze the data from the DUNE experiment and its prototypes. In this effort, we concentrate on developing the tools and systems thatfacilitate the development and deployment of advanced algorithms. Rather than prescribing particular algorithms, our goal is to provide resources that are flexible and accessible enough to support creative software solutions as HEP computing evolves and to provide computing that achieves the physics goals of the DUNE experiment

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on $10^3$ pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype