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Quarkonia dynamics in the QGP with open quantum systems
No full textInternational audienceWe investigate the real-time dynamics of a correlated heavy quarkantiquark pair inside the Quark-Gluon Plasma using new quantum master equations derived from first QCD principles and based on the work of Blaizot & Escobedo [4]. The full equations are directly numerically solved in one-dimension to reduce computing costs and is used to gain insight on the dynamics in both a static and evolving medium following a Björken-like temperature evolution. The effect of the initial state on the dynamics is also studied
Neutrinoless double beta decay search with XENON1T and XENONnT
No full textInternational audienceThe primary goal of the XENON experiment consists in findingthe first direct evidence for the existence of Dark Matter in the Universe via itsscattering with xenon target nuclei in a dual-phase time projection chamber detector.The unprecedented low level of background reached demonstrated this detectortechnology to be suitable also for other exciting rare-events searches among whichthe neutrinoless double beta decay of 136Xe. The discovery of such a process willshed light on another fundamental challenge in physics nowadays about the natureof neutrinos. In this proceeding I will discuss the current status of neutrinoless doublebeta decay of 136Xe search in XENON1T. In the context of the advancement ofthe XENON program, XENONnT is currently collecting its first scientific data inthe underground INFN Laboratori Nazionali del Gran Sasso in Italy. With its targetmass of 5.9 tonnes of liquid xenon and designed with a high level of backgroundreduction, the XENONnT experiment aims to increase the predecessor sensitivity inrare-events searches. In this proceeding I will also report on the ongoing sensitivityprojection studies for neutrinoless double beta decay search in XENONnT
Copper electroplating for background suppression in the NEWS-G experiment
No full textInternational audienceNew Experiments with Spheres-Gas (NEWS-G) is a dark matter direct detection experiment that will operate at SNOLAB (Canada). Similar to other rare-event searches, the materials used in the detector construction are subject to stringent radiopurity requirements. The detector features a 140-cm diameter proportional counter comprising two hemispheres made from commercially sourced 99.99% pure copper. Such copper is widely used in rare-event searches because it is readily available, there are no long-lived Cu radioisotopes, and levels of non-Cu radiocontaminants are generally low. However, measurements performed with a dedicated 210Po alpha counting method using an XIA detector confirmed a problematic concentration of 210Pb in bulk of the copper. To shield the proportional counter’s active volume, a low-background electroforming method was adapted to the hemispherical shape to grow a 500-µm thick layer of ultra-radiopure copper to the detector’s inner surface. In this paper the process is described, which was prototyped at Pacific Northwest National Laboratory (PNNL), USA, and then conducted at full scale in the Laboratoire Souterrain de Modane in France. The radiopurity of the electroplated copper was assessed through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Measurements of samples from the first (second) hemisphere give 68% confidence upper limits of <0.58µBq/kg (<0.24µBq/kg) and <0.26µBq/kg (<0.11µBq/kg) on the 232Th and 238U contamination levels, respectively. These results are comparable to previously reported measurements of electroformed copper produced for other rare-event searches, which were also found to have low concentration of 210Pb consistent with the background goals of the NEWS-G experiment
Centrality dependence of J/ and (2S) production and nuclear modification in p-Pb collisions at 8.16 TeV
No full textInternational audienceThe inclusive production of the J/ψ and ψ(2S) charmonium states is studied as a function of centrality in p-Pb collisions at a centre-of-mass energy per nucleon pair = 8.16 TeV at the LHC. The measurement is performed in the dimuon decay channel with the ALICE apparatus in the centre-of-mass rapidity intervals −4.46 < y< −2.96 (Pb-going direction) and 2.03 < y< 3.53 (p-going direction), down to zero transverse momentum (p). The J/ψ and ψ(2S) production cross sections are evaluated as a function of the collision centrality, estimated through the energy deposited in the zero degree calorimeter located in the Pb-going direction. The p-differential J/ψ production cross section is measured at backward and forward rapidity for several centrality classes, together with the corresponding average 〈p〉 and values. The nuclear effects affecting the production of both charmonium states are studied using the nuclear modification factor. In the p-going direction, a suppression of the production of both charmonium states is observed, which seems to increase from peripheral to central collisions. In the Pb-going direction, however, the centrality dependence is different for the two states: the nuclear modification factor of the J/ψ increases from below unity in peripheral collisions to above unity in central collisions, while for the ψ(2S) it stays below or consistent with unity for all centralities with no significant centrality dependence. The results are compared with measurements in p-Pb collisions at = 5.02 TeV and no significant dependence on the energy of the collision is observed. Finally, the results are compared with theoretical models implementing various nuclear matter effects.[graphic not available: see fulltext
Architecture and performance of the KM3NeT front-end firmware
No full textInternational audienceThe KM3NeT infrastructure consists of two deep-sea neutrino telescopes being deployed in the Mediterranean Sea. The telescopes will detect extraterrestrial and atmospheric neutrinos by means of the incident photons induced by the passage of relativistic charged particles through the seawater as a consequence of a neutrino interaction. The telescopes are configured in a three-dimensional grid of digital optical modules, each hosting 31 photomultipliers. The photomultiplier signals produced by the incident Cherenkov photons are converted into digital information consisting of the integrated pulse duration and the time at which it surpasses a chosen threshold. The digitization is done by means of time to digital converters (TDCs) embedded in the field programmable gate array of the central logic board. Subsequently, a state machine formats the acquired data for its transmission to shore. We present the architecture and performance of the front-end firmware consisting of the TDCs and the state machine
Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at , = 5.02 TeV
No full textInternational audienceJet fragmentation transverse momentum (j) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-k algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The j values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured j distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher j region, while they underestimate the lower j region. The j distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher j values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower j values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.[graphic not available: see fulltext
Antiproliferative properties of scandium exopolysaccharide complexes on several cancer cell lines
No full textInternational audienceAntimetastatic properties on both murine and human osteosarcoma cell lines (POS-1 and KHOS) have been evidenced using exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium. These derivatives had no significant effect on the cell cycle neither a pro-apoptotic effect on osteosarcoma cells. Based on this observation, these EPSs could be employed as new drug delivery systems for therapeutic uses. A theranostic approach, i.e., combination of a predictive biomarker with a therapeutic agent, has been developed notably by combining with true pair of theranostic radionuclides, such as scandium 47Sc/44Sc. However, it is crucial to ensure that, once complexation is done, the biological properties of the vector remain intact, allowing the molecular tropism of the ligand to recognize its molecular target. It is important to assess if the biological properties of EPS evidenced on osteosarcoma cell lines remain when scandium is complexed to the polymers and can be extended to other cancer cell types. Scandium-EPS complexes were thus tested in vitro on human cell lines: MNNG/HOS osteosarcoma, A375 melanoma, A549 lung adenocarcinoma, U251 glioma, MDA231 breast cancer, and Caco2 colon cancer cells. An xCELLigence Real Cell Time Analysis (RTCA) technology assay was used to monitor for 160 h, the proliferation kinetics of the different cell lines. The tested complexes exhibited an anti-proliferative effect, this effect was more effective compared to EPS alone. This increase of the antiproliferative properties was explained by a change in conformation of EPS complexes due to their polyelectrolyte nature that was induced by complexation. Alterations of both growth factor-receptor signaling, and transmembrane protein interactions could be the principal cause of the antiproliferative effect. These results are very promising and reveal that EPS can be coupled to scandium for improving its biological effects and also suggesting that no major structural modification occurs on the ligan
Radioactivity control strategy for the JUNO detector
No full text35 pages, 12 figuresInternational audienceJUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day, therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration to reduce at minimum the impact of natural radioactivity. We describe our efforts for an optimized experimental design, a careful material screening and accurate detector production handling, and a constant control of the expected results through a meticulous Monte Carlo simulation program. We show that all these actions should allow us to keep the background count rate safely below the target value of 10 Hz in the default fiducial volume, above an energy threshold of 0.7 MeV
Développement de la caméra Compton au xénon liquide XEMIS2 pour l'imagerie 3-gamma : études et optimisation des mesures de la lumière de scintillation
No full textThe work described in this thesis is focused on the studies and optimization of scintillation light measurements in an innovative XEnon Medical Imaging System, named XEMIS2, consisting of a liquid xenon Compton camera, designed for low activity small animal 3-gamma imaging. The main objective of XEMIS2 involves the 3D localization of a radiopharmaceutical labeled with a specific radio-nuclide, such as Scandium-44, and the reduction of the administered activity while preserving the image quality. In XEMIS2, the scintillation light mainly provides the gamma-rays interaction time. A set of photomultiplier tubes are distributed around the active volume to measure it. Besides, a self-triggered scintillation light measurement system has been specially developed for XEMIS2 to carry out. The data acquisition prototype has been implemented and qualified in the XEMIS1 under the XEMIS2 operation conditions. The experimental results indicate that the dedicated detection system has a good performance in scintillation light measurement. Furthermore, it is possible to spatially pre-localize the gamma-rays interactions and achieve the virtual fiducialization of the active volume by matching the scintillation signals with the ionization signals through an algorithm on the basis of the light collection map, which contributes to reducing the occupancy of the TPC (Time Projection Chamber) in the context of increasing the injected activity to shorten the exposure time.Les travaux décrits dans cette thèse sont centrés sur les études et l'optimisation des mesures de la lumière de scintillation dans un système d'imagerie médicale innovant, appelée XEMIS2. Il est constitué d'une caméra Compton au xénon liquide, conçue pour une imagerie 3-gamma des petits animaux à faible activité. L'objectif principal de XEMIS2 est la localisation en 3 dimensions d'un radiopharmaceutique marqué avec un radionucléide spécifique, tel que le Scandium-44, et la réduction de l'activité administrée tout en préservant la qualité de l'image. Dans XEMIS2, la lumière de scintillation fournit principalement le temps d'interaction des rayons gamma. Un ensemble de photomultiplicateurs sont répartis autour du volume actif pour le mesurer. En outre, un système de mesure de la lumière de scintillation auto-déclenché a été spécialement développé pour XEMIS2 afin d’effectuer une prise de données continue avec un temps mort électronique négligeable. Le prototype d'acquisition de données a été implémenté et qualifié dans le prototype XEMIS1 en prenant en compte les conditions de fonctionnement propres à XEMIS2. Les résultats expérimentaux indiquent que ce système de détection dédié a de bonnes performances dans la mesure de la lumière de scintillation. De plus, en corrélant les signaux de scintillation avec les signaux d'ionisation par un algorithme sur la base de la carte de collection de lumière, il est possible de pré-localiser spatialement les interactions des photons gamma et ainsi de réaliser la fiducialization virtuelle du volume actif. Ceci contribue à réduire l'occupation de la TPC (Time Projection Chamber) dans le cadre d’une possible augmentation de l’activité injectée afin de raccourcir le temps d'exposition