Results of the SDHCAL technological prototype

The SDHCAL technological prototype that has been completed in 2012 was exposed to beams of pions and electrons of different energies at the CERN SPS for a total time period of 5 weeks. The data has been analyzed within the CALICE collaboration. Preliminary results indicate that a highly granular hadronic calorimeter conceived for PFA application is also a powerful tool to separate pions from electrons. The SDHCAL provides also a very good resolution of hadronic showers energy measurement. The use of multi-threshold readout mode shows a clear improvement of the resolution at energies exceeding 30 GeV with respect to the binary readout mode. Simulations of the pion interactions in the SDHCAL are presented and new ideas to improve on the energy resolution using the topology of hadronic showers are mentioned.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS13), Tokyo, Japan, 11-15 November 201

Étude des gerbes hadroniques à l'aide du prototype du calorimètre hadronique semi-digital et comparaison avec les modèles théoriques utilisés dans le logiciel GEANT4

The International Linear Collider ILC is an electron-positron collider project proposed to become the next particle collider after the Large Hadron Collider LHC. This collider will allow to study, in details, the new 125 GeV boson, discovered in 2012 by CMS and ATLAS experiments. This new particle seems compatible with the standard model Higgs boson. The International Collider may also allow physicists to discover new physics. In order to operate this new collider, two collaborations are developing two detectors : the International Large Detector ILD and the Silicon Detector SiD. These general-purpose detectors are optimised for particle flow algorithms. The team from Lyon in which I worked during my Ph.D., has widely participated in the development of the semi-digital hadronic calorimeter SDHCAL. This high granular calorimeter is one option for the International Large Detector hadronic calorimeter. A prototype has been built in 2011. This 1 m3 prototype is made of 48 glass resistive plate chambers and contains more than 440000 electronic readout channels. This technological calorimeter is often tested with beam of particles at CERN. The collected allowed me to study the hadronic showers with many details. Methods to reconstruct precisely the hadronic showers energy has been developed in order to improve the SDHCAL energy resolution. My main contribution was the development of the hadronic shower simulation within the SDHCAL. A realistic simulation of the SDHCAL was performed by studying the SDHCAL response to the passage of muons and electromagnetic showers. I was then able to compared different simulation models with experimental data. The SDHCAL granularity allows precise studies on the hadronic showers topology, such as longitudinal and lateral shower extent. I finally worked on the W and Z boson mass reconstruction in a full simulation of the International Large Detector in order to study the performance of this calorimeter option with particle flow techniquesLe Collisionneur Linéaire International ILC est un projet de collisionneur électron-positon développé pour prendre le relais du Grand Collisionneur de Hadrons LHC. Ce projet permettra d'étudier précisément les caractéristiques du nouveau boson de 125 GeV , découvert en 2012 par les expérience CMS et ATLAS, compatible avec le boson de Higgs du modèle standard. Cette expérience pourrait aussi permettre aux physiciens de mettre à jour des phénomènes physiques inconnus. Pour exploiter au maximum ce nouvel accélérateur, deux collaborations travaillent sur le développement de deux détecteurs : le Grand Détecteur International ILD et le Détecteur au Silicium SiD. Ces détecteurs sont dits généralistes et sont optimisés pour la mise en oeuvre de technique de suivi des particules. Ils sont constitués d'un trajectographe dans leur partie centrale et de systèmes de calorimétrie. L'ensemble est inséré dans un aimant supraconducteur, lui même entouré d'une culasse instrumentée avec des chambres à muon. Le groupe lyonnais dans lequel j'ai effectué mes travaux de recherche pendant mon doctorat, a grandement participé au développement du calorimètre hadronique à lecture semi-digitale. Ce calorimètre ultra-granulaire fait partie des options pour le calorimètre hadronique du Grand Détecteur International. Un prototype a été construit en 2011. D'environ 1 m3, il est constitué de 48 chambres à plaque résistive de verre, comporte plus de 440000 canaux de lecture de 1 cm2 et pèse environ 10 tonnes. Ce calorimètre répond aux contraintes imposées pour le Collisionneur Linaire International (une haute granularité, une consommation électrique faible, une alimentation pulsée etc) et est régulièrement testé sur des lignes de faisceau au CERN. Les données ainsi collectées m'ont permis d'étudier en détail le phénomène de gerbe hadronique. De nombreux efforts ont été réalisé pour développer des méthodes efficace de reconstruction de l'énergie des gerbes hadroniques et pour améliorer la résolution en énergie du prototype SDHCAL. La simulation des gerbes hadroniques dans le SDHCAL constitue une part importante de mes travaux de recherche. Une simulation réaliste des chambres à plaque résistive de verre a été développée en étudiant la réponse du prototype au passage de muons et de gerbes électromagnétiques. J'ai alors confronté les modèles de simulation des gerbes hadroniques avec des données expérimentales. La granularité du SDHCAL rend aussi possible des études fines sur la topologie des gerbes hadroniques, notamment sur leur extension latéraleet longitudinale. J'ai finalement pu étudier, en m'appuyant sur mes travaux de simulations, la reconstruction de la masse des bosons W et Z dans une simulation complète du Grand Détecteur International. Cette étude permet d'estimer les performances de l'ILD avec le SDHCAL et les techniques de suivi des particule

High rate, fast timing Glass RPC for the high η\eta CMS muon detectors

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to $6 \cdot 10^{34}$ cm$^{-2}$s$^{-1}$. The region of the forward muon spectrometer ($|\eta| > 1.6$) is not equipped with RPC stations. The increase of the expected particles rate up to 2 kHz/cm$^2$ ( including a safety factor 3 ) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The actual RPC technology of CMS cannot sustain the expected background level. A new generation Glass-RPC (GRPC) using low resistivity glass (LR) is proposed to equip at least the two most far away of the four high eta muon stations of CMS. The design of small size prototypes and the studies of their performances under high rate particles flux is presented.Comment: 5 pages, 5 figures, proceeding for the conference VCI 201

Cluster temperature profiles and Sunyaev-Zeldovich observations

Galaxy clusters are not iso-thermal, and the radial temperature dependence will affect the cluster parameters derived through the observation of the Sunyaev-Zeldovich (SZ) effect. We show that the derived peculiar velocity will be systematically shifted by 10-20%. For future all-sky surveys one cannot rely on the observationally expensive X-ray observations to remove this systematic error, but one should instead reach for sufficient angular resolution to perform a deprojection in the SZ spectra. The Compton weighted electron temperature is accurately derived through SZ observations.Comment: 4 pages, 1 figure, minor typos correcte

Retrieval of snow properties from the Sentinel-3 Ocean and Land Colour Instrument

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing. In this work, we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400–1020 nm, we derived important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on a spatial grid of 300 m. The algorithm also incorporated cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long-term snow property records essential for climate monitoring and data assimilation studies—especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.publishedVersio

Extraction of cluster parameters with future Sunyaev-Zel'dovich observations

The Sunyaev-Zel'dovich (SZ) effect of galaxy clusters is characterized by three parameters: Compton parameter, electron temperature and cluster peculiar velocity. In the present study we consider the problem of extracting these parameters using multi-frequency SZ observations only. We show that there exists a parameter degeneracy which can be broken with an appropriate choice of frequencies. As a result we discuss the optimal choice of observing frequencies from a theoretical point of view. Finally, we analyze the systematic errors (of the order micro K) on the SZ measurement introduced by finite bandwidths, and suggest a possible method of reducing these errors.Comment: 20 pages, 13 figures, to be published in JCA

Novel mutation in the CHST6 gene causes macular corneal dystrophy in a black South African family

BACKGROUND: Macular corneal dystrophy (MCD) is a rare autosomal recessive disorder that is characterized by progressive corneal opacity that starts in early childhood and ultimately progresses to blindness in early adulthood. The aim of this study was to identify the cause of MCD in a black South African family with two affected sisters. METHODS: A multigenerational South African Sotho-speaking family with type I MCD was studied using whole exome sequencing. Variant filtering to identify the MCD-causal mutation included the disease inheritance pattern, variant minor allele frequency and potential functional impact. RESULTS: Ophthalmologic evaluation of the cases revealed a typical MCD phenotype and none of the other family members were affected. An average of 127 713 variants per individual was identified following exome sequencing and approximately 1.2 % were not present in any of the investigated public databases. Variant filtering identified a homozygous E71Q mutation in CHST6, a known MCD-causing gene encoding corneal N-acetyl glucosamine-6-O-sulfotransferase. This E71Q mutation results in a non-conservative amino acid change in a highly conserved functional domain of the human CHST6 that is essential for enzyme activity. CONCLUSION: We identified a novel E71Q mutation in CHST6 as the MCD-causal mutation in a black South African family with type I MCD. This is the first description of MCD in a black Sub-Saharan African family and therefore contributes valuable insights into the genetic aetiology of this disease, while improving genetic counselling for this and potentially other MCD families. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12881-016-0308-0) contains supplementary material, which is available to authorized users

Role of mprF1 and mprF2 in the Pathogenicity of Enterococcus faecalis

Aujourd hui, Enterococcus faecalis est considéré comme l un des plus importants agents pathogènes causant des maladies nosocomiales. En raison de sa résistance innée et acquise aux antibiotiques, l identification de nouvelles cibles pour le traitement de cette bactérie est une grande priorité. Le facteur Multiple Peptide Résistance (MprF), qui a été décrit en premier chez Staphylococcus aureus, modifie le phosphatidylglycérol avec de la lysine et réduit ainsi la charge négative de l enveloppe cellulaire. Ceci a comme conséquence d augmenter la résistance aux peptides antimicrobiens cationiques (PAC). Deux gènes paralogues putatifs (mprF1 et mprF2) ont été identifiés chez E. faecalis par recherche BLAST en utilisant le gène décrit chez S. aureus. Une caractérisation de ces deux gènes d E. faecalis ainsi que des mécanismes conduisant à une résistance aux PAC, pourrait aider à développer des nouvelles stratégies thérapeutiques contre ce pathogène. Deux mutants de délétion et un double mutant ont été construits par recombinaison homologue chez E. faecalis. L analyse des phospholipides des membranes cytoplasmiques des deux mutants mprF1 et mprF2 par chromatographie sur couche mince a montré que seule l inactivation de mprF2 inhibe la synthèse de trois amino-phosphatidlyglycérol distincts (comme la Lysine-PG, l Alanine-PG et l Arginine-PG). De plus, le mutant mprF2 est également plus sensible aux PAC que la souche sauvage. La capacité de formation d un biofilm est généralement considérée comme un facteur important de virulence, ce qui est également le cas pour les entérocoques. Le mutant mprF2 montre une capacité accrue dans ce phénomène. Ceci semble être du à une augmentation de la concentration d ADN extracellulaire dans le biofilm formé par ce mutant. Curieusement, cette augmentation est indépendante d une autolyse. Le mutant mprF2 est également plus résistant à l opsonophagocytose. Cependant, le gène mprF2 ne joue aucun rôle dans les bactériémies de souris et les endocardites de rats.En revanche, aucun phénotype n a été trouvé pour un mutant mprF1 jusqu à présent. Cette mutation ne modifie ni la synthèse de l aminoacyl-PG en condition de laboratoire ni la résistance aux PAC et à l opsonophagocytose. Par conséquent, il semble que mprF2 soit le seul gène mprF fonctionnel chez E. faecalis. Néanmoins, contrairement à d autres bactéries, mprF2 ne semble pas être un facteur de virulence majeur pour cette espèce.Enterococcus faecalis is regarded nowadays as one of the most important nosocomial pathogens. Due to its innate and acquired resistance to antibiotics, identification of new targets for antimicrobial treatment of E. faecalis is a high priority. The multiple peptides resistance factor (MprF), which was first described in Staphylococcus aureus, modifies phosphatidylglycerol with lysine and reduces the negative charge of the membrane, thus increasing resistance to cationic antimicrobial peptides (CAMPs). Two putative mprF paralogs (mprF1 and mprF2) were identified in E. faecalis by Blast search using the well-described S. aureus gene as a lead. A better understanding of these two genes and mechanisms leads to enterococcal resistance to CAMPs might help designing therapeutic strategies against this bacteria. Two single deletion mutants and double mutant in E. faecalis were created by homologues recombination. Analysis of cell membrane phospholipids from both mutants by thin-layer chromatography showed that inactivation of mprF2 abolished the synthesis of three distinct amino-phosphatidylglycerol (mostly likely Lysin-PG, Alanine-PG and Argine-PG). The CAMPs testing assay demonstrated that the deletion mutant of mprF2 was more susceptible to CAMPs than the wild type. Biofilm formation is usually regarded as a virulence factor which provides an important way for enterococci to cause infections. Inactivation of mprF2 led to increase the biofilm formation which we showed that it was due to the accumulation of eDNA in the biofilm, but the release of eDNA is independent from autolysis. The mprF2 mutant was resistance to killing by opsonophagocytosis more than wild type. However, the mprF2 gene plays no role in bacteremia in mice and rat endocarditis. Our results showed that non polar effect mprF1 mutant does not affect in the synthesis of aminoacyl-PG in the laboratory condition. It also has no effect on susceptible to CAMPs, opsonic killing and autolysis. Therefore, it seems that mprF2 is the only functional mprF gene in E. faecalis in the laboratory condition. Unlike mprF found in other bacteria, mprF does not seem to be a major virulence factor in enterococci.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF