1,721,116 research outputs found
Sensitivity of the KM3NeT/ORCA detector to the neutrino mass ordering and beyond
No full textThe KM3NeT collaboration is currently building a new generation of large-volume water-Cherenkov neutrino telescopes in the Mediterranean sea. Two detectors, ARCA and ORCA, are under construction. They feature different neutrino energy thresholds: TeV range for ARCA and GeV range for ORCA. The main research goal of ORCA is the measurement of the neutrino mass ordering and atmospheric neutrino oscillation parameters, while the detector is also sensitive to a wide variety of other physics topics, including non-standard interactions, sterile neutrinos and Earth tomography, as well as low-energy neutrino astronomy.
This contribution will present an overview of the updated ORCA sensitivity projection to its main science objectives, including - but not limited to - the measurement of the neutrino mass ordering and oscillation parameters Future perspectives for ORCA to serve as far detector for a long baseline neutrino experiment with a neutrino beam from the U70 accelerator complex at Protvino in Russia will also be discussed
Épreuve expérimentale de la technique du neutrino tagging à NA62
No full textCe travail de thèse s'inscrit dans le cadre de la physique des neutrinos aux accélérateurs. Dans ce contexte, une technique innovante est proposée, qui permettra de réduire significativement les incertitudes systématiques liées aux études des oscillations des neutrinos: la technique du neutrino tagging. Cette technique propose d'instrumenter une ligne de faisceau de neutrinos avec des détecteurs en silicium, afin de reconstruire cinématiquement les propriétés de chaque neutrino du faisceau produits dans les désintégrations pi^pm to mu^pm nuan_mu, K^pm to mu^pm nuan_mu. Le flux initial de neutrinos est donc précisement déterminé et l'énergie individuelle des neutrinos est reconstruite avec une résolution meilleure que 1%. De plus, grâce aux coincidences temporelles et angulaires, les neutrinos reconstruits cinématiquement par les trajectographes peuvent être associés individuellement aux neutrinos interagissant dans le détecteur de neutrinos. La mesure précise de leurs propriétés peut donc être utilisée pour des analyses de physique (par exemple, des oscillations, des sections efficaces). L'objectif principal de ce travail est de démontrer la faisabilité de la technique du neutrino tagging. La preuve de principe de cette méthode a été réalisée en utilisant l'expérience NA62 au CERN comme expérience de physique de neutrinos en miniature: son intense faisceau de kaons chargés produit des neutrinos lors de leur désintégration en K^+ to mu^+ nu_mu, ses spectromètres reconstruisent les propriétés des particules chargées, et son calorimètre électromagnétique sert de détecteur de neutrinos. La mise en œuvre de la technique du neutrino tagging dans le cadre d'une expérience de neutrinos à longue ligne de base est décrite en détail, de même que l'analyse en aveugle effectuée sur les données de NA62. Au terme de l'analyse, deux candidats neutrinos taggués ont été observés, démontrant ainsi la faisabilité de cette technique. Enfin, l'analyse des données provenant d'un test sur faisceau effectué sur des modules basés sur la technologie du GigaTracKer de NA62, visant à étudier la résolution temporelle dans les détecteurs en pixels de silicium, est présentée.This thesis work objectives belong to the framework of neutrino physics at accelerators. In this context, an innovative technique is proposed, that will substantially reduce the systematic uncertainties linked to the neutrino oscillation studies: the neutrino tagging technique. The neutrino tagging technique proposes to instrument a neutrino beam line with silicon trackers to kinematically reconstruct properties of individual beam neutrinos produced in pi^pm to mu^pm nuan_mu, K^pm to mu^pm nuan_mu decays.As a result, the initial neutrino flux is precisely determined and the individual neutrino energy can be reconstructed with a resolution better than 1%. Moreover, based on time and angular coincidence, the neutrinos kinematically reconstructed by the trackers can be individually associated to the neutrinos interacting in the neutrino detector, such that the precise measurement of their properties can be used for physics analyses (e.g. oscillations, cross-section).The main aim of this work is to demonstrate the feasibility of the neutrino tagging technique.The proof of principle of the neutrino tagging method has been performed using the NA62 experiment at CERN as a miniature neutrino experiment: its intense kaon beam copiously produces neutrinos when decaying as K^+ to mu^+ nu_mu, its spectrometers act as tagger for the charged particles, and its electromagnetic calorimeter serves as neutrino detector. The implementation of the neutrino tagging at a Long Baseline Neutrino Experiment is described in detail, as well as the blind analysis performed on NA62 data. Two tagged neutrino candidates are found in the signal region, proving the feasibility of this technique. Finally, the data analysis on the data from a test beam performed on modules based on the NA62 GigaTracKer technology, aimed to study the time resolution budget in silicon pixel detectors, is presented
Search for and
No full textWithin the Standard Model (SM), the two flavour changing neutral current transitions, and , occur only via loop diagrams and are helicity suppressed. These processes are therefore very rare with branching fractions () predictions [1] of =(0.32 0.2)x 10 and =(0.0100.001)x 10. These precise predictions allow the SM to be tested against New Physics scenarios, for example the Minimal Supersymmetric SM [2], in which are significantly enhanced. The most restrictive experimental preliminary limits obtained by CDF [4]} are: <4.3 x 10 and <0.76 x 10 at 95% confidence level (C.L.). The 37 pb of data collected by the LHCb detector [3] already allow for upper limits to be set close to the world best ones
Searches for B meson decays to purely leptonic final states
No full textThe decays are helicity suppressed and process through flavour changing neutral currents. They are extremely rare in the standard model (SM). Thus physics beyond SM could modify their branching ratio up to an observable level. As the theoretical predictions are very precise, these modes are golden channels to probe the SM. The works presented in this thesis have contributed to the establishment of the first evidence of the decay. A statistical method has been built to extract and combine limits on the decays branching fraction and to compute signals significance. On the basis of this work, an original method was developed to re-optimised the categories used to classified the candidates which improved the analysis sensitivity by 14%. A study of the interplay between the flavour mixing of the and its decay demonstrated that the analysis results are model dependent. Accounting for this dependency allows to improve constraints on new physics. Finally, an inclusive topological reconstruction was developed and tested in particular to reconstruct candidates with
Searches for B meson decays to purely leptonic final states in LHCb
No full textLes désintégrations B->l l sont supprimées d'hélicité et se produisent à travers des courants neutres changeant la saveur. Elles sont donc extrêmement rares dans le modèle standard (MS). La physique au-delà du MS pourrait donc modifier substantiellement la valeur des rapports d'embranchement prédits par le MS. Ces prédictions étant très précises, mesurer leur valeurs constitue un test incontournable du MS.Les travaux présentés dans cette thèse ont contribué à l'établissement de la première évidence de la désintégration Bs->mu mu avec LHCb. Une méthode statistique a ete développée pour extraire et combiner les limites sur les rapports d'embranchement et calculer la signifiance des signaux. A partir de ces acquis statistiques, une méthode originale a été conçue pour re-optimiser les catégories dans lesquelles les candidats sont classés améliorant ainsi la sensibilité de l'analyse de 14%. D'autre part, une étude sur la phénoménologie des interférences entre le mélange de saveur des mésons Bs et leur désintégration a mis en évidence une subtile dépendance de l'analyse avec le modèle physique considéré. La prise en compte de cette dépendance permet de contraindre plus fortement la nouvelle physique. Enfin une méthode de reconstruction topologique inclusive des évènements a été développée et testée, notamment pour reconstruire les candidats Bs->tau tau avec tau->pi pi pi nu.The B->l l decays are helicity suppressed and process through flavour changing neutral currents. They are extremely rare in the standard model (SM). Thus physics beyond SM could modify their branching ratio up to an observable level. As the theoretical predictions are very precise, these modes are golden channels to probe the SM.The works presented in this thesis have contributed to the establishment of the first evidence of the Bs->mu mu decay. A statistical method has been built to extract and combine limits on the decays branching fraction and to compute signals significance. On the basis of this work, an original method was developed to re-optimised the categories used to classified the candidates which improved the analysis sensitivity by 14%. A study of the interplay between the flavour mixing of the Bs and its decay demonstrated that the analysis results are model dependent. Accounting for this dependency allows to improve constraints on new physics. Finally, an inclusive topological reconstruction was developed and tested in particular to reconstruct Bs->tau tau candidates with tau->pi pi pi nu
Tagged Neutrino Beams
No full textThis article describes a new experimental method for accelerator based neutrino experiments called neutrino tagging. The method consists in exploiting the neutrino production mechanism, the π± → µ± νµ decay, to kinematically reconstruct the neutrino properties from the decay incoming and outgoing charged particles. The reconstruction of these particles relies on the recent progress and ongoing developments in silicon particle detector technology. A description of the method is presented, together with its potential benefits for short and long baseline experiments. Then, a novel configuration for long baseline experiments is discussed in which a tagged beam would be employed together with megaton scale natural deep water Cherenkov detectors. The coarseness of this type of detectors is overcome by the precision of the tagging and, conversely, the rate limitation imposed by the tagging is outweighed by the size of the detector. These mutual benefits result in an affordable design for next generations of long based line experiments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
