The performance of hadronic calorimeters will be a key parameter at the next generation of High Energy Physics accelerators. A detector combining fine granularity with excellent timing information ...would prove beneficial for the reconstruction of both jets and electromagnetic particles with high energy resolution. In this work, the space and time structure of high energy showers is studied by means of a Geant4-based simulation toolkit. In particular, the relevant time scales of the different physics phenomena contributing to the energy loss are investigated. A correlation between the fluctuations of the energy deposition of high energy hadrons and the time development of the showers is observed, which allows for an event-by-event correction to be computed to improve the energy resolution of the calorimeter. These studies are intended to set the basic requirements for the development of a new-concept, total absorption time-imaging calorimeter, which seems now within reach thanks to major technological advancements in the production of fast scintillating materials and compact photodetectors.
The high energy physics community has recently identified an e+e− Higgs factory as one of the next-generation collider experiments, following the completion of the High Luminosity LHC program at ...CERN. The moderate radiation levels expected at such colliders compared to hadron colliders, enable the use of less radiation tolerant but cheaper technologies for the construction of the particle detectors. This opportunity has triggered a renewed interest in the development of scintillating glasses for the instrumentation of large detector volumes such as homogeneous calorimeters. While the performance of such scintillators remains typically inferior in terms of light yield and radiation tolerance compared to that of many scintillating crystals, substantial progress has been made over the recent years. In this paper we discuss the time resolution of cerium-doped Alkali Free Fluorophosphate scintillating glasses, read-out with silicon photo-multipliers in detecting single charged tracks and at different positions along the longitudinal development of an electromagnetic shower, using respectively 150 GeV pions and 100 GeV electron beams at the CERN SPS H2 beam line. A single sensor time resolution of 14.4 ps and 5–7 ps was measured respectively in the two cases. With such a performance the present technology has the potential to address an emerging requirement of future detectors at collider experiments: measuring the time-of-flight of single charged particles as well as that of neutral particles showering inside the calorimeter and the time development of showers.
The electromagnetic calorimeter (ECAL) of the CMS experiment at the CERN Large Hadron Collider is a hermetic, fine grained, homogeneous calorimeter containing 75848 lead tungstate crystals, completed ...by a silicon preshower installed in front of the endcaps. The main characteristics of the ECAL are reviewed. These include the challenges of calibration and triggering in the LHC environment, as well as the reconstruction and identification of photons and electrons. Several results achieved by the CMS experiment particularly exploit the ECAL excellent performance, here illustrated with reference to specific examples, comprising the Higgs boson search and characterization in the H arrow right gamma gamma and H arrow right ZZ super((*)) decay channels and the search for non-standard phenomena such as high-mass gauge bosons decaying into electrons and long-lived particles with delayed signals in the calorimeter.
CMS results are presented on the measurement of properties of the Higgs-like particle discovered last summer with a mass in the range of 125-126 GeV, based on the full statistics of about 25 fb ...super(?1), collected in 2011 and 2012 at 7 and 8 TeV respectively. Five decay channels are considered for these studies, namely the ZZ, yy, WW, TT, and bb modes. The mass of the new boson is measured to be 125.7 + or - 0.4 GeV. The event yields measured by the different analyses, targeting specific decay modes and production mechanisms, are consistent with those expected for the standard model (SM) Higgs boson, with an overall best-fit signal strength of 0.80 + or - 0.14 at the measured mass. A discussion on the measurement of the couplings and the spin-parity properties of this new particle is presented, using
The high energy physics community has recently identified an \(e^+e^-\) Higgs factory as one of the next-generation collider experiments, following the completion of the High Luminosity LHC program ...at CERN.The moderate radiation levels expected at such colliders compared to hadron colliders, enable the use of less radiation tolerant but cheaper technologies for the construction of the particle detectors. This opportunity has triggered a renewed interest in the development of scintillating glasses for the instrumentation of large detector volumes such as homogeneous calorimeters. While the performance of such scintillators remains typically inferior in terms of light yield and radiation tolerance compared to that of many scintillating crystals, substantial progress has been made over the recent years. In this paper we discuss the time resolution of cerium-doped Alkali Free Fluorophosphate scintillating glasses, read-out with silicon photo-multipliers in detecting single charged tracks and at different positions along the longitudinal development of an electromagnetic shower, using respectively 150~GeV pions and 100~GeV electron beams at the CERN SPS H2 beam line. A single sensor time resolution of 14.4~ps and 5-7~ps was measured respectively in the two cases. With such a performance the present technology has the potential to address an emerging requirement of future detectors at collider experiments: measuring the time-of-flight of single charged particles as well as that of neutral particles showering inside the calorimeter and the time development of showers.
Cette thèse présente le travail de trois ans effectué dans l'expérience CMS, dans le contexte des premières collisions proton-proton du LHC. L'étude porte en particulier sur la recherche du boson de ...Higgs. Cette particule, dont l'existence est prévue par le Modèle Standard, n'a encore jamais été observée, mais elle est toujours activement l'objet de recherches auprès de collisionneurs à très hautes énergies. Dans le passé récent, les expériences au LEP et Tevatron ont permis d'exclure l'existence du Higgs dans les domaines de masse < 114 GeV/c2 et 147, 179 GeV/c2, avec un intervalle de confiance de 95%. Au moment où le sujet de cette thèse a été décidé, les domaines de masse très faible et très élevé étaient donc les régions les plus intéressantes. Avec les données de collisions de 2011, je me suis occupé de la question de la stabilité et uniformité de la réponse du calorimètre électromagnétique (ECAL). Des électrons isolés, provenant de la désintégration de boson W en en voie électron-neutrino ont été utilisé pour caractériser la réponse du ECAL (corrections locales d'uniformité, corrections de transparence des cristaux, vieillissement des cellules de lecture). Ceci sert de référence pour l'analyse du Boson du Higgs se désintégrant en deux photons, qui est le canal favori pour des hypothèses de masse faible et qui exige une une résolution en énergie optimale pour mieux profiter de la résonance trés étroite du boson du Higgs pour ces masses. L'analyse de physique effectuée dans cette thèse porte sur la recherche de bosons de Higgs dans l'autre région de masse encore permise par les contraintes expérimentales. En particulier, j'ai étudié le canal de désintégration H > WW > lνqq pour des masses du Higgs mH > 2mW. Ce canal est celui qui offre la plus grande section efficace de production (σ × B) pour le boson de Higgs, même s'il est pénalisé par des bruits de fonds de processus standards importants. Une stratégie d'analyse complète a été définie: j'ai étudié les performances pour la physique de la reconstruction et de l'identification des leptons isolés, fortement contribué à la définition et à la caractérisation du déclenchement (trigger) pour ce canal, et procédé à une analyse détaillée des sources d'incertitudes systématiques affectants l'interprétation statistique des résultats. En absence d'une déviation par rapport à l'attendue des bruits de fonds du modèle standard, des limites supérieures sur la masse du boson de Higgs ont été obtenu, entre 320 et 400 GeV/c2 environ.
Orientador : Aluisio de Souza Pinheiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
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Previous issue date: 2004
Mestrado
Mestre em Estatística
Available evidence on the impact of ovarian stimulation on the progression of endometriosis or its recurrence was systematically reviewed. Data from ovarian stimulation alone, or associated with ...intrauterine insemination (IUI) or IVF, were included. Sixteen studies were selected. Initial case reports (n = 11) documented some severe clinical complications. However, subsequent observational studies were more reassuring. Overall, five conclusions can be drawn: (i) IVF does not worsen endometriosis-related pain symptoms (moderate quality evidence); (ii) IVF does not increase the risk of endometriosis recurrence (moderate quality evidence); (iii) the impact of IVF on ovarian endometriomas, if present at all, is mild (low quality evidence); (iv) IUI may increase the risk of endometriosis recurrence (low quality evidence); (v) deep invasive endometriosis might progress with ovarian stimulation (very low quality evidence). In conclusion, available evidence is generally reassuring (at least for IVF) and does not justify aggressive clinical approaches such as prophylactic surgery before assisted reproductive technology treatment to prevent endometriosis progression or recurrence. However, further evidence is required before being able to reach definitive conclusions. In particular, the potential effects on deep invasive endometriosis and the possible synergistic effect of stimulation and pregnancy are two areas that need to be explored further.
The enantioselective organocatalytic reduction of trifluoromethyl aryl and alkyl ketoimines afforded the corresponding fluorinated amines with high chemical and stereochemical efficiency. The Lewis ...base catalyzed reaction with trichlorosilane led to chiral products with a trifluoromethyl group directly linked to the newly generated stereocenter typically in >90% yield and up to 98% e.e.
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